How is the fat content of NBA players measured?

The following are several international fat content measurement methods.

1. Underwater weighing method (underwater weighing)

It is a method to calculate the weight of body fat by measuring the water displacement, lean body mass density and adipose tissue density of human body, and then calculate the percentage of body fat content. This method has small error and high precision, but it needs special test space and tools and has many operation steps. It is only suitable for laboratory testing and not suitable for public self-testing. The principle of underwater weighing method is also very simple: the specific gravity of human body fat is about 0.8 kg/L, and the average specific gravity of other tissues except fat is about1.0 kg/L. By weighing the weight of human body in air, the weight when it is filled with air in water and the weight after it is exhausted in water, the total weight of human body fat can be obtained by simple calculation.

2. Sebum forceps measuring caliper (anthropometry-skin wrinkle measurement)

It is a method to calculate the percentage of body fat by measuring the thickness of subcutaneous fat at multiple points. This method is closely related to the human model used in the calculation process. The data of European and American mannequins can't be used in Asia, and Japanese models can't calculate the data of China people well. This method has been widely used in many countries in recent decades because of its simple operation and almost no need for space.

3. Dual energy X-ray absorption method (DEXA).

It is a method to measure the body fat content by using the principle that different tissues (minerals, lean meat and fat) have different absorption rates of X-rays. In the test, two low radiation sources detect synchronously in small steps. This method is a relatively new method with high accuracy, but the test cost is expensive and the test time is long (10-20 minutes/person). Can only be used in advanced laboratories, not outside the experiment.

4. Near-infrared interaction

It is a method to measure the fat content of human body by using the principle that near infrared rays have different degrees of penetration and reflection on different tissues of human body. The measurement of biceps brachii is often used as the main test site, and the percentage of body fat content can be calculated by substituting the test data into the equation including height, weight, body shape and activity level. This method has been widely used outside the laboratory because of its cheap instruments and simple measurement steps. However, because the pressure of the probe on the body tissue is different every time, the measurement data of the same subject are often different, so the test accuracy of this method is poor.

5. Magnetic resonance imaging (MRI)

Based on X-ray, it is a method to measure the fat content of human body by using the characteristics that human tissue cells are "excited" in different degrees under the action of magnetic field. A measurement takes about 30 minutes, and the measuring equipment is expensive. Although the measurement accuracy is high, this method is only suitable for advanced laboratories.

6. Total Body Conductivity (Tobec) for thin body conductivity measurement.

It is a method to measure lean body weight, and its principle is that human (non-fat) lean body is a good conductor. Although this method has high precision, the test time is only 10 second, but the application scope is limited to advanced laboratories because of the expensive test instruments.

7. Computed tomography [X-ray].

The X-ray tube in CT produces a beam of X-rays around the human body, which is received by the probe and generates the cross-sectional information of the human body. The computer uses complex algorithms to construct the tissue image in the human body. The equipment of this method is expensive, and the human body is exposed to radiation, so this method is limited to laboratory application.

8. Exhaust measurement method BOD POD (exhaust volume)

The measuring principle of this method is similar to the underwater weighing method. It is a method to calculate the body density by using the volume of air discharged from human body, and then calculate the fat content and ratio. During the 20 seconds required for the test, the tester sits in a sealed cabin, and the amount of air discharged is measured by a sensor connected to a computer. This method requires expensive equipment and is not convenient to carry out outside the laboratory.

9. Bioresistance measurement method BIA (bioelectrical impedance)

It uses the characteristics that thin tissue of human body is a good conductor and fat is an insulator, discharges current to human body through different electrodes, then measures human body resistance, and then substitutes the test results into the equation including height, weight, sex and age to calculate the fat content and proportion of human body.