Body Composition Assessment: Strictly speaking, body composition should include the weight of muscle, bone, fluids and blood, and fat in the body. However, the most obvious factor affecting health is fat, so the purpose of the usual body composition test is to measure The difference between body weight and lean body mass, so as to understand the weight of the subject’s body fat. There are many ways of body composition measurements, which are described below.
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Underwater weighing method for body composition measurement:
The most accurate test method is underwater weighing. Because the specific gravity of fat and non-fat components in the body is different, the buoyancy in water is different. Therefore, it is believed that the weight of the body directly immersed in water is less than the weight measured under normal conditions. This difference is caused by the difference in the specific gravity of fat, so it can be used to calculate body fat weight.
The underwater weighing method is the most commonly used method for measuring body composition. The purpose of this method is to measure the density of the human body. The density of human body fat is about 0.9 and the non-fat content is 1.10. Knowing the body density can calculate the difference between fat and body weight. The percentage of lean body mass, the density of the body is calculated from weight and volume.
The measurement method of body composition measurement volume adopts the underwater weighing method. According to Archimedes’ principle, the body density of a person can be calculated by measuring the subject’s body weight and underwater body weight.
However, the volume obtained by this method is the surface volume, so it is necessary to measure the residual air volume in the lungs for supplementary correction, and subtract the residual air volume from the surface area to calculate the volume.
Bioelectrical impedance method for body composition measurement:
The bioelectrical impedance method is to pass a safe current to the subject’s body and observe the current from the wrist to the ankle. Since the non-adipose component (more water content) in human tissue has a smaller electrical impedance than adipose tissue, when an alternating current is applied to the human body, the current will mainly pass through the non-adipose tissue. Therefore, a person with a high fat content has a slower rate of current passing through his body than a person with a low fat content.
At present, many medical device manufacturers at home and abroad have produced various types of resistive antibody composition analyzers, which can measure the body weight and fat weight percentage, muscle weight percentage, bone weight percentage and body fluid weight percentage.
The findings of the American College of Sports Medicine show that there are five main factors that affect body composition: age, gender, height, weight, and resistance. Therefore, if the measured data of bioelectrical impedance and the statistical values of the other four factors are considered together, a more accurate reference value of body composition can be obtained.
The current popular “Bioelectrical Impedance Tester” has taken all these factors into consideration, and built-in relevant software to provide testers with the most reliable test reliability and validity.
Body mass index methods of body composition measurements:
From a statistical point of view, people use the height/body mass index (bmi) to evaluate whether a person is overweight or not. bmi = weight (kg) / height 2 (m). The normal range should be 19-25, the higher the value, the higher the degree of obesity.
According to the standards of the American College of Sports Medicine, when a person’s height/body mass index exceeds 25, they are overweight, and if they exceed 30, they are obese. The standard in China is slightly lower. It is generally believed that over 23 is considered overweight, and over 28 is considered obese. The bmi method is not suitable for evaluating athletes or people with relatively developed muscles. For example, a shot put player’s muscle mass may account for a much higher proportion of body weight than the average person. If evaluated by the BMI method, his BMI index may exceed 30, but he is not obese.
Measurement of sebum thickness for body composition measurement:
This measurement is based on the assumption that 50% of the body’s fat is found under the skin. When measuring, measure the fat thickness of special parts of the body, and then use statistical formulas to calculate to obtain the percentage of body fat.
