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HOW TO ACCURATELY MEASURE BODY FAT PERCENTAGE Accu-Measure Body Fat Calipers Review Does it WORK?BIA impedance measurement technique -
Bluetooth was used for data transfer between body fat analyzer and a personal computer, and external flash memory was used for user data storage.
Contact resistance compensation function was adapted to our bioelectrical impedance analyzer. The contact resistance compensation circuit included two analog switches. One analog switch was connected between the current and voltage path of the finger electrodes, and the other was connected between the current and voltage path of the wrist electrodes.
For the 4-point measurement mode, analog switches were turned off, and for the 2-point measurement mode, analog switches were turned on for electrical connection of each voltage and current electrode pair. This very simple and small compensation circuit had a flexibility that allowed easy adaptation to variable AFEs.
The dynamic range the range of measureable impedance was configured to cover the range of body impedance and contact resistance. TX dynamic range the range of impedance that current source can drive and RX dynamic range the range of impedance that voltmeter can measure should satisfy the overall system dynamic range required.
Figure 4 b,c show the current paths for the 4-point and 2-point measurement modes, respectively. Based on our user data from volunteers in , TX and RX dynamic range were set as 15 kΩ and 10 kΩ, respectively, by adjusting the driving current level To improve measurement accuracy along the wide dynamic range stated above, a calibration algorithm that adopts 4-point coordinate conversion is proposed, in which four high-precision reference resistors are used to reduce the errors in three resistance sections.
The ADC output code was converted to impedance by calibration process. The ADC output code and body impedance Z body have a nonlinear relationship due to the finite input impedance of the voltmeter Z i and the finite output impedance of the current source R s , since the equivalent impedance detected by the voltmeter is the parallel combination impedance of body impedance Z body , Z i , and R s as in Eq.
Note that contact resistance R c is zero during the calibration process. In the calibration curve, the measurement on the x-axis is changed from reference impedance to parallel combination impedance of reference impedance, Z i , and R s.
This change enhances the linearity of the calibration curve and the accuracy of measurement. The dashed lines are ideal calibration curves, and the solid lines are extracted calibration curves derived by calibration process.
It is easily seen from Fig. Calibration algorithm was developed using C code and loaded as firmware of the device. Whenever the device is turned on, self-calibration is conducted using 4 reference resistance values as shown in Fig. Calibration curve and measurement error at midpoint between two reference points for a 2-point calibration, b 4-point calibration, and c 4-point coordinate conversion calibration.
ADC analog-to-digital converter, Z i input impedance of the voltmeter, R s output impedance of the current source. Figure 6 shows the measurement procedure and corresponding graphical user interface of our wrist-wearable device. On the home screen, a user can register information gender, age, height, and weight by touching the [CHG INFO] icon.
If the user is already registered on the device, registration process can be skipped by touching [USER] icon. The measurement is initiated by touching the [START] icon.
When the proper posture is maintained, BIA measurement begins automatically. It takes about 7 s to complete the test: 3 s for 4-point measurement, 1 s for measurement mode change, and 3 s for 2-point measurement.
When the measurement is completed, percentage body fat, lean mass, and basal metabolic rate are shown on the screen. Measurement procedure and corresponding graphical user interface of the wrist-wearable bioelectrical impedance analyzer. To evaluate the accuracy of our bioelectrical impedance analyzer, a clinical test was conducted on volunteers who were recruited at Seoul St.
Participants were recruited to have as uniform distributions as possible on the bases of gender, age, and body mass index BMI. The BIA pretesting client guidelines 20 in Table 2 were explained to all volunteers before the clinical test.
Four different devices were used in the clinical test: our wrist-wearable device, a whole-body composition analyzer InBody , an upper-body portable body fat analyzer Omron HBF , and a DEXA instrument GE Lunar Prodigy.
The study was approved by the Institutional Review Board of Seoul St. For the approval of the review board, our bioelectrical impedance analyzer was registered as a broadcasting and communication equipment MSIP-REM-SEC-SAIT-MyLean by the Ministry of Science, ICT and Future Planning MSIP , Republic of Korea.
Written informed consent was obtained from each volunteer before the clinical test. To undergo the test, participants changed into a light gown in order to control the weight of clothes. All metal items were removed from the participants to ensure accuracy of measurement. Then anthropometric measurement was conducted by a skilled nurse.
After anthropometric measurement, body impedance and body composition data were measured using the whole-body composition analyzer and the upper-body portable body fat analyzer.
Next, the DEXA instrument was used to measure the reference body composition. Finally, our wrist-wearable device was used to measure body impedance. Statistical analysis was performed after data acquisition.
The accuracy of each device was compared to that of others. Our study explored a novel method that uses considerably small electrodes that can be adapted into small devices, such as a wristwatch. Figure 7 shows the calculated contact resistance distribution of the study participants.
While the average value was Ω, it is notable that the maximum value was as high as Ω. Figure 8 a shows the impedance correlation between our device and the whole-body composition analyzer. The coefficient of determination R 2 of impedance was 0.
This result shows that there is a strong correlation for impedance measurements between the wrist-wearable bioelectrical impedance analyzer and the whole-body bioelectrical impedance analyzer, and the proposed contact resistance compensation method improves the correlation coefficient effectively.
a Impedance correlation with contact resistance compensation blue dots and without contact resistance compensation orange dots. DEXA dual-energy X-ray absorptiometry. Figure 8 b shows the correlation of percentage body fat measurement between our wrist-wearable bioelectrical impedance analyzer and the reference instrument DEXA , from which it can be seen that R is 0.
The SEE was estimated to be 3. It can be seen that the errors between the two instruments are randomly distributed without any skewed tendency and Table 3 shows the comparison of accuracy in measurement of percentage body fat by the whole-body composition analyzer, the upper-body portable body fat analyzer, and our wrist-wearable bioelectrical impedance analyzer.
We developed a novel wrist-wearable bioelectrical impedance analyzer with a contact resistance compensation function such that bioelectrical impedance can be accurately estimated even with considerably small sizes of electrodes outer electrodes: 68 mm 2 ; inner electrodes: mm 2.
The correlation coefficient and the SEE of percentage body fat relative to the DEXA instrument were estimated to be 0. Considering that the measurement time of our wrist-wearable BIA device was only 7 s and could be reduced further, this sensor technology provides a new possibility for a wearable bioelectrical impedance analyzer with more miniature electrodes toward daily obesity management.
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Healthcare Sensor Lab, Device Research Center, Samsung Advanced Institute of Technology, Samsung Electronics Co. GI Innovation, Inc. Samsung Strategy and Innovation Center, Samsung, Inc. You can also search for this author in PubMed Google Scholar. and J. Correspondence to Kak Namkoong.
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nature scientific reports articles article. Download PDF. When an electrical current is sent through your body, components such as body water, fat, muscle, and bone present varying levels of resistance. Body water is highly conductive and makes up a significant percentage of your body.
Therefore, the greater the amount of body water, the less resistance there is. For example, your muscles contain a high percentage of water , resulting in less resistance. Body fat, on the other hand, contains very little water and presents much higher resistance compared to muscle mass or body water.
To better illustrate this concept, imagine the flow of cars in traffic. The cars on the highway represent the current, and the number of lanes on the highway represents the amount of water in the body.
A highway with more lanes allows for the cars to go faster, resembling the case where there is more water or muscle mass, and the current can flow more easily.
If we close several lanes in the highway or have less water , the same number of cars will take longer to move through the highway higher resistance. The difference in the resistance to the electrical current between water, muscle, and fat cells is known as reactance.
Impedance is the vector sum of resistance and reactance. It is what BIA devices uses to determine your body composition and is measured in ohms Ω. BIA defines the human body as a cylinder and uses two mathematical concepts to describe the relationship between impedance and body water :.
Using the impedance and length of the cylinder or height of the individual , BIA can determine the volume of total body water. From there, body composition is determined , including muscle mass and body fat percentage. Now that you understand how bioelectrical impedance analysis BIA works, keep scrolling to learn how BIA technology has evolved through the years.
In , Hoffer et al. carried out a series of experiments to prove that total body water and bioelectrical impedance were highly correlated, suggesting that impedance measurements could be used for determining total body water. Impedance of the right half of the body was measured, including the right arm, torso, and right leg.
This correlation was more in agreement with the gold standard technique when compared to other indices, including body weight. The equation Hoffer et al. In , RJL Systems commercialized the impedance meter for the first time and the BIA method began to gain popularity. The device measured impedance by attaching electrodes to the back of the right hand and on top of the right foot.
Prior to this, body composition could only be measured by caliper or underwater weighing. Such methods needed to be carried out by skilled technicians, were uncomfortable, required complicated installation or use of equations, and could not accommodate a wide variety of populations.
Alternatively, BIA was easy, fast, less expensive, and non-invasive. Therefore, many body composition researchers, nutritionists, and medical experts began to use BIA. Studies proved BIA measures had high correlations with gold standard methods, such as underwater weighing and DEXA.
However, technical limitations of BIA began to surface in the late s. Two primary limitations of BIA were its assumption of the human body as a single cylinder and its use of a single frequency 50 kHz. This technique may have worked for users with standard body types, but it was not as accurate for other populations that might not fit a conventional mold, such as fit elderly adults and most medical patients.
To increase the accuracy of results, researchers derived various population-specific equations for determining body composition.
These equations were based on what is known as empirical data. Empirical data is knowledge acquired by means of observation or experimentation.
By collecting data from a sample population deemed to represent the expected characteristics of the entire population, researchers can derive equations that may be used to predict outcomes.
In body composition, researchers have identified trends in muscle and fat mass and have used this data to predict body composition based on specific variables.
In , research was published in which the impedance index was combined with factors such as body weight and gender into empirical equations. Over time, numerous other equations were developed based on additional factors such as age, ethnicity, and body type. For instance, age is a common factor in empirical equations used for body composition.
In general, most individuals tend to lose lean body mass with age due to a sedentary lifestyle. Based on this trend, empirical equations often skew lean body mass up for younger individuals and down for older individuals.
However, such data manipulation can cause inaccuracies and significant misassessments regarding health risks in population outliers such as obese youth or fit older adults. Suppose a device that relies on empirical equations to estimate body composition is used on two people who have the same amount of lean body mass, but one person is 30 years old and the other is 40 years old.
In the late s, Japanese manufacturers released various types of BIA body composition devices for general public use. Gradually, BIA devices became more popular for personal use rather than professional medical assessments due to technological constraints mentioned in the previous section. Some devices measured the impedance between both feet as the user stands on the scale, while others measured the impedance between both hands while holding the device.
In , Dr. Robert Kushner proposed that the technical limitations of BIA could be improved by measuring the human body as five separate cylinders right arm, left arm, torso, right leg, left leg instead of one. Each of these cylinders have different lengths and cross sectional areas, resulting in varying impedance values.
When considering the single cylinder model, the thinness and smaller cross-sectional area of the limbs reduce their impact on whole body impedance.
According to Kushner, measuring segmental impedance alone would not be sufficient; instead, all five body cylinders would also need to be measured at different frequencies to distinguish intracellular, extracellular and total body water. This distinction would allow for a better understanding of fluid distribution, providing an accurate measure of the hydrated state of lean mass.
In other words, the technical limitations of BIA could be overcome by measuring the different body segments at different frequencies. By doing so, the impedance in the limbs and torso were measured separately, yielding highly accurate results without using empirical data based on factors like age, gender, ethnicity, athleticism, and body shape.
Thus, the InBody DSM-MFBIA body composition analyzer is a precision medical device. Many BIA products today provide segmental measures of muscle and fat mass, but most of these products are still unable to take segmental impedance measurements, particularly in the torso.
The InBody measure each segment separately and shows the impedance values of all five cylinders of the body at each frequency in the Impedance Section of the InBody Result Sheet. InBody uses multiple currents at varying frequencies to provide precise body water analysis.
When measuring impedance with electrodes, contact resistance occurs. InBody accounts for contact resistance with strategically placed electrodes to ensure that measurements are accurate and reproducible. InBody measures your impedance independently, so your results are not affected by your age, gender, ethnicity, athleticism, or body shape.
BIA Tech Problem The ability to distinguish between extracellular and total body water is important to identify fluid imbalances related to acute inflammation or edema.
Many BIA devices use only one frequency at 50 kHz to measure impedance. As a result, patients with increased extracellular water may be misidentified as being healthy.
InBody uses a combination of low and high frequencies to determine extracellular, intracellular, and total body water. The use of multiple frequencies allows InBody devices to achieve a high level of precision.
Medical practitioners can use InBody for measurements of body composition and fluid status. Total body water TBW is stored throughout the body and can be separated into 2 compartments:.
Early BIA devices used a single 50 kHz frequency to calculate TBW. Therefore, ICW was estimated proportionally based on the ECW. This estimation was used to determine TBW, lean mass, and fat mass. The estimation of intracellular water was based on the assumption that the ratio of ICW to ECW in healthy adults is about However, individuals with body compositions that differ from conventionally healthy adults, such as elderly, obese or chronic disease patients, often have a higher ratio of ECW.
Thus, in these patient populations, relying on the ICW:ECW ratio could result in significant error. InBody uses multiple frequencies ranging from 1 kHz to 1 MHz to provide precision body water analysis.
Electrical currents interact differently with the cells at different frequencies, which allows the InBody to quantify the different fluid compartments. Low frequencies are better suited for measuring ECW, while high frequencies can pass through cell membranes to measure ICW and therefore TBW.
An accurate measure of TBW and the ability to analyze ICW versus ECW allows for a deeper analysis of individual body composition. Compartmental water measures can be used to properly quantify and identify changes in fluid balance to reflect nutritional status and fitness progress.
If the starting measurement position changes, the length of the measured cylinder also changes. This directly impacts impedance and introduces error. When the human body comes in contact with an electrode, resistance occurs. To accurately measure the resistance in the human body, it is important to control the measurement location.
These designs can cause measurements to start in the palm, which has a high impedance and can cause inaccuracies, or lead to inconsistent measurement starting points, reducing the reliability of results.
The anatomical design of the hand electrode creates a simple holding position that is easy to reproduce. Utilizing the anatomical characteristics of the human body, when an InBody user grasps the hand grip, current flows from the palm electrode and the electrical energy, or voltage, is initiated at the thumb electrode.
When current and voltage overlap, impedance can be measured. By separating current and voltage into the hand and foot electrodes, the point of overlap can be controlled to isolate the five cylinders of the body limbs and torso and consistently start at the same location on the wrists and ankles for reproducible results.
Measuement Outdoor Adventure Activities General » InBody Technology -old. Bioelectrical impedance analysis BIA is a measurememt Skin and hair health to measure the components of the bodyincluding muscle mass, Sports nutrition for the elderly fat, techhnique total iimpedance water. Measuremen low and high- frequency electrical currents are sent through the water in measuremenh body via Skin and hair health jmpedance electrodes to measure tecchnique. The impedance is used to determine total body water TBWwhich can then be used to derive your fat-free mass—the portion of your body that does not contain fat, including your muscle and bone—and then body fat. How Bioelectrical Impedance Analysis BIA Works To understand how bioelectrical impedance analysis works, it is important to understand the core concepts of resistance and reactance and how they are used to calculate impedance. When an electrical current is sent through your body, components such as body water, fat, muscle, and bone present varying levels of resistance. Body water is highly conductive and makes up a significant percentage of your body. Use a BIA Scale to Meet Fitness and Weight Loss Goals. Outdoor Adventure Activities BIIA, MD, is a Boost metabolism naturally internist, measuremment cardiologist, and fellow of the American BIA impedance measurement technique impexance Cardiology. Adah is an occupational techniqe, Outdoor Adventure Activities in the area of pediatrics with elementary students with special needs in the schools. Her work as an occupational therapist includes: home health, acute care, chronic care, seating and positioning, outpatient rehab, and skilled nursing rehab. Bioelectrical impedance analysis BIA measures body composition based on the rate at which an electrical current travels through the body. Body fat adipose tissue causes greater resistance impedance than lean mass and slows the rate at which the current travels.
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