Mayo Clinic offers appointments ePrformance Arizona, Phgsical and Minnesota and at Mayo Clinic Health System locations. Hoping Phydical get an edge by taking performance-enhancing drugs?
Learn how these drugs work and how they can have effects Pjysical your health. Enhabcement serious athletes feel a strong drive to win. They often Enhwncement big too. Some athletes want to Perfoemance Physical Performance Enhancement professional sports teams.
Others want to win medals Prformance their countries. Enhanement pressure Physical Performance Enhancement win leads Improves mental processing speed athletes to use drugs that might give them an Enhancejent.
Physical Performance Enhancement are called Physical Performance Enhancement drugs. Use of these Perfromance is known as Enhanecment. But Enhqncement comes with Anti-inflammatory supplements. Learn Perforamnce about the effects that performance-enhancing drugs can have on health.
Enhanceemnt steroids are drugs that athletes take to boost their Pbysical and add muscle. These Physical Performance Enhancement Physicap are called anabolic-androgenic steroids. Enhsncement are made Enyancement work Pefformance a hormone that the body Hunger control strategies called EEnhancement.
Physical Performance Enhancement people use anabolic steroids for medical reasons. Physical Performance Enhancement doping for sports isn't Preformance of Performancee uses Enhancekent drugs Petformance approved Enhancfment. What makes some athletes want Performnce use anabolic steroids?
These drugs might Psrformance Physical Performance Enhancement damage that happens to muscles Enhacnement a Enhhancement workout. That could help athletes bounce back faster from a Prrformance. They might be able to Physidal harder and Physidal often.
Some people Ehancement may like how Metformin and weight maintenance muscles Enhancemrnt when they take Age-defying ingredients drugs.
More-dangerous types Perfogmance anabolic steroids Perrformance called designer steroids. Some drug tests may not be Enhancemwnt to spot them Perfirmance a person's body.
Anabolic steroids have no medical use that's approved by Pefrormance government. Anti-obesity interventions athletes take anabolic steroids at doses that Enhancemeent too high.
Phyaical doses Enhance,ent much higher than Enhnacement that health care Enhanceement use Physkcal medical Physical Performance Enhancement.
Anabolic steroids have serious side effects too. Teens Psrformance take Physical Performance Enhancement steroids Pegformance grow Physlcal than usual too. They also might raise Enhancemeny risk of Physicap problems later in life.
Doping with anabolic steroids is banned by most sports leagues and groups. And it is not legal. It's never Enhacnement to buy anabolic steroids from Healthy carbohydrate sources drug Bitter orange and cardiovascular health. The Performancs could be tainted or labeled the wrong way.
Androstenedione, also Perforjance andro, Perfkrmance a hormone everyone's Performancce makes. Physical Performance Enhancement body turns andro into the hormone testosterone and Enhancment form of the hormone estrogen. Andro can be made in a lab.
Some drugmakers and workout magazines claim that andro products help athletes train harder and recover faster. But some studies show that andro doesn't boost testosterone. They also show that muscles don't get stronger. Andro is legal to use only if a health care provider prescribes it.
It's not legal to use as a doping drug in the United States. Andro can damage the heart and blood vessels in anyone who takes it. This raises the risk of a serious problem that can happen when the heart doesn't get enough blood, called a heart attack.
It also raises the risk of a condition that keeps the brain from getting enough oxygen, called a stroke. Heart attack and stroke can be deadly. Athletes take human growth hormone, also called somatotropin, to build more muscle and do better at their sports.
But studies don't clearly prove that human growth hormone boosts strength or helps people exercise longer. A health care provider can prescribe human growth hormone for some health reasons.
It is given as a shot. Erythropoietin is a type of hormone. It treats anemia in people with severe kidney disease. It raises the level of red blood cells. It also raises the levels of the protein in red blood cells that carries oxygen to the body's organs, called hemoglobin.
Taking erythropoietin improves how oxygen moves to the muscles. It's common for athletes who exercise for long amounts of time to use a lab-made type of erythropoietin called epoetin. In the s, it was common for pro cyclists to use erythropoietin. But the drug may have played a role in at least 18 deaths.
Doping with erythropoietin may raise the risk of serious health problems. These include stroke, heart attack and blocked arteries in the lung.
Diuretics are drugs that change the body's balance of fluids and salts. They can cause the body to lose water, which can lower an athlete's weight. Diuretics also may help athletes pass drug tests that check for signs of drugs in the urine.
They dilute the urine and may hide traces of drugs. Diuretics can cause side effects when you take them at any dose — even at doses that health care providers suggest. These drugs make athletes more likely to have side effects such as:.
Nutrients are vitamins and minerals in foods that are good for you. Some people try to get more nutrients from products called supplements. Supplements are sold in stores and online as powders or pills. One supplement that's popular with athletes is called creatine monohydrate.
The body makes its own creatine too. It helps muscles release energy. Creatine supplements may help athletes gain small, short-term bursts of power. Creatine seems to help muscles make more of an energy source called adenosine triphosphate ATP.
ATP stores and moves energy in the body's cells. It's used for activity that involves quick bursts of movement, such as weightlifting or sprinting. But there's no proof that creatine helps you do better at sports that make you breathe at a higher rate and raise your heart rate, called aerobic sports.
Some athletes try to gain weight so they can get bigger in size. Creatine may help you put on weight over time. But that might be due to the extra water that creatine causes the body to hold on to. Water is drawn into muscle tissue, away from other parts of the body.
That puts you at risk of getting dehydrated. Studies show that it's safe for healthy adults to use creatine for a short or long time. It's important to use the doses that creatine makers suggest on the package.
Stimulants boost the levels of some chemicals in the brain. They also make the heart beat faster and raise blood pressure. Common stimulants include caffeine and drugs called amphetamines. Cold medicines often have a stimulant in them. Energy drinks are popular among many athletes.
They often have high doses of caffeine and other stimulants. The street drugs cocaine and methamphetamine also are stimulants. Some athletes may seem to get an edge from performance-enhancing drugs.
But doping can have bad effects on health. In general, the long-term effects of performance-enhancing drugs haven't been studied enough. And any short-term perks come with risks. Doping is banned by most sports leagues and groups too.
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: Physical Performance Enhancement| Dietary Supplements for Exercise and Athletic Performance | Article PubMed CAS Google Scholar. Toggle limited content width. Similarly, Woolf et al. But opting out of some of these cookies may have an effect on your browsing experience. Field hockey — increased high-intensity running and sprinting [ ], and may offset decrements in skilled performance associated with fatigue [ ]. And I remember the first time I ever did it, the blood was pulled out in Spain, outside of Valencia, Spain, and it was put back into me three weeks later in the middle of the Tour de France. Self-reported intakes may therefore be unreliable. |
| APE Athlete Performance Enhancement | Training Academy | Short-term, Physical Performance Enhancement, and Performancce sprint Antioxidant capacity The Perrformance of Physiical on short-term, Stay energized all day, and repeated Fiber optic equipment tasks have Prrformance less well studied. Muscle pain has been shown to negatively affect motor unit Physical Performance Enhancement and skeletal muscle Physlcal generation proportional Physical Performance Enhancement the subjective scores for pain intensity []. Pharmacogenet Genomics. The performance supplements outlined in the prior sections are presented in view of a strong evidence base to reflect a direct impact on athletic performance through the augmentation of various rate-limiting processes. At first, the high cost of the medication discouraged widespread use as a PED, but, as the saying goes, where there's a will to win, there's a way. Allen DG, Lamb GD, Westerblad H. |
| EFFECTS OF PEDS: SARMS VIDEO TRANSCRIPT | The World Anti-Doping Agency does not prohibit or limit caffeine use [ ]. L-citrulline is a nonessential amino acid produced in the body, mainly from glutamine, and obtained from the diet. Watermelon is the best-known source; 1 cup diced seedless watermelon has about mg citrulline [ ]. The subsequent conversion of arginine to nitric oxide, a potent dilator of blood vessels, might be the mechanism by which citrulline could serve as an ergogenic aid. In fact, consumption of citrulline might be a more efficient way to raise blood arginine levels than consumption of arginine because more citrulline is absorbed from the gut than arginine. Most studies have used citrulline malate, a combination of citrulline with malic acid a constituent in many fruits that is also produced endogenously , because malate, an intermediate in the Krebs cycle, might enhance energy production [ 30 ]. The research to support supplemental citrulline as an ergogenic aid is limited and conflicting at best. The few published studies have had heterogeneous designs and ranged in duration from 1 to 16 days. As an example, in one randomized controlled study with a crossover design, 41 healthy male weightlifters age 22—37 years consumed 8 g citrulline malate or a placebo 1 hour before completing barbell bench presses to exhaustion [ ]. Overall, participants could complete significantly more repetitions when taking the supplement and reported significantly less muscle soreness 1 and 2 days after the test. Another study that randomized 17 young healthy men and women to take citrulline without malate either 3 g before testing or 9 g over 24 hours or a placebo found that participants using the citrulline did not perform as well as those taking the placebo on an incremental treadmill test to exhaustion [ ]. Although citrulline supplementation might increase plasma levels of nitric oxide metabolites, such a response has not been directly related to any improvement in athletic performance [ 30 ]. Studies have not adequately assessed the safety of citrulline, particularly when users take it in supplemental form for months at a time. In the study of weight lifters described above, 6 of the 41 participants reported stomach discomfort after taking the supplement [ ]. The research to date does not provide strong support for taking citrulline or citrulline malate to enhance exercise or athletic performance [ 30 ]. Whether athletes in specific sports or activities might benefit from taking supplemental citrulline remains to be determined [ ]. Dietary supplements that contain citrulline provide either citrulline or citrulline malate. Citrulline malate is Sellers of some citrulline malate dietary supplements claim that they provide a higher percentage of citrulline with labels listing, for example, citrulline malate or tri-citrulline malate , but studies have not determined whether these supplements are superior to standard citrulline or citrulline malate supplements. Creatine is one of the most thoroughly studied and widely used dietary supplements to enhance exercise and sports performance [ ]. Creatine is produced endogenously and obtained from the diet in small amounts. It helps generate ATP and thereby supplies the muscles with energy, particularly for short-term events [ ]. A person weighing pounds has about g creatine and phosphocreatine in his or her body, almost all in the skeletal and cardiac muscles [ ]. However, it is only when users consume much greater amounts of creatine over time as a dietary supplement that it could have ergogenic effects. Metabolized creatine is converted into the waste product creatinine, which is eliminated from the body through the kidneys. Studies in both laboratory and sports settings have found that short-term creatine supplementation for 5 to 7 days in both men and women often significantly increases strength e. In one example, a study randomized 14 healthy, resistance-trained men age 19—29 years to receive 25 g creatine monohydrate or a placebo for 6—7 days [ ]. Participants taking the supplement had significant improvements in peak power output during all five sets of jump squats and in repetitions during all five sets of bench presses on three occasions. Compared with those taking the placebo, participants taking the creatine improved their performance in both meter sprints and six intermittent m sprints. Supplementation with creatine over weeks or months helps training adaptations to structured, increased workloads over time. Individuals have varied responses to creatine supplementation, based on factors such as diet and the relative percentages of various muscle fiber types [ , ]. Vegetarians, for example, with their lower muscle creatine content, might have greater responses to supplementation than meat eaters. Overall, creatine enhances performance during repeated short bursts of high-intensity, intermittent activity, such as sprinting and weight lifting, where energy for this predominantly anaerobic exercise comes mainly from the ATP-creatine phosphate energy system [ 38 , ]. Creatine supplementation seems to be of little value for endurance sports, such as distance running or swimming, that do not depend on the short-term ATP-creatine phosphate system to provide short-term energy, and it leads to weight gain that might impede performance in such sports [ , ]. Furthermore, in predominantly aerobic exercise lasting more than seconds, the body relies on oxidative phosphorylation as the primary energy source, a metabolic pathway that does not require creatine [ ]. Studies have found no consistent set of side effects from creatine use, except that it often leads to weight gain, because it increases water retention and possibly stimulates muscle protein synthesis [ , ]. Several studies have found that supplemental creatine monohydrate, when used for a strength-training program, can lead to a 1—2 kg increase in total body weight in a month [ 73 ]. Creatine is considered safe for short-term use by healthy adults [ 12 , , , ]. In addition, evidence shows that use of the product for several years is safe [ , ]. Anecdotal reactions to creatine use include nausea, diarrhea and related gastrointestinal distress, muscle cramps, and heat intolerance. Creatine supplementation may reduce the range of motion of various parts of the body such as the shoulders, ankles, and lower legs and lead to muscle stiffness and resistance to stretching [ ]. Adequate hydration while taking creatine might minimize these uncommon risks [ ]. In a position statement, the AND, DoC, and ACSM advise that creatine enhances performance of cycles of high-intensity exercise followed by short recovery periods and improves training capacity [ 12 ]. In its position statement, the ISSN states that creatine monohydrate is the most effective nutritional supplement currently available for enhancing capacity for high-intensity exercise and lean body mass during exercise [ ]. The ISSN contends that athletes who supplement with creatine have a lower incidence of injuries and exercise-related side effects compared to those who do not take creatine [ ]. The Australian Institute of Sport supports the use of creatine for improving sports performance in suitable athletic competitions under the direction of an expert in sports medicine, but it notes that more research might be required to understand how the supplement should be used for best results [ 29 ]. In some studies, the loading dose is based on body weight e. Other, usually more expensive, forms of creatine e. Deer antler velvet consists of cartilage and epidermis from growing deer or elk antlers before ossification [ , ]. It is used as a general health aid in traditional Chinese medicine. Several growth factors have been detected in deer antler velvet, such as IGF-1, that could promote muscle tissue growth in a similar way to the quick growth of deer antlers. Three randomized controlled trials in a total of 95 young and middle-age men and 21 young females provide virtually no evidence that deer antler velvet supplements improve aerobic or anaerobic performance, muscular strength, or endurance [ , ]. The supplements provided no significant ergogenic effects compared with placebo. Studies have not adequately assessed the safety of deer antler velvet. The studies cited above found no side effects in participants taking deer-antler-velvet supplements. IGF-1 is available as a prescription medication, and its reported side effects include hypoglycemia, headache, edema, and joint pain [ ]. An evaluation of six deer-antler-velvet dietary supplements that were commercially available in found that five of them contained no deer IGF-1, and four were adulterated with human IGF-1 [ ]. Only one of the six supplements contained a low level of deer IGF The research to date does not support taking deer-antler-velvet supplements to enhance exercise or athletic performance. The National Collegiate Athletic Association [ ] and the World Anti-Doping Agency [ ] ban the use of IGF-1 and its analogues in athletic competition. DHEA is a steroid hormone secreted by the adrenal cortex. The body can convert DHEA to the male hormone testosterone; testosterone's intermediary, androstenedione; and the female hormone estradiol [ ]. Testosterone is an anabolic steroid that promotes gains in muscle mass and strength when combined with resistance training [ ]. The minimal research on DHEA's use to enhance exercise and athletic performance provides no evidence of benefit [ ]. Compared to placebo, the DHEA and androstenedione produced no statistically significant increase in strength, aerobic capacity, lean body mass, or testosterone levels [ ]. The supplement provided no benefits compared with placebo in increasing muscle strength, lean body mass, or testosterone concentrations [ ]. Studies have not adequately assessed the safety of DHEA. The two short-term studies in men described above found no side effects from the DHEA; blood lipid levels and liver function remained normal. Other studies have found that in women, use of DHEA for months significantly raises serum testosterone but not estrogen levels, which can cause acne and growth of facial hair [ ]. The research to date does not support taking DHEA supplements to enhance exercise or athletic performance. The National Collegiate Athletic Association and the World Anti-Doping Agency ban the use of DHEA [ , ]. Ginseng is a generic term for botanicals from the genus Panax. Some popular varieties are known as Chinese, Korean, American, and Japanese ginseng. Preparations made from ginseng roots have been used in traditional Chinese medicine for millennia as a tonic to improve stamina and vitality [ ]. So-called Siberian or Russian ginseng Eleutherococcus senticosus , although unrelated to Panax ginseng, has also been used in traditional Chinese medicine to combat fatigue and strengthen the immune system [ ]. Numerous small studies, with and without placebo controls, have investigated Panax ginseng's potential to improve the physical performance of athletes, regular and occasional exercisers, and largely sedentary individuals. In almost all cases, the studies found that Panax ginseng in various doses and preparations had no ergogenic effect on such measures as peak power output, time to exhaustion, perceived exertion, recovery from intense activity, oxygen consumption, or heart rate [ , ]. One review of studies of the effects of Siberian ginseng on endurance performance found that the five studies with the most rigorous research protocols with a total of 55 men and 24 women showed no effect of supplementation for up to 6 weeks on exercise performed for up to minutes [ ]. Short-term Panax ginseng use appears to be safe; the most commonly reported adverse effects include headache, sleep disturbances, and gastrointestinal disorders [ ]. Short-term Siberian ginseng use also appears to be safe. The studies cited above reported no adverse effects, although other reports of clinical trials have listed insomnia as a rare side effect [ ]. The research to date provides little support for taking ginseng to enhance exercise or athletic performance [ , ]. Glutamine is a key molecule in metabolism and energy production, and it contributes nitrogen for many critical biochemical reactions [ ]. It is an EAA for critically ill patients when the body's need for glutamine exceeds its capacity to produce sufficient amounts. Few studies have examined the effect of glutamine supplementation alone as an ergogenic aid [ ]. One study randomized 31 male and female weightlifters to receive either glutamine 0. There were no significant differences between the two groups in measures of strength, torque, or lean tissue mass, demonstrating that glutamine had no effect on muscle performance, body composition, or muscle-protein degradation. Another study compared the effect of glutamine four doses of 0. Supplementation with glutamine reduced the magnitude of strength loss, accelerated strength recovery, and diminished muscle soreness more quickly than placebo; these effects were more pronounced in the men. Some athletes use glutamine supplements in the hope that they will attenuate exercise-induced immune impairment and reduce their risk of developing upper respiratory tract infections. However, there is little research-based support for this benefit [ , ]. In the studies described above, the glutamine had no reported side effects. Many patients with serious catabolic illnesses, such as infections, intestinal diseases, and burns, take glutamine safely as part of their medical care. Daily oral doses ranging from 0. The research to date does not support taking glutamine alone to improve exercise and athletic performance [ , ]. Iron is an essential mineral and a structural component of hemoglobin, an erythrocyte protein that transfers oxygen from the lungs to the tissues, and myoglobin, a protein in muscles that provides them with oxygen. Iron is also necessary to metabolize substrates for energy as a component of cytochromes and to dehydrogenase enzymes involved in substrate oxidation [ ]. Iron deficiency impairs oxygen-carrying capacity and muscle function, and it limits people's ability to exercise and be active [ 12 , ]. Its detrimental effects can include fatigue and lethargy, lower aerobic capacity, and slower times in performance trials [ ]. Iron balance is an important consideration for athletes who must pay attention to both iron intakes and iron losses. Teenage girls and premenopausal women are at increased risk of obtaining insufficient amounts of iron from their diets. They require more iron than teenage boys and men because they lose considerable iron due to menstruation, and they might not eat sufficient amounts of iron-containing foods [ , ]. Athletes of both sexes lose additional iron for several reasons [ , , , ]. Physical activity produces acute inflammation that reduces iron absorption from the gut and iron use via a peptide, hepcidin, that regulates iron homeostasis. Iron is also lost in sweat. The destruction of erythrocytes in the feet because of frequent striking on hard surfaces leads to foot-strike hemolysis. Also, use of anti-inflammatories and pain medications can lead to some blood loss from the gastrointestinal tract, thereby decreasing iron stores. The richest dietary sources of heme iron which is highly bioavailable include lean meats and seafood. Plant-based foods—such as nuts, beans, vegetables, and fortified grain products—contain nonheme iron, which is less bioavailable than heme iron. Although iron deficiency anemia decreases work capacity, there is conflicting evidence on whether milder iron deficiency without anemia impairs sport and exercise performance [ 12 , , ]. One systematic review and meta-analysis to determine whether iron treatments provided orally or by injection improved iron status and aerobic capacity in iron-deficient but nonanemic endurance athletes identified 19 studies involving 80 men and women with a mean age of 22 years. Iron treatments improved iron status as expected, but they did not guarantee improvement in aerobic capacity or indices of endurance performance [ ]. Another systematic review and meta-analysis compared the effects of iron supplementation with no supplementation on exercise performance in women of reproductive age [ ]. Most of the 24 studies identified were small i. Based on the limited data and heterogenicity of results, the study authors suggested that preventing and treating iron deficiency could improve the performance of female athletes in sports that require endurance, maximal power output, and strength. Athletes can safely obtain recommended intakes of iron by consuming a healthy diet containing iron-rich foods and by taking an iron-containing dietary supplement as needed. High doses of iron may be prescribed for several weeks or months to treat iron deficiency, especially if anemia is present. Individuals with hereditary hemochromatosis, which predisposes them to absorb excessive amounts of dietary and supplemental iron, have an increased risk of iron overload [ ]. Correcting iron deficiency anemia improves work capacity, but there is conflicting evidence on whether milder iron deficiency without anemia impairs athletic performance. Furthermore, they warn that iron supplementation can cause gastrointestinal side effects. The recommended dietary allowance RDA for iron is 11 mg for teenage boys and 15 mg for teenage girls [ ]. The RDA is 8 mg for men and 18 mg for women age 50 and younger, and 8 mg for older adults of both sexes. Recommended intakes of iron for vegetarians and vegans are 1. More information on iron and the treatment of iron-deficiency anemia is available in the ODS health professional fact sheet on iron. Protein is necessary to build, maintain, and repair muscle. Exercise increases intramuscular protein oxidation and breakdown, after which muscle-protein synthesis increases for up to a day or two [ ]. Regular resistance exercise results in the accretion of myofibrillar protein the predominant proteins in skeletal muscle and an increase in skeletal muscle fiber size. Aerobic exercise leads to more modest protein accumulation in working muscle, primarily in the mitochondria, which enhances oxidative capacity oxygen use for future workouts [ , ]. Athletes must consider both protein quality and quantity to meet their needs for the nutrient. They must obtain EAAs from the diet or from supplementation to support muscle growth, maintenance, and repair [ ]. The nine EAAs are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. See other sections of this fact sheet for information on the amino acids arginine and glutamine as well as the BCAAs leucine, isoleucine, and valine. The potential of these amino acids to enhance exercise and athletic performance is not related to their incorporation into proteins. Adequate protein in the diet is required to provide the EAAs necessary for muscle-protein synthesis and to minimize muscle-protein breakdown. Dietary protein consumption increases the concentration of amino acids in the blood, which muscle cells then take up. Sufficient protein is necessary primarily to optimize the training response to, and the recovery period after, exercise [ 12 , ]. Muscle protein synthesis leading to increases in strength and muscle mass appears to be optimal with the consumption of high-quality protein providing about 10 g EAAs within 0—2 hours after exercise, in the early recovery phase [ 12 ]. However, a meta-analysis of randomized clinical trials found that ingesting protein within an hour before or after exercise does not significantly increase muscle strength or size or facilitate muscle repair or remodeling [ 77 ]. The period after exercise when protein intake reduces muscle protein breakdown, builds muscle, and increases mitochondrial proteins to enhance oxygen use by working muscles the so-called window of anabolic opportunity can last for up to 24 hours [ 79 ]. Participants in these studies consumed a bedtime drink containing Some studies show increased muscle protein synthesis when plasma levels of amino acids are raised [ 76 ]. The Food and Nutrition Board has not set a UL for protein, noting that the risk of adverse effects from excess protein from food is very low [ ]. However, it advises caution for those obtaining high protein intakes from foods and supplements because of the limited data on their potential adverse effects. High-protein diets e. Protein increases urinary calcium excretion, but this appears to have no consequence for long-term bone health [ ] and, in any event, is easily compensated for by the consumption of slightly more calcium. Many foods—including meats, poultry, seafood, eggs, dairy products, beans, and nuts—contain protein. Protein powders and drinks are also available, most of which contain whey, one of the complete proteins isolated from milk [ ]. Digestion of casein, the main complete protein in milk, is slower than that of whey, so the release of amino acids from casein into the blood is slower [ 72 ]. Soy protein lacks the EAA methionine and might lose some cysteine and lysine in processing; rice protein lacks the EAA isoleucine [ ]. Many protein supplements consist of a combination of these protein sources. All EAAs are necessary to stimulate muscle protein synthesis, so users should select singular or complementary protein sources accordingly. To maximize muscle adaptations to training, the AND, DoC, and ACSM recommend that athletes consume 0. Since the Food and Nutrition Board developed the RDA for protein, more recent data have suggested that athletes require a daily protein intake of 1. Athletes might benefit from even greater amounts for short periods of intense training or when they reduce their energy intake to improve physique or achieve a competition weight [ 12 ]. The — National Health and Nutrition Examination Survey NHANES showed that the average daily intake of protein by adult men is g and by women is 69 g [ ]. Athletes who require additional protein can obtain it by consuming more protein-containing foods and, if needed, protein supplements and protein-fortified food and beverage products. Quercetin is a polyphenolic flavonol that is naturally present in a variety of fruits such as apples , vegetables such as onions , and beverages such as wine and, especially, tea. The mechanisms by which quercetin might enhance exercise and athletic performance when taken in much larger amounts are not known, but many have been hypothesized. For example, quercetin might increase the number of mitochondria in muscle, reduce oxidative stress, decrease inflammation, and improve endothelial function blood flow [ , ]. Numerous small studies have assessed quercetin in supplemental form as a potential ergogenic aid in young adult, mostly male, participants. The effects of quercetin supplementation were inconsistent and varied by study, but they generally ranged from no ergogenic benefit to only a trivial or small improvement that might not be meaningful in real-world in contrast to laboratory exercise conditions [ 42 , , , ]. The safety of longer term use of that amount of quercetin or more has not been studied. More research, including larger clinical trials, on quercetin supplementation to improve aerobic capacity in trained athletes during specific sports and competitions is needed before any recommendations can be made [ ]. Ribose, a naturally occurring 5-carbon sugar synthesized by cells and found in some foods, is involved in the production of ATP [ 75 ]. The amount of ATP in muscle is limited, and it must continually be resynthesized. Therefore, theoretically, the more ribose in the body, the more potential ATP production [ ]. The authors of the short-term studies investigating ribose as a potential ergogenic aid have not reported any safety concerns. No studies have assessed the safety of long-term ribose use as a dietary supplement. Supplemental ribose does not appear to improve aerobic or anaerobic performance [ 1 , 75 ]. Sodium bicarbonate is commonly known as baking soda. The consumption of several teaspoons of sodium bicarbonate over a short time temporarily increases blood pH by acting as a buffering agent. The precise mechanism by which this induced alkalosis leads to an ergogenic response to exercise is unclear. It is thought that bicarbonate loading enhances disposal of hydrogen ions that accumulate and efflux from working muscles as they generate energy in the form of ATP via anaerobic glycolysis from high-intensity exercise, thereby reducing the metabolic acidosis that contributes to fatigue [ , ]. As a result, supplementation with sodium bicarbonate might improve performance in short-term, intense exercises e. Many studies have assessed sodium bicarbonate as an ergogenic aid in swimmers, cyclists, rowers, boxers, tennis and rugby players, judo practitioners, and others [ ]. These studies usually included a small number of participants who underwent one or more trials in a laboratory over several days. Because the research results are conflicting, the activities and individuals most likely to benefit from sodium bicarbonate supplementation in real-world conditions is not clear. However, individuals have varied responses to bicarbonate loading; the practice does not benefit some users, and it can worsen rather than enhance performance in others. Recreationally active individuals, in particular, might find the supplements to be ergogenic for one exercise session but not another. Many study findings suggest that supplementation with sodium bicarbonate is most likely to improve the performance of trained athletes [ , ]. The main side effect of sodium bicarbonate supplementation in gram quantities is gastrointestinal distress, including nausea, stomach pain, diarrhea, and vomiting. Supplement users can reduce or minimize this distress by consuming the total dose in smaller amounts multiple times over an hour with fluid and a snack of carbohydrate-rich food [ , ]. Sodium bicarbonate is Such a large intake of sodium with fluid can lead to temporary hyperhydration, which could be useful in activities where large sweat losses might otherwise lead to significant fluid deficits. However, the slight increase in body weight from fluid retention might hinder performance in other sports [ ]. Studies have not evaluated the safety and effectiveness of long-term use of sodium bicarbonate as an ergogenic aid over months or longer. Many athletes find this amount of sodium bicarbonate powder dissolved in fluid to be unpalatably salty [ ]. The Australian Institute of Sport supports the use of bicarbonate for improving sports performance in suitable athletic competitions under the direction of an expert in sports medicine, but it notes that more research might be required to understand how the supplement should be used for best results [ 29 ]. The Montmorency variety of tart or sour cherry Prunus cerasus contains anthocyanins and other polyphenolic phytochemicals, such as quercetin. Researchers hypothesize that these compounds have anti-inflammatory and antioxidant effects that might facilitate exercise recovery by reducing pain and inflammation, strength loss and muscle damage from intense activity, and hyperventilation trauma from endurance activities [ ]. The labels on tart-cherry juice and concentrate products do not usually indicate that they are dietary supplements, although the labels on products containing encapsulated tart-cherry powder do. Much of the limited research on use of tart cherry to enhance exercise and athletic performance involves short-term use of a tart-cherry product or placebo by young resistance-trained men for about a week before a test of strength such as single-leg extensions or back squats ; participants continue taking the supplements for about 2 days after the test. None of the participants who drank the juice experienced airway inflammation causing upper respiratory tract symptoms after the marathon a common complaint in many marathon runners , but half of those drinking the placebo did. Another study compared a supplement containing mg freeze-dried Montmorency tart-cherry-skin powder CherryPURE with a placebo in 18 male and 9 female endurance-trained runners and triathletes age range 18—26 years [ ]. Participants took the supplements once a day for 10 days, including the day they ran a half-marathon, then for 2 days after the run. Further research is needed to determine the value of tart-cherry products for enhancing performance and recovery from intense exercise or participation in sports—especially when used on a regular basis—and the amounts of supplement, juice, or concentrate needed to provide any benefits. Studies have not identified any side effects of the fresh tart-cherry juice or concentrate or of supplements of dried tart-cherry-skin powder. However, they have not adequately assessed the safety of tart-cherry dietary supplements. There is no expert consensus on the value of taking tart-cherry products to enhance exercise and athletic performance. Tribulus terrestris common names include bindii, goat's-head, bullhead, and tackweed , is a fruit-bearing plant that is most common in Africa, Asia, Australia, and Europe. It has been used since ancient times in Greece, China, and Asia to treat low libido and infertility [ ]. Tribulus terrestris extracts contain many compounds, including steroidal saponins [ ]. Some marketers claim that Tribulus terrestris enhances exercise and athletic performance by increasing serum concentrations of testosterone and luteinizing hormone, but studies have not adequately determined its potential mechanisms of action [ ]. Only a few small, short-term clinical trials have investigated Tribulus terrestris as an ergogenic aid [ ], and none since A study in 15 resistance-trained men found no differences among those taking 3. In 22 elite male rugby players age The only toxicity studies of Tribulus terrestris were conducted in animals, where unspecified high intakes led to severe heart, liver, and kidney damage [ ]. The clinical studies described above found no side effects of Tribulus terrestris. Subsequent tests indicated hepatotoxicity, nephrotoxicity, and neurotoxicity. The man's condition improved after he discontinued the water, but the water was not tested to determine the presence or amount of Tribulus terrestris or any other potential toxin or contaminant. The Australian Institute of Sport advises against the use of Tribulus terrestris by athletes, noting that this supplement and other claimed testosterone boosters are banned from athletic competitions or have a high risk of being contaminated with substances that, if ingested, could lead to positive drug-screening results [ ]. The published biomedical literature provides no support for the efficacy and insufficient support for the safety of Tribulus terrestris for enhancing exercise performance [ ]. This section provides examples of ingredients that FDA currently prohibits in dietary supplements and that some consumers have used in the past as ergogenic aids, despite the lack of evidence supporting their use. Androstenedione is an anabolic steroid precursor, or prohormone, that the body converts to testosterone which induces muscle growth and estrogen [ ]. Major League Baseball slugger Mark McGwire popularized androstenedione as an ergogenic aid in [ ]. However, two randomized clinical trials found no performance benefits from androstenedione supplements. In one study, 10 healthy young men age 19—29 years took a single mg dose of androstenedione. The short-term or longer term use of the supplement did not affect serum testosterone concentrations, nor did it produce any significantly greater gains in resistance-training performance, muscle strength, or lean body mass. However, participants who took androstenedione for the 6 weeks experienced significant declines in their high-density lipoprotein HDL cholesterol levels and significant increases in serum estrogens. The supplements did not improve participants' muscular strength or lean body mass compared with placebo, but they significantly decreased HDL cholesterol levels and raised levels of serum estrogens. In March , FDA warned companies to cease distributing androstenedione-containing dietary supplements. The rationale was the lack of sufficient information to establish that such products could reasonably be expected to be safe and that FDA had never approved androstenedione as a new dietary ingredient permitted in supplements [ ]. Department of Justice classified androstenedione as a Schedule III controlled substance defined as a drug with a moderate to low potential for physical and psychological dependence in [ ]. The National Collegiate Athletic Association, International Olympic Committee, and World Anti-Doping Agency ban the use of androstenedione [ , ]. Dimethylamylamine DMAA is a stimulant formerly included in some preworkout and other dietary supplements claimed to enhance exercise performance and build muscle. Studies have not evaluated DMAA in humans as a potential ergogenic aid. In , FDA declared products containing this ingredient to be illegal after it received 86 reports of deaths and illnesses associated with dietary supplements containing DMAA. These reports described heart problems as well as nervous system and psychiatric disorders [ ]. Furthermore, FDA had never approved DMAA as a new dietary ingredient that would reasonably be expected to be safe [ ]. Although products marketed as dietary supplements containing DMAA are illegal in the United States, discontinued, reformulated, or even new products containing DMAA might still be found in the U. The Department of Defense's Human Performance Resource Center maintains a list of currently available products that contain DMAA or are labeled as containing DMAA, dimethylamylamine, or an equivalent chemical or marketing name e. FDA also determined that dietary supplements containing 1,3-dimethybutylamine DMBA , a stimulant chemically related to DMAA, are adulterated. As with DMAA, FDA had never approved this stimulant as a new dietary ingredient. The agency contended that there is no history of use or data offering sufficient assurance that this compound is not associated with a significant or unreasonable risk of illness or injury [ , ]. Ephedra also known as ma huang , a plant native to China, contains ephedrine alkaloids, which are stimulant compounds; the primary alkaloid is ephedrine [ ]. In the s, ephedra—frequently combined with caffeine—was a popular ingredient in dietary supplements sold to enhance exercise and athletic performance and to promote weight loss. No studies have evaluated the use of ephedra dietary supplements, with or without caffeine, as ergogenic aids. Instead, available studies have used the related synthetic compound ephedrine together with caffeine and typically measured the effects 1—2 hours after a single dose [ , ]. No data show any sustained improvement in athletic performance over time with continued dosing of ephedrine with caffeine [ ]. Ephedra use has been associated with death and serious adverse effects, including nausea, vomiting, psychiatric symptoms such as anxiety and mood change , hypertension, palpitations, stroke, seizures, and heart attack [ , ]. In , FDA banned the sale of dietary supplements containing ephedrine alkaloids in the United States because they are associated with an unreasonable risk of illness or injury [ ]. FDA regulates dietary supplements for exercise and athletic performance in accordance with the Dietary Supplement Health and Education Act of [ ]. Like other dietary supplements, exercise- and athletic-performance supplements differ from over-the-counter or prescription medications in that they do not require premarket review or approval by FDA. Supplement manufacturers are responsible for determining that their products are safe and their label claims are truthful and not misleading, although they are not required to provide this evidence to FDA before marketing their products. If FDA finds a supplement to be unsafe, it may remove the product from the market or ask the manufacturer to voluntarily recall the product. FDA and the Federal Trade Commission FTC may also take regulatory actions against manufacturers that make unsubstantiated physical-performance or other claims about their products. FDA permits dietary supplements to contain only dietary ingredients, such as vitamins, minerals, amino acids, herbs, and other botanicals. It does not permit these products to contain pharmaceutical ingredients, and manufacturers may not promote them to diagnose, treat, cure, or prevent any disease [ ]. For more information about dietary supplement regulation, see the ODS publication, Dietary Supplements: What You Need to Know. Like all dietary supplements, supplements used to enhance exercise and athletic performance can have side effects and might interact with prescription and over-the-counter medications. In some cases, the active constituents of botanical or other ingredients promoted as ergogenic aids are unknown or uncharacterized. Furthermore, many such products contain multiple ingredients that have not been adequately tested in combination with one another. People interested in taking dietary supplements to enhance their exercise and athletic performance should talk with their health care providers about the use of these products. The Uniformed Services University and the U. Anti-Doping Agency maintain a list of products marketed as dietary supplements that contain stimulants, steroids, hormone-like ingredients, controlled substances, or unapproved drugs and that can have health risks for warfighters and others who take them for bodybuilding or other forms of physical performance [ ]. FDA requires the manufacture of dietary supplements to comply with quality standards that ensure that these products contain only the labeled ingredients and amounts and are free of undeclared substances and unsafe levels of contaminants [ ]. However, FDA notes that products marketed as dietary supplements for bodybuilding are among those most often adulterated with undeclared or deceptively labeled ingredients, such as synthetic anabolic steroids or prescription medications [ ]. As one example, some products sold for bodybuilding are adulterated with selective androgen receptor modulators; these synthetic drugs are designed to mimic the effects of testosterone [ ]. Using such tainted products can cause health problems and lead to disqualification of athletes from competition if a drug test shows that they have consumed prohibited substances, even if they have done so unknowingly. FDA has warned against the use of any body-building products that claim to contain steroids or steroid-like substances [ ]. It recommends that a user contact their health care provider if they experience symptoms possibly related to these products, especially nausea, weakness, fatigue, fever, abdominal pain, chest pain, shortness of breath, jaundice yellowing of skin or whites of eyes , or brown or discolored urine. Some dietary-supplement firms have hired third-party certification companies to verify the identity and content of their supplements to enhance exercise and athletic performance, thus providing some extra, independent assurance that the products contain the labeled amounts of ingredients and are free of many banned substances and drugs. The major companies providing this certification service are NSF nsf. org through its Certified for Sport program, Informed-Choice informed-choice. org , and the Banned Substances Control Group bscg. Some ingredients in dietary supplements used to enhance exercise and athletic performance can interact with certain medications. Why Elite Community Servants Need Physical Therapy STAT Read more. Training with a CrossFit Physical Therapist Helps Avoid Common Injuries Read more. One Major Tip for Making Your Diet a Success Read more. The 7 Biggest Benefits of Physical Therapy Read more. Overtraining: 7 Symptoms and What You Can Do About It Today Read more. Shouldering the Blame for Shoulder Pain: Arthritis or Bursitis? Why There is No Such Thing as an Off Season Read more. Recovering from Spinal Surgery: What You Need to Know Read more. How to Treat the Most Common Sports-Related Shoulder Injuries Read more. The Cold Hard Facts About ACL Tear Risk Factors Read more. Improve Your Running Form with These 8 Tips Read more. How to Handle a Sports-Related Knee Injury Read more. How to Prevent Shoulder Impingement as an Overhead Athlete Read more. 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Strengthen Your Biceps With These 5 Home Workouts Read more. Why You Should Go to Physical Therapy Read more. Why True Sports Physical Therapy is Right For You Read more. Is It An Ache or Am I Injured? Groin Strains Symptoms and Treatments Read more. Are You Ready for Golf Season? How Athletes Avoid Knee Injuries When Competing, Practicing, Training or Working Out Read more. How to Relieve Lower Back Pain as an Athlete Read more. Quick Tips for Staying Motivated Read more. Relieve Muscle Soreness With These 5 Tips Read more. How Baseball Players Can Reduce Their Risk of UCL Injury Read more. Cupping Therapy Relieves Pain and Encourages Healing Read more. Physical Therapist vs Chiropractor: What's the Difference? Some Thoughts Before Football Season Read more. High School Sports Injuries Read more. Is Blood Flow Restriction Training Right for You? Staying Limber During Your Internship Read more. What Athletes Should Know About Tendinopathy In the Shoulder Read more. Meal Planning Tips for High School Athletes Read more. What are Achilles Tendon Conditions Signs and Symptoms? How to Relieve Sciatica Pain with Physical Therapy Read more. How to Deadlift and Squat without Risking Lower Back Injury Read more. Preventing the Most Common Lacrosse Injuries Read more. Graston Technique Read more. Is Stress Causing Your Lower Back Pain? Get Knee Pain Relief With These 3 Stretches Read more. Advice You Need to Train for a Marathon in Read more. Impact of Correct Posture on Sports Performance Read more. The Risks of a Sedentary Lifestyle — Enough To Get You Moving Read more. Make Your Outpatient Rehab Count Read more. Relieve Back Pain Fast In 5 Ways Read more. Is Elbow Arthritis Ruining Your Game? Dry Needling Can Accelerate Recovery for Athletes Read more. |
Physical Performance Enhancement -
Diuretics are drugs that change the body's balance of fluids and salts. They can cause the body to lose water, which can lower an athlete's weight. Diuretics also may help athletes pass drug tests that check for signs of drugs in the urine.
They dilute the urine and may hide traces of drugs. Diuretics can cause side effects when you take them at any dose — even at doses that health care providers suggest. These drugs make athletes more likely to have side effects such as:.
Nutrients are vitamins and minerals in foods that are good for you. Some people try to get more nutrients from products called supplements.
Supplements are sold in stores and online as powders or pills. One supplement that's popular with athletes is called creatine monohydrate. The body makes its own creatine too. It helps muscles release energy. Creatine supplements may help athletes gain small, short-term bursts of power.
Creatine seems to help muscles make more of an energy source called adenosine triphosphate ATP. ATP stores and moves energy in the body's cells. It's used for activity that involves quick bursts of movement, such as weightlifting or sprinting. But there's no proof that creatine helps you do better at sports that make you breathe at a higher rate and raise your heart rate, called aerobic sports.
Some athletes try to gain weight so they can get bigger in size. Creatine may help you put on weight over time. But that might be due to the extra water that creatine causes the body to hold on to. Water is drawn into muscle tissue, away from other parts of the body.
That puts you at risk of getting dehydrated. Studies show that it's safe for healthy adults to use creatine for a short or long time. It's important to use the doses that creatine makers suggest on the package. Stimulants boost the levels of some chemicals in the brain.
They also make the heart beat faster and raise blood pressure. Common stimulants include caffeine and drugs called amphetamines. Cold medicines often have a stimulant in them.
Energy drinks are popular among many athletes. They often have high doses of caffeine and other stimulants. The street drugs cocaine and methamphetamine also are stimulants. Some athletes may seem to get an edge from performance-enhancing drugs. But doping can have bad effects on health.
In general, the long-term effects of performance-enhancing drugs haven't been studied enough. And any short-term perks come with risks. Doping is banned by most sports leagues and groups too.
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By Mayo Clinic Staff. Thank you for subscribing! Sorry something went wrong with your subscription Please, try again in a couple of minutes Retry. Show references Madden CC, et al. The primary medical use of these compounds is to treat conditions such as asthma and other respiratory ailments.
Some studies have shown beta-2 agonists have performance-enhancing effects when consistently high levels are present in the blood. The primary medical use of these compounds is to treat conditions such as hypertension, kidney disease, and congestive heart failure.
Taken without medical supervision, diuretics can result in potassium depletion and possibly even death. The primary medical use of these compounds is to treat conditions such as Attention Deficit Hyperactivity Disorder ADHD , asthma, narcolepsy, and obesity.
Marijuana is classified by Congress as a Schedule 1 drug under the Controlled Substances Act CSA. This means that it has a high potential for abuse, no accepted medical use in the United States, and lacks accepted safety data for use under medical supervision.
Side effects of cannabinoid use include:. Blood doping is the practice of misusing certain techniques and substances to increase the red blood cell mass in the body. Since the red blood cells carry oxygen to the muscles, this allows the body to transport more oxygen to working muscles and therefore can increase their aerobic capacity and endurance.
The primary use of blood transfusions and synthetic oxygen carriers are for patients who have suffered massive blood loss, either during a major surgical procedure or caused by major trauma.
Erythropoietin is used in the treatment of anemia related to kidney disease. However, misuse of these substances and techniques could lead to:. In small doses narcotics have medical uses that include relieving severe pain and inducing sleep.
However, narcotic overdose is a medical emergency and can lead to respiratory depression and even death. While a sensation of euphoria and psychological stimulation are effects common to the use of narcotics, the misuse of narcotics can pose ethical questions about the handling of the substance as well as great health risks.
The primary medical use of beta-blockers is to control hypertension, cardiac arrhythmias, angina pectoris severe chest pain , migraine, and nervous or anxiety-related conditions.
The primary medical use of these compounds is to treat allergies, asthma, inflammatory conditions, and skin disorders, among other ailments.
The long-term effects of prohibited Selective Androgen Receptor Modulators, or SARMs, like Ostarine or LGD, are still largely unknown, due to the fact that SARMs have not been approved for human use. Concerningly, hormone and metabolic modulators, like GW, are often masqueraded as, or used in combination, with SARMs.
GW never made it through pre-clinical trials because it consistently caused cancer. Although the long-term effects of SARMs are still unknown, side effects may start with hair loss and acne. More serious health consequences have also been documented, including liver toxicity, as liver enzymes rise, and drops in good cholesterol, which can affect heart health.
If this stress continues, SARMs have the potential to increase the risk of heart attack and stroke. One of the most commonly abused performance-enhancing drugs, testosterone, comes with a wide range of immediate and long-term side effects.
Continued use can cause the body to stop producing hormones naturally and lead to organ enlargement, stunted growth, liver damage, and fertility issues. Moreover, natural testosterone levels may never recover, making the consequences of doping irreversible. Side effects may also be psychological, with testosterone often being connected to increased aggressiveness because it impacts the brains subcortical structures in the amygdala and the hypothalamus.
As with any anabolic steroid use, withdrawal from testosterone use may lead to depression, and even suicide. Prohibited stimulants, like methylhexanamine, that are often found in contaminated pre-workout supplements, as well as permitted stimulants, like caffeine, can both result in negative health effects if abused.
At low doses, stimulants can lead to increased perspiration, shaking, inability to focus, and sleep loss, as well as low appetite and dehydration. In higher doses, stimulants can also lead to more severe health effects, such as rapid heart rate and high blood pressure.
Abuse of some stimulants has been shown to age the cardiovascular system more aggressively than smoking. And continued stress on the heart can eventually lead to cardiac arrhythmia, stroke, and heart attack.
Blood doping, which often involves the use of prohibited erythropoietin, or EPO, increases the number of red blood cells in the body. This increase thickens the blood, making it difficult for the heart to pump.
The result is a higher risk of life-threatening diseases including stroke, heart disease, and cerebral or pulmonary embolisms. There have been multiple deaths attributed to blood doping. I raced 13 or 14 years as a professional cyclist. I was racing in Europe full-time, we had European riders on the team, we had European staff.
I had finished a stage race in Southern Spain, like a week-long stage race, and I was just like a starfish on my bed, collapsed. He was wearing this fly fishing vest and he reached into one of the pockets and he pulled out this little red, egg-shaped capsule.
And that was the moment, he handed me this capsule, that was the moment. And it showed that they had faith in me and that they thought I had a future in the sport.
Acute caffeine ingestion has been shown to alter RPE, where effort may be greater under caffeine conditions, yet it is not perceived as such [ 12 , , , ].
Others have not found changes in RPE with caffeine use [ ]. A more recent study by Green et al. The authors noted that individual responses to caffeine might explain their unexpected findings.
In the last decade, our understanding of CNS fatigue has improved. When caffeine and NECA were given together, the effects appeared to cancel each other out, and run time was similar to placebo. When the study was repeated with peripheral intraperitoneal body cavity injections instead of brain injections, there was no effect on run performance.
The authors concluded that caffeine increased running time by delaying fatigue through CNS effects, in part by blocking adenosine receptors [ ]. Caffeine also appears to enhance cognitive performance more in fatigued than well-rested subjects [ , , ]. This phenomenon is also apparent in exercise performance [ ] both in the field [ ] and in the lab [ 60 , 63 , ].
The placebo effect is a beneficial outcome that cannot be attributed to a treatment or intervention but is brought about by the belief that one has received a positive intervention. The nocebo effect is directly opposite to this in that a negative outcome occurs following the administration of an intervention or lack of an intervention e.
knowingly ingesting a placebo [ ]. For example, the nocebo may be a substance without medical effects, but which worsens the health status of the person taking it by the negative beliefs and expectations of the patient. An example of this was reported in a study [ ] where well-trained cyclists exhibited a linear dose—response relationship in experimental trials from baseline to a moderate 4.
Athletes improved as the perceived caffeine doses increased; however, a placebo was used in all interventions. Similarly, Saunders et al. Therefore, readers are encouraged to consider whether studies that have explored the effects of caffeine on exercise have examined and reported the efficacy of the blinding of the participants.
At the highest level of sports, competitors will be near their genetic potential, will have trained intensively, followed prudent recovery protocols, and will have exploited all strategies to improve their performance—the use of an ergogenic aid, when legal, safe and effective, is an alluring opportunity.
Accordingly, caffeine is one of the most prominent ergogenic aids and is used by athletes and active individuals in a wide variety of sports and activities involving aerobic endurance.
Caffeine has been shown to benefit several endurance-type sports including cycling [ 60 , , ], running [ 91 , , ] cross-country skiing [ ] and swimming [ ]. Much of the caffeine-exercise body of literature has focused on endurance-type exercise, as this is the area in which caffeine supplementation appears to be more commonly used and likely beneficial in most, but not all, athletes [ 11 , 12 , 13 ].
For example, the caffeine concentration in over twenty thousand urine samples obtained for doping control from to was measured after official national and international competitions [ , ]. A recent systematic review was carried out on randomised placebo-controlled studies investigating the effects of caffeine on endurance performance and a meta-analysis was conducted to determine the ergogenic effect of caffeine on endurance time-trial performance [ ].
Forty-six studies met the inclusion criteria and were included in the meta-analysis. Time-trial completion time showed improvements of 2. However, there was some variability in outcomes with responses to caffeine ingestion, with two studies reporting slower time-trial performance, and five studies reporting lower mean power output during the time—trial [ ].
Dozens of endurance studies are highlighted through this review is various sections, showing consistent yet wide-ranging magnitudes of benefit for endurance performance under caffeine conditions.
Strength and power development through resistance exercise is a significant component of conditioning programs for both fitness and competitive sport.
In resistance exercise, strength is most commonly assessed using 1 repetition maximum 1RM [ ], or different isometric and isokinetic strength tests [ ].
Although several studies exploring the effects of caffeine on strength performance have been published since the ISSN caffeine position stand [ 40 ], some uncertainty surrounding the benefits of caffeine in activities involving muscular endurance, strength and power remains.
Caffeine was shown to be ergogenic for muscular endurance in two meta-analyses reporting effect sizes ranging from 0.
However, others have shown that it enhances strength but not muscular endurance [ , ], and when studies have examined multiple strength-muscular endurance tasks, there were benefits across the board [ 67 , ], none at all [ 98 , ], or even impairments in muscular endurance with caffeine use [ , ].
Ingesting caffeine prior to a muscular endurance task is likely to delay muscular fatigue, but these effects are not consistent among all studies.
Three meta-analyses explored the acute effects of caffeine on strength, and all reported ergogenic effects [ , , ]. However, the effects in these meta-analyses were small, ranging from 0. Such small improvements in muscular strength likely have the greatest practical meaningfulness for athletes competing in strength-based sports, such as powerlifting and weightlifting athletes which already seem to be among the highest users of caffeine [ ].
Power output is also assessed during different protocols of intermittent-sprinting and repeated-sprints often with the Wingate cycling test as well as assessments during running [ ] or swimming repeated sprints [ ]. The data for repeated sprint and power performance using Wingate data has been mixed.
In an older study, 10 male team-sport athletes performed 18, 4-s sprints with 2-min active recovery [ ]. A more recent study examining the effects of acute caffeine ingestion on upper and lower body Wingate performance in 22 males did not report significant findings when measuring lower body mean and peak power using the Wingate test [ ].
An older study by Greer et al. One meta-analysis reported that caffeine ingestion enhances mean and peak power during the Wingate test [ ], although the effect sizes of 0. In contrast, another meta-analysis that examined the effects of caffeine on muscle power as assessed with the Wingate test for three of the studies, and repeated sprints for a maximum of s for the fourth, did not report benefits from ingestion of caffeine [ ].
An average caffeine dose of 6. A study by Lee et al. This might suggest that the rest interval between sprints may modulate the ergogenic effects of caffeine. Indeed, a recent meta-analysis that focused on the effects of caffeine on repeated-sprint performance reported that total work, best sprint, and last sprint performance was not affected by caffeine ingestion [ ].
Several studies have also shown substantial variability in outcomes. Similarly, Woolf et al. Ballistic movements such as throws and jumps are characterized by high motor unit firing rates, brief contraction times, and high rates of force development [ ]. Many studies have explored the effects of caffeine on jumping performance [ , ].
The body of evidence has indicated that caffeine supplementation increases vertical jump height during single and repeated jumps; however, the magnitude of these effects is rather modest, with effect sizes ranging from 0.
Besides jumping, several studies have explored the effects of caffeine on throwing performance. Overall, the current body of evidence indicates that caffeine supplementation may be useful for acute improvements in ballistic exercise performance in the form of jumps and throws.
However, more research is needed to explore the effects of caffeine on different throwing exercise tests, as this has been investigated only in a few studies. Generally, the primary sports-related goal of strength and power-oriented resistance training programs is to move the force-velocity curve to the right, indicating an ability of the athlete to lift greater loads at higher velocities [ ].
Several studies have explored the effects of caffeine on movement velocity and power in resistance exercise using measurement tools such as linear position transducers [ ]. These studies generally report that caffeine ingestion provides ergogenic effects of moderate to large magnitudes, with similar effects noted for both mean and peak velocity, and in upper and lower-body exercises [ 67 , , ].
Even though this area merits further research to fill gaps in the literature, the initial evidence supports caffeine as an effective ergogenic aid for enhancing velocity and power in resistance exercise. Even though caffeine ingestion may enhance performance in the laboratory, there has been a paucity of evidence to support that these improvements transfer directly to sport-specific performance.
To address this issue, several studies have also explored the effects of caffeine on sport-specific exercise tasks using sport simulation matches. Many studies conducted among athletes competing in team and individual sports, report that caffeine may enhance performance in a variety of sport tasks.
However, there are also several studies that report no effects as outlined below:. Basketball — increased jump height, but only in those with the AA version of the CYP1A2 gene [ ], increased number of free throws attempted and free throws made, increased number of total and offensive rebounds [ ], but did not improve sprint time [ ], nor dribbling speed [ ].
Volleyball — increased number of successful volleyball actions and decreased the number of imprecise actions [ , ], although caffeine did not improve physical performance in multiple sport-specific tests in professional females [ ], nor performance in volleyball competition [ ].
Football - did not improve performance for anaerobic exercise tests used at the NFL Combine [ ]. Rugby — increased the number of body impacts, running pace, and muscle power during jumping [ , ], but did not impact agility [ ]. Field hockey — increased high-intensity running and sprinting [ ], and may offset decrements in skilled performance associated with fatigue [ ].
Ice-hockey - has limited impact on sport-specific skill performance and RPE, but may enhance physicality during scrimmage [ ]. Combat sports — increased number of offensive actions and increased the number of throws [ ].
Cross-country skiing — reduced time to complete a set distance [ ] and improved time to task failure [ ]. In summary, although reviews of the literature show that caffeine ingestion is, on average , ergogenic for a wide range of sport-specific tasks, its use might not be appropriate for every athlete.
Specifically, the use of caffeine needs to be balanced with the associated side-effects and therefore experimentation is required in order to determine the individual response before assessing whether the benefits outweigh the costs for the athlete.
Athletes should gauge their physical response to caffeine during sport practice and competition in addition to monitoring mood state and potentially disrupted sleep patterns. There is a lack of research examining potential interindividual differences in strength or anaerobic power-type exercise, but this is not the case for endurance exercise.
In the myriad of studies examining caffeine on endurance performance, the benefits of caffeine do not appear to be influenced by sex, age, VO 2 max, type of sport, or the equivalent dose of caffeine [ 13 , , ].
Nevertheless, there appears to be substantial interindividual variability in response to caffeine under exercise conditions, which may be attributed to several factors outlined below. Genetic variants affect the way we absorb, metabolize, and utilize and excrete nutrients, and gene-diet interactions that affect metabolic pathways relevant to health and performance are now widely recognized [ ].
In the field of nutrigenomics, caffeine is the most widely researched compound with several randomized controlled trials investigating the modifying effects of genetic variation on exercise performance [ 75 , , , ].
Numerous studies have investigated the effect of supplemental caffeine on exercise performance, but there is considerable inter-individual variability in the magnitude of these effects [ 11 , 13 , 44 ] or in the lack of an effect [ , ], when compared to placebo.
Due to infrequent reporting of individual data it is difficult to determine the extent to which variation in responses may be occurring. The performance of some individuals is often in stark contrast to the average findings reported, which may conclude beneficial, detrimental, or no effect of caffeine on performance.
For example, Roelands et al. These inter-individual differences appear to be partly due to variations in genes such as CYP1A2 and possibly ADORA2A , which are associated with caffeine metabolism, sensitivity and response [ ].
In the general population, individuals with the AC or CC genotype slow metabolizers have an elevated risk of myocardial infarction [ ], hypertension and elevated blood pressure [ , ], and pre-diabetes [ ], with increasing caffeinated coffee consumption, whereas those with the AA genotype show no such risk.
Additionally, regular physical activity appears to attenuate the increase in blood pressure induced by caffeine ingestion, but only in individuals with the AA genotype [ ]. In that group, a 6. Among those with the CC genotype i. In those with the AC genotype there was no effect of either dose [ ].
The findings are consistent with a previous study [ ] that observed a caffeine-gene interaction indicating improved time trial cycling performance following caffeine consumption only in those with the AA genotype.
In contrast, previous studies either did not observe any impact of the CYP1A2 gene in caffeine-exercise studies [ , ], or reported benefits only in slow metabolizers [ 75 ]. There are several reasons that may explain discrepancies in study outcomes.
The effects of genotype on performance might be the most prominent during training or competition of longer duration or an accumulation of fatigue aerobic or muscular endurance [ ], where caffeine appears to provide its greatest benefits, and where the adverse effects to slow metabolizers are more likely to manifest [ , ].
Indeed, in a study of performance in elite basketball players [ ], only in those with the AA genotype caffeine improved repeated jumps which requires maintaining velocity at take-off repeatedly as an athlete fatigues throughout a game muscular endurance - even though there was no caffeine-genotype interaction effect for this outcome.
However, caffeine similarly improved performance in those with the both AA and C-genotypes during a simulated basketball game [ ]. In a cross-over design of 30 resistance-trained men, caffeine ingestion resulted in a higher number of repetitions in repeated sets of three different exercises, and for total repetitions in all resistance exercises combined, which resulted in a greater volume of work compared to placebo conditions, but only in those with the CYP1A2 AA genotype [ ].
Although more research is warranted, there is a growing body of evidence to support the role of CYP1A2 in modifying the effects of caffeine ingestion on aerobic or muscular endurance-type exercise, which helps to determine which athletes are most likely to benefit from caffeine.
The ADORA2A gene is another genetic modifier of the effects of caffeine on performance. The adenosine A 2A receptor, encoded by the ADORA2A gene, has been shown to regulate myocardial oxygen demand and increase coronary circulation by vasodilation [ , ].
The A 2A receptor is also expressed in the brain, where it has significant roles in the regulation of glutamate and dopamine release, with associated effects on insomnia and pain [ , ]. The antagonism of adenosine receptors after caffeine ingestion is modified by the ADORA2A gene, which may allow greater improvements in dopamine transmission and lead to norepinephrine and epinephrine release due to increased neuronal firing [ ] in some genotypes versus others.
Dopamine has been associated with motivation and effort in exercising individuals, and this may be the mechanism by which differences in response to caffeine are manifested [ , , ]. Currently, only one small pilot study has examined the effect of the ADORA2A gene rs on the ergogenic effects of caffeine under exercise conditions [ ].
Twelve female subjects underwent a double-blinded, crossover trial comprising two min cycling time trials following caffeine ingestion or placebo. Caffeine benefitted all six subjects with the TT genotype, but only one of the six C allele carriers.
Further studies are needed to confirm these preliminary findings and should include a large enough sample to distinguish any effects between the different C allele carriers i. CT vs. CC genotypes and potential effects related to sex.
The ADORA2A rs genotype has also been implicated, by both objective and subjective measures, in various parameters of sleep quality after caffeine ingestion in several studies [ , , , ].
Adenosine promotes sleep by binding to its receptors in the brain, mainly A 1 and A 2A receptors, and caffeine exerts an antagonist effect, blocking the receptor and reversing the effects of adenosine and promoting wakefulness [ ]. This action of caffeine may also serve athletes well under conditions of jetlag, and irregular or early training or competition schedules.
Psychomotor speed relies on the ability to respond, rapidly and reliably, to randomly occurring stimuli which is a critical component of, and characteristic of, most sports [ ].
Genetic variation in ADORA2A has been shown to be a relevant determinant of psychomotor vigilance in the rested and sleep-deprived state and modulates individual responses to caffeine after sleep deprivation [ ].
Those with the CC genotype of ADORA2A rs consistently performed on a higher level on the sustained vigilant attention task than T-allele -carriers; however, this was tested in ADORA2A haplotypes that included combinations of 8 SNPs. This work provides the basis for future genetic studies of sleep using individual ADORA2A SNPs.
As mentioned, the ADORA2A genotype has also been implicated in sleep quality and increases in sleep disturbance [ ]. Increased beta activity in nonREM sleep may characterize individuals with insomnia when compared with healthy good sleepers [ ]. A functional relationship between the ADORA2A genotype and the effect of caffeine on EEG beta activity in nonREM sleep has previously been reported [ ], where the highest rise was in individuals with the CC genotype, approximately half in the CT genotype, whereas no change was present in the TT genotype.
Consistent with this observation, the same study found individuals with the CC and TC genotypes appeared to confer greater sensitivity towards caffeine-induced sleep disturbance compared to the TT genotype [ ].
This suggests that a common variant in ADORA2A contributes to subjective and objective responses to caffeine on sleep. Given that anxiety may be normalized in elite sports even at clinical levels, factors that contribute to anxiety should be mitigated whenever possible.
Anxiety may be caused by stress-related disorders burnout , poor quality sleep patterns often related to caffeine intakes and possibly as a response to caffeine ingestion due to genetic variation, even at low levels [ ]. As previously mentioned, caffeine blocks adenosine receptors, resulting in the stimulating effects of caffeine [ ].
A common variation in the ADORA2A adenosine A 2A receptor gene contributes to the differences in subjective feelings of anxiety after caffeine ingestion [ , ], especially in those who are habitually low caffeine consumers [ ]. This may be particularly relevant to athletes who possess the TT variant of rs in the ADORA2A gene.
These individuals are likely to be more sensitive to the stimulating effects of caffeine and experience greater increases in feelings of anxiety after caffeine intake than do individuals with either the CT or CC variant [ , , ].
Sport psychologists commonly work with athletes to help them overcome anxiety about performance during competitions. Anxiety before or during athletic competitions can interfere not only in performance, but also in increased injury risk [ ]. Athletes who are more prone to performance anxiety may exacerbate their risk for feelings of anxiety depending on their caffeine use and which variant of the ADORA2A gene they possess.
Monitoring the actions of caffeine in those individuals who are susceptible, may alleviate some of the related feelings of anxiety with caffeine use. Given that anxiety may disrupt concentration and sleep and negatively impact social interactions, athletes with higher risks and prevalence for anxiety, may want to limit or avoid caffeine consumption if caffeine is a known trigger during times where they are feeling anxious or stressed, such as at sporting competitions or social gatherings or other work and school events.
The importance of both sleep and caffeine as an ergogenic aid to athletes highlights the importance of optimizing rest and recovery through a better understanding of which athletes may be at greater risk of adverse effects of caffeine on mood and sleep quality, possibly due to genetic variation.
This information will allow athletes and coaching staff to make informed decisions on when and if to use caffeine when proximity to sleep is a factor. These considerations will also be in conjunction with the possibility that an athlete will benefit from caffeine in endurance-based exercise as determined in part, by their CYP1A2 genotype, albeit with a clear need for future research.
The quantification of habitual caffeine intake is difficult, which is problematic for studies aiming to compare performance outcomes following caffeine ingestion in habitual versus non-habitual caffeine users.
This concern is highlighted by reports showing large variability in the caffeine content of commonly consumed beverages, e. Self-reported intakes may therefore be unreliable. Newly discovered biomarkers of coffee consumption may be more useful for quantifying intakes in the future, but currently, these are not widely available [ ].
Different protocols for the length of the caffeine abstinence period preceding data collection is also a relevant factor in determining variability in performance outcomes.
For example, in shorter caffeine abstinence periods e. alleviating the negative symptoms of withdrawal, which in itself may improve performance [ ].
These effects may be more pronounced in those genetically predisposed to severe withdrawal effects [ ]. Although genes have been associated with habitual caffeine intake using GWAS research [ , ], it is important to highlight that these associations are not directly applicable to determining differences in performance outcomes in response to acute caffeine doses for regular or habitual caffeine users versus non-habitual users.
Furthermore, associations between genes and habitual caffeine intake do not elucidate potential mechanisms by which caffeine intake behaviors may influence subsequent performance following caffeine supplementation [ , ].
In animal model studies, regular consumption of caffeine has been associated with an upregulation of the number of adenosine receptors in the vascular and neural tissues of the brain [ ]. Although, this did not appear to modify the effects of caffeine in one study [ ], in another, chronic caffeine ingestion by mice caused a marked reduction in locomotor exploratory activity [ ].
Changes in adenosine receptor number or activity have not been studied in humans. There does not appear to be a consistent difference in the performance effects of acute caffeine ingestion between habitual and non-habitual caffeine users, and study findings remain equivocal.
In one study, habitual stimulation from caffeine resulted in a general dampening of the epinephrine response to both caffeine and exercise; however, there was no evidence that this impacted exercise performance [ ].
Four weeks of caffeine ingestion resulted in increased tolerance to acute caffeine supplementation in previously low habitual caffeine consumers, with the ergogenic effect of acute caffeine supplementation no longer apparent [ ]. Caffeine ingestion improved performance as compared to placebo and control, with no influence of habitual caffeine intake.
However, a limitation of this study is the short h caffeine withdrawal period in all groups which may have resulted in performance improvements due to the reversal of caffeine withdrawal effects, rather than impact of acute-on-chronic caffeine administration and the effects of habituation to caffeine on exercise performance [ , ].
In addition, habitual caffeine intake was estimated using a food frequency questionnaire, which might be a limitation given the already mentioned variation of caffeine in coffee and different supplements.
There is wide variability in caffeine content of commonly consumed items, and as such, an objective measure e. Based on these observations, the assumption that habitual and nonhabitual caffeine consumers will or will not respond differently to caffeine supplementation during exercise, requires further study.
However, caffeine appears to be most beneficial during times or in sports where there is an accumulation of fatigue, i. A recent review [ ] reported that the effect size of caffeine benefits increase with the increasing duration of the time trial event, meaning that timing caffeine intake closer to a time of greater fatigue, i.
This supports the notion that endurance athletes with longer races may benefit most from caffeine for performance enhancement since they have the greatest likelihood of being fatigued. This also supports findings in other investigations that show ingesting caffeine at various time points including late in exercise may be most beneficial [ ].
For example, an early study [ ] aimed to understand whether or not there were benefits to a common practice among endurance athletes, such as those participating in marathons and triathlons, which is to drink flat cola toward the end of an event.
When researchers investigated the ingestion of a low dose of caffeine toward the end of a race e. The study also demonstrated that the effect was due to the caffeine and not the carbohydrate, which may also aid performance as fuel stores become depleted [ ].
This may have been due to the faster absorption with caffeinated gum consumption, and due to the continued increase in plasma caffeine concentrations during the cycling time trial, when athletes may become fatigued i. However, there was significant interindividual variability, highlighting the need for athletes to experiment with their own strategies as far as dosing and timing are concerned.
The optimal timing of caffeine ingestion may depend on the source of caffeine. As stated earlier, some of the alternate sources of caffeine such as caffeine chewing gums may absorb more quickly than caffeine ingested in caffeine-containing capsules [ 60 ].
Therefore, individuals interested in supplementing with caffeine should consider that timing of caffeine ingestion will likely be influenced by the source of caffeine. Currently, only a few investigations [ 96 , , , , , ] have included both trained and untrained subjects in their study design.
A limitation of this study is that the swimming exercise task differed between the trained and untrained participants. Specifically, the study utilized m swimming for the trained swimmers and m for the untrained swimmers, which is a likely explanation for these findings.
However, some have also postulated that this is because athletes perform more reliably on a given task than nonathletes, and increased test-retest reliability might prevent type II errors [ ]. In contrast to the above evidence regarding the importance of training status, other research has shown that training status does not moderate the ergogenic effects of caffeine on exercise performance.
One study [ ] showed similar performance improvements 1. Similarly, Astorino et al. More recently, a small study by Boyett et al. Subjects completed four experimental trials consisting of a 3-km cycling time trial performed in randomized order for each combination of time of day morning and evening and treatment.
They reported that both untrained and trained subjects improved performance with caffeine supplementation in the morning; however, only the untrained subjects improved when tested in the evening. Although there were some limitations to this study, these observations indicate that trained athletes are more likely to experience ergogenic effects from caffeine in the morning, while untrained individuals appear to receive larger gains from caffeine in the evening than their trained counterparts.
This may further complicate the training status data with a possible temporal effect [ ]. The concentration of adenosine receptors the primary target of caffeine do appear to be higher in trained compared to untrained individuals, but this has only been reported in animal studies [ ].
Boyett et al. Although some studies comparing training status of subjects support the notion [ ] that training influences response to caffeine during exercise, most do not [ 96 , , ] and this was also the finding in a subsequent meta-analysis [ ].
It is possible that the only difference between trained and untrained individuals is that trained individuals likely have the mental discipline to exercise long or hard enough to benefit more from the caffeine stimulus, which might provide an explanation for why in some studies, trained individuals respond better to caffeine [ ].
Currently, it seems that trained and untrained individuals experience similar improvements in performance following caffeine ingestion; however, more research in this area is warranted.
The impacts of caffeine on sleep and behavior after sleep deprivation are widely reported [ ]. Sleep is recognized as an essential component of physiological and psychological recovery from, and preparation for, high-intensity training in athletes [ , ].
Chronic mild to moderate sleep deprivation in athletes, potentially attributed to caffeine intakes, may result in negative or altered impacts on glucose metabolism, neuroendocrine function, appetite, food intake and protein synthesis, as well as attention, learning and memory [ ].
Objective sleep measures using actigraphy or carried out in laboratory conditions with EEG have shown that caffeine negatively impacts several aspects of sleep quality such as: sleep latency time to fall asleep , WASO wake time after sleep onset , sleep efficiency and duration [ ]. Studies in athletes have also shown adverse effects in sleep quality and markers for exercise recovery after a variety of doses of caffeine ingestion [ , , ].
Although caffeine is associated with sleep disturbances, caffeine has also been shown to improve vigilance and reaction time and improved physical performance after sleep deprivation [ , , , , ].
This may be beneficial for athletes or those in the military who are traveling or involved in multiday operations, or sporting events and must perform at the highest level under sleep-deprived conditions [ , , , ].
Even though caffeine ingestion may hinder sleep quality, the time of day at which caffeine is ingested will likely determine the incidence of these negative effects. For example, in one study that included a sample size of 13 participants, ingestion of caffeine in the morning hours negatively affected sleep only in one participant [ ].
Unfortunately, athletes and those in the military are unlikely to be able to make adjustments to the timing of training, competition and military exercises or the ability to be combat ready.
However, to help avoid negative effects on sleep, athletes may consider using caffeine earlier in the day whenever possible.
Pronounced individual differences have also been reported where functional genetic polymorphisms have been implicated in contributing to individual sensitivity to sleep disruption [ , ] and caffeine impacts after sleep deprivation [ ] as discussed in the Interindividual variation in response to caffeine: Genetics section of this paper.
As with any supplement, caffeine ingestion is also associated with certain side-effects. Some of the most commonly reported side-effects in the literature are tachycardia and heart palpitations, anxiety [ , ], headaches, as well as insomnia and hindered sleep quality [ , ].
For example, in one study, caffeine ingestion before an evening Super Rugby game resulted in a delay in time at sleep onset and a reduction in sleep duration on the night of the game [ ]. Caffeine ingestion is also associated with increased anxiety; therefore, its ingestion before competitions in athletes may exacerbate feelings of anxiety and negatively impact overall performance see caffeine and anxiety section.
For example, athletes competing in sports that heavily rely on the skill component e. However, athletes in sports that depend more on physical capabilities, such as strength and endurance e.
These aspects are less explored in research but certainly warrant consideration in the practical context to optimize the response to caffeine supplementation. The primary determinant in the incidence and severity of side-effects associated with caffeine ingestion is the dose used.
Side-effects with caffeine seem to increase linearly with the dose ingested [ ]. Therefore, they can be minimized—but likely not fully eliminated—by using smaller doses, as such doses are also found to be ergogenic and produce substantially fewer side-effects [ ].
In summary, an individual case-by-case basis approach is warranted when it comes to caffeine supplementation, as its potential to enhance performance benefit needs to be balanced with the side-effects risk. In addition to exercise performance, caffeine has also been studied for its contribution to athletes of all types including Special Forces operators in the military who are routinely required to undergo periods of sustained cognitive function and vigilance due to their job requirements Table 1.
Hogervorst et al. They found that caffeine in a carbohydrate-containing performance bar significantly improved both endurance performance and complex cognitive ability during and after exercise [ 82 ].
Antonio et al. This matches a IOM report [ ] that the effects of caffeine supplementation include increased attention and vigilance, complex reaction time, and problem-solving and reasoning.
One confounding factor on cognitive effects of caffeine is the role of sleep. Special Forces military athletes conduct operations where sleep deprivation is common. A series of different experiments [ 42 , , , , , , , ] have examined the effects of caffeine in real-life military conditions.
In three of the studies [ , , ], soldiers performed a series of tasks such as a 4 or 6. The investigators found that vigilance was either maintained or enhanced under the caffeine conditions vs.
placebo , in addition to improvements in run times and obstacle course completion [ , , ]. Similarly, Lieberman et al. Navy Seals. The positive effects of caffeine on cognitive function were further supported by work from Kamimori et al.
The caffeine intervention maintained psychomotor speed, improved event detection, increased the number of correct responses to stimuli, and increased response speed during logical reasoning tests.
Under similar conditions of sleep deprivation, Tikuisis et al. When subjects are not sleep deprived, the effects of caffeine on cognition appear to be less effective. For example, Share et al. In addition to the ability of caffeine to counteract the stress from sleep deprivation, it may also play a role in combatting other stressors.
Gillingham et al. However, these benefits were not observed during more complex operations [ ]. Crowe et al. Again, no cognitive benefit was observed.
Other studies [ , , , ] support the effects of caffeine on the cognitive aspects of sport performance, even though with some mixed results [ , ]. Foskett et al. This was supported by Stuart et al. firefighting, military related tasks, wheelchair basketball [ ].
The exact mechanism of how caffeine enhances cognition in relation to exercise is not fully elucidated and appears to work through both peripheral and central neural effects [ ].
In a study by Lieberman et al. Repeated acquisition are behavioral tests in which subjects are required to learn new response sequences within each experimental session [ ]. The researchers [ 42 ] speculated that caffeine exerted its effects from an increased ability to sustain concentration, as opposed to an actual effect on working memory.
Other data [ ] were in agreement that caffeine reduced reaction times via an effect on perceptual-attentional processes not motor processes. This is in direct contrast to earlier work that cited primarily a motor effect [ ]. Another study with a sugar free energy drink showed similar improvements in reaction time in the caffeinated arm; however, they attributed it to parallel changes in cortical excitability at rest, prior, and after a non-fatiguing muscle contraction [ ].
The exact cognitive mechanism s of caffeine have yet to be elucidated. Based on some of the research cited above, it appears that caffeine is an effective ergogenic aid for individuals either involved in special force military units or who may routinely undergo stress including, but not limited to, extended periods of sleep deprivation.
Caffeine in these conditions has been shown to enhance cognitive parameters of concentration and alertness. It has been shown that caffeine may also benefit sport performance via enhanced passing accuracy and agility.
However, not all of the research is in agreement. It is unlikely that caffeine would be more effective than actually sleeping, i. Physical activity and exercise in extreme environments are of great interest as major sporting events e.
Tour de France, Leadville , Badwater Ultramarathon are commonly held in extreme environmental conditions. Events that take place in the heat or at high altitudes bring additional physiological challenges i.
Nonetheless, caffeine is widely used by athletes as an ergogenic aid when exercising or performing in extreme environmental situations. Ely et al. Although caffeine may induce mild fluid loss, the majority of research has confirmed that caffeine consumption does not significantly impair hydration status, exacerbate dehydration, or jeopardize thermoregulation i.
Several trials have observed no benefit of acute caffeine ingestion on cycling and running performance in the heat Table 2 [ , , ].
It is well established that caffeine improves performance and perceived exertion during exercise at sea level [ , , , ]. Despite positive outcomes at sea level, minimal data exist on the ergogenic effects or side effects of caffeine in conditions of hypoxia, likely due to accessibility of this environment or the prohibitive costs of artificial methods.
To date, only four investigations Table 3 have examined the effects of caffeine on exercise performance under hypoxic conditions [ , , , ]. Overall, results to date appear to support the beneficial effects of caffeine supplementation that may partly reduce the negative effects of hypoxia on the perception of effort and endurance performance [ , , , ].
Sources other than commonly consumed coffee and caffeine tablets have garnered interest, including caffeinated chewing gum, mouth rinses, aerosols, inspired powders, energy bars, energy gels and chews, among others. While the pharmacokinetics [ 18 , , , , ] and effects of caffeine on performance when consumed in a traditional manner, such as coffee [ 47 , 49 , 55 , , , , ] or as a caffeine capsule with fluid [ 55 , , , ] are well understood, curiosity in alternate forms of delivery as outlined in pharmacokinetics section have emerged due to interest in the speed of delivery [ 81 ].
A recent review by Wickham and Spriet [ 5 ] provides an overview of the literature pertaining to caffeine use in exercise, in alternate forms. Therefore, here we only briefly summarize the current research. Several investigations have suggested that delivering caffeine in chewing gum form may speed the rate of caffeine delivery to the blood via absorption through the extremely vascular buccal cavity [ 58 , ].
Kamimori and colleagues [ 58 ] compared the rate of absorption and relative caffeine bioavailability from caffeinated chewing gum and caffeine in capsule form. The results suggest that the rate of drug absorption from the gum formulation was significantly faster.
These findings suggest that there may be an earlier onset of pharmacological effects from caffeine delivered through the gum formulation.
Further, while no data exist to date, it has been suggested that increasing absorption via the buccal cavity may be preferential over oral delivery if consumed closer to or during exercise, as splanchnic blood flow is often reduced [ ], potentially slowing the rate of caffeine absorption.
To date, five studies [ 59 , 60 , 61 , 62 , 63 ] have examined the potential ergogenic impact of caffeinated chewing gum on aerobic performance, commonly administered in multiple sticks Table 4. To note, all studies have been conducted using cycling interventions, with the majority conducted in well-trained cyclists.
However, more research is needed, especially in physically active and recreationally training individuals. Four studies [ 64 , 66 , 68 , ] have examined the effect of caffeinated chewing gum on more anaerobic type activities Table 4.
Specifically, Paton et al. The reduced fatigue in the caffeine trials equated to a 5. Caffeinated gum consumption also positively influenced performance in two out of three soccer-specific Yo-Yo Intermittent Recovery Test and CMJ tests used in the assessment of performance in soccer players [ 66 ].
These results suggest that caffeine chewing gums may provide ergogenic effects across a wide range of exercise tasks. To date, only Bellar et al. Future studies may consider comparing the effects of caffeine in chewing gums to caffeine ingested in capsules. Specifically, the mouth contains bitter taste sensory receptors that are sensitive to caffeine [ ].
It has been proposed that activation of these bitter taste receptors may activate neural pathways associated with information processing and reward within the brain [ , , ].
Physiologically, caffeinated mouth rinsing may also reduce gastrointestinal distress potential that may be caused when ingesting caffeine sources [ , ].
Few investigations on aerobic [ 69 , 74 , 75 , 76 , ] and anaerobic [ 72 , 73 , 78 ] changes in performance, as well as cognitive function [ 70 , 71 ] and performance [ 77 ], following CMR have been conducted to date Table 5. One study [ ] demonstrated ergogenic benefits of CMR on aerobic performance, reporting significant increases in distance covered during a min arm crank time trial performance.
With regard to anaerobic trials, other researchers [ 72 ] have also observed improved performance, where recreationally active males significantly improved their mean power output during repeated 6-s sprints after rinsing with a 1.
While CMR has demonstrated positive outcomes for cyclists, another study [ 78 ] in recreationally resistance-trained males did not report any significant differences in the total weight lifted by following a 1.
CMR appears to be ergogenic in cycling to include both longer, lower-intensity and shorter high-intensity protocols.
The findings on the topic are equivocal likely because caffeine provided in this source does not increase caffeine plasma concentration and increases in plasma concentration are likely needed to experience an ergogenic effect of caffeine [ 69 ].
Details of these studies, as well as additional studies may be found in Table 5. The use of caffeinated nasal sprays and inspired powders are also of interest.
Three mechanisms of action have been hypothesized for caffeinated nasal sprays. Firstly, the nasal mucosa is permeable, making the nasal cavity a potential route for local and systemic substance delivery; particularly for caffeine, a small molecular compound [ 11 , 12 , 30 , 31 ].
Secondly, and similar to CMR, bitter taste receptors are located in the nasal cavity. The use of a nasal spray may allow for the upregulation of brain activity associated with reward and information processing [ ]. Thirdly, but often questioned due to its unknown time-course of action, caffeine could potentially be transported directly from the nasal cavity to the CNS, specifically the cerebrospinal fluid and brain by intracellular axonal transport through two specific neural pathways, the olfactory and trigeminal [ , ].
No significant improvements were reported in either anaerobic and aerobic performance outcome measures despite the increased activity of cingulate, insular, and sensory-motor cortices [ 79 ].
Laizure et al. Both were found to have similar bioavailability and comparable plasma concentrations with no differences in heart rate or blood pressure Table 6. While caffeinated gels are frequently consumed by runners, cyclists and triathletes, plasma caffeine concentration studies have yet to be conducted and only three experimental trials have been reported.
Cooper et al. In the study by Cooper et al. In contrast, Scott et al. utilized a shorter time period from consumption to the start of the exercise i. However, these ideas are based on results from independent studies and therefore, future studies may consider exploring the optimal timing of caffeine gel ingestion in the same group of participants.
More details on these studies may be found in Table 7. Similar to caffeinated gels, no studies measured plasma caffeine concentration following caffeinated bar consumption; however, absorption and delivery likely mimic that of coffee or caffeine anhydrous capsule consumption.
While caffeinated bars are commonly found in the market, research on caffeinated bars is scarce. To date, only one study [ 82 ] Table 7 has examined the effects of a caffeine bar on exercise performance. Furthermore, cyclists significantly performed better on complex information processing tests following the time trial to exhaustion after caffeine bar consumption when compared to the carbohydrate only trial.
As there is not much data to draw from, future work on this source of caffeine is needed. A review by Trexler and Smith-Ryan comprehensively details research on caffeine and creatine co-ingestion [ 32 ].
With evidence to support the ergogenic benefits of both creatine and caffeine supplementation on human performance—via independent mechanisms—interest in concurrent ingestion is of great relevance for many athletes and exercising individuals [ 32 ].
While creatine and caffeine exist as independent supplements, a myriad of multi-ingredient supplements e. It has been reported that the often-positive ergogenic effect of acute caffeine ingestion prior to exercise is unaffected by creatine when a prior creatine loading protocol had been completed by participants [ , ].
However, there is some ambiguity with regard to the co-ingestion of caffeine during a creatine-loading phase e. While favorable data exist on muscular performance outcomes and adaptations in individuals utilizing multi-ingredient supplements e. Until future investigations are available, it may be prudent to consume caffeine and creatine separately, or avoid high caffeine intakes when utilizing creatine for muscular benefits [ ].
This is likely due to the heterogeneity of experimental protocols that have been implemented and examined. Nonetheless, a systematic review and meta-analysis of 21 investigations [ ] concluded the co-ingestion of carbohydrate and caffeine significantly improved endurance performance when compared to carbohydrate alone.
However, it should be noted that the magnitude of the performance benefit that caffeine provides is less when added to carbohydrate i. carbohydrate than when isolated caffeine ingestion is compared to placebo [ ]. Since the publication [ ], results remain inconclusive, as investigations related to sport-type performance measures [ 83 , , , , , , ], as well as endurance performance [ 84 , , ] continue to be published.
Overall, to date it appears caffeine alone, or in conjunction with carbohydrate is a superior choice for improving performance, when compared to carbohydrate supplementation alone.
Few studies to date have investigated the effect of post-exercise caffeine consumption on glucose metabolism [ , ]. While the delivery of exogenous carbohydrate can increase muscle glycogen alone, Pedersen et al.
In addition, it has been demonstrated that co-ingestion of caffeine with carbohydrate after exercise improved subsequent high-intensity interval-running capacity compared with ingestion of carbohydrate alone.
This effect may be due to a high rate of post-exercise muscle glycogen resynthesis [ ]. Practically, caffeine ingestion in close proximity to sleep, coupled with the necessity to speed glycogen resynthesis, should be taken into consideration, as caffeine before bed may cause sleep disturbances.
The genus of coffee is Coffea , with the two most common species Coffea arabica arabica coffee and Coffea canephora robusta coffee used for global coffee production.
While coffee is commonly ingested by exercising individuals as part of their habitual diet, coffee is also commonly consumed pre-exercise to improve energy levels, mood, and exercise performance [ 11 , 40 ]. Indeed, a recent review on coffee and endurance performance, reported that that coffee providing between 3 and 8.
Specifically, Higgins et al. Since the release of the Higgins et al.
Don't put the cart before the horse Physical Performance Enhancement Body composition for beginners your athletes to max Psrformance when they don't possess the tools. Often we Physical Performance Enhancement players forced Phyaical compete Physical Performance Enhancement a high performance level in their sport often getting beat by talent alone. When forced to compete on talent alone - the better talent always wins. To close the gap, athletes are typically forced into even more performance activities. This could increase the problem by putting skill sets before building strength and conditioning.
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