Body composition, or the proportion of bone, muscle, tissue, and water in the body, is an important factor for athletes to consider. It can impact athletic performance, injury risk, and overall health. In this article, we will explore some of the different methods used to measure body composition and their advantages and limitations.
What is Body Composition?
At its most basic level, body composition is measured using a ‘two-compartment model’ that assesses fat mass (FM) and fat-free mass (FFM), which includes all body components except for fat. The more compartments that are measured, the less error there is in body composition estimates, but this also requires multiple methods of body composition assessment to be used.
Why Measure Body Composition?
Athletes may have their body composition assessed for a variety of reasons, including to determine the effectiveness of an intervention, track body composition goals, assess injury risk, aid in setting body composition goals, and assess health risk due to being underweight or overweight. The reasons for measurement require different levels of accuracy, with some requiring reliable results and others requiring accurate absolute numbers.
Methods of Body Composition Measurement
There are several techniques used to measure body composition, each with varying degrees of accuracy, reliability, and cost. Commonly used methods only provide an estimate of body composition because they are based on assumptions regarding the compartments measured. Here are a few of the most commonly used methods:
- Dual Energy X-Ray Absorptiometry (DXA): DXA measures body composition using two low-energy x-rays that are absorbed differently by bone and tissues. This method can measure regional body composition and bone density. However, it relies on certain assumptions that can lead to errors in measurements.
- Bioelectrical Impedance Analysis (BIA): BIA measures the impedance (resistance) of a small electrical current passed through the body, with muscle tissue containing a higher water content than fat tissue. This method only measures total body water and requires the assumption that 73% of FFM is water. However, if multiple frequency scales are used, extracellular and intracellular water can be differentiated.
- ISAK Skinfold Measurements: The skinfold technique measures subcutaneous fat thickness at various sites across the body. This method is measured in mm and converted to body fat percentage using population-specific equations. It is important to note that this is only an estimate and can be influenced by hydration status.
- Air Displacement Plethysmography (Bodpod): This method measures body composition by measuring the volume of air a person displaces within an enclosed chamber. Volume, in addition to body weight, can then be used to calculate body density, which allows FM and FFM to be estimated.
- Hydrodensitometry (Underwater Weighing): This technique involves being fully submerged in a tank of water and expelling all air in the lungs while underwater weight is measured. Body density is calculated using underwater weight and body volume, which allows FM and FFM to be estimated.
Conclusion
Body composition analysis is an important aspect of sports performance, injury risk assessment, and overall health. While no method is perfect, understanding the advantages and limitations of each method can help athletes and coaches determine the most appropriate method for their needs.
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Science References
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- Martinez-Ferran M, Rafei E, Romero-Morales C, Pérez-Ruiz M, Lam-Meléndez A, Munguia-Izquierdo D, et al. Optimizing field body fat percentage assessment in professional soccer players. Appl Sci (Basel) [Internet]. 2022 [cited 2023 Mar 31];12(2):727.
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