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From 2 to 6 blocks: Which body composition model is best for you?
In the field of fitness, the quantification of body composition refers to the description of the different components of the human body, which may include fat, bone, water, and muscle. Even if two people are the same gender, height, and weight, their body types can be very different because of differences in body composition. This can be explained by factors such as the amount of fat mass, the density of muscles, or the size of bones.
Body composition model
Body composition models typically use 2 to 6 blocks to describe the human body. Here are some common models:
2 block model: fat mass (FM) and fat-free mass (FFM)
3 block model: fat mass (FM), moisture and fat-free dry mass
4 block model: fat mass (FM), water, protein and minerals
5 block model: fat mass (FM), water, protein, bone mineral content and non-bone mineral content
6 block model: fat mass (FM), water, protein, bone mineral content, non-bone mineral content and glycogen
The sum of these blocks must equal the total weight of the human body. The proportion of each block is usually reported as a percentage and is calculated by dividing the weight of the block by the weight of the body. Individual blocks can be estimated from population averages or obtained from direct or indirect measurements. Generally, high-block models are more accurate because they require more data to account for inter-individual variability, while the four-block model is considered the reference model for body composition assessment because it accounts for most of the variability. It is robust and its components can be measured directly.
Measurement method
There are currently many methods of measuring body composition. For the four-block model, gold standard measurement techniques include body weight measurement, body density measurement using underwater weighing or air displacement volume measurement, total water volume calculated using isotope dilution analysis, and mineralogy by dual-energy X-ray absorptiometry (DEXA). Substance content measurement.
However, the practice of using only DEXA scans for body composition measurements is also growing in popularity and is known as the "gold standard." The accuracy of these claims has sometimes been questioned because measurement methods vary widely across studies.
In practice, the measurement methods used are often a trade-off between cost, availability and accuracy.
DEXA
Dual-energy X-ray absorptiometry (DEXA) is increasingly popular for clinical and research applications. DEXA scans require medical supervision by a radiologist. Whole-body scans using DEXA can accurately and precisely measure body composition, including bone mineral content (BMC), bone density (BMD), lean tissue mass, adipose tissue mass, and the fractional contribution of fat.
DEXA measurements are highly repeatable when using the same type of device and can be used to monitor programs such as drug therapy, diet or exercise interventions.
The DEXA test is fast, easy and painless, and the radiation dose to the subject is less than a cross-country flight. However, Wang et al. questioned the role of DEXA in clinical evaluation and research, pointing out that "the error of the DEXA method is still worrying, and it is not reliable enough if used as a benchmark."
Other measurement methods
In addition to DEXA, there are several other ways to measure body composition. Among them, underwater weighing is a technology directly applied using Archimedes' principle. Another option is air displacement volume measurement, which is a method of measuring body volume using air instead of water. Other methods such as isotope dilution method and bioelectrical impedance analysis are used in different occasions.
Sport Type
An individual's ideal body fat percentage depends on gender, age and physical activity. For example, a thirty-year-old woman's ideal fat percentage will be different than a man of the same age. Athletes and non-athletes also have different ideals. Fat mass can be effectively reduced through aerobic exercise and high-intensity interval training (HIIT), while resistance training can help reduce fat and increase muscle mass at the same time. It should be noted that when performing resistance training, the movements of different limbs should be separated to avoid injuries caused by repeated movements.
With different body composition models, it is sometimes difficult to choose the method that best suits you. Which model do you want to use to understand your body?
