Air displacement plethysmography

Body composition measurement in adults with whole-body air displacement plethysmography (ADP) technology

Body composition measurement in infants with whole-body air displacement plethysmography (ADP) technology

Air displacement plethysmography (ADP) is a method used to assess body composition, specifically body volume and density, from which body fat and lean mass can be calculated. This technique is based on the principle of Archimedes' principle, which states that the volume of an object can be determined by the volume of air it displaces. ADP is considered a safe, non-invasive, and accurate method for measuring body composition, making it popular in both clinical and research settings.

Overview

ADP works by measuring the amount of air displaced by an individual's body when they sit inside a sealed chamber, known as a BOD POD®. The BOD POD® is a key component of the ADP system and uses changes in air pressure within the chamber to determine body volume. Once the body volume is measured, body density can be calculated by dividing body mass (obtained from a scale) by body volume. Body fat percentage and lean body mass can then be estimated using established equations that account for the density of fat mass and fat-free mass.

Procedure

The ADP test procedure involves several steps. Initially, the individual is weighed using a precise scale. Next, the individual enters the BOD POD® chamber wearing minimal clothing and a swim cap to minimize the trapping of air in clothing or hair. The individual sits quietly while the machine measures the air displacement caused by their body. The process typically involves two measurements of 45-50 seconds each to ensure accuracy. The data collected by the BOD POD® is then analyzed to calculate body volume, density, and composition.

Advantages

ADP offers several advantages over other body composition measurement techniques:

• Non-invasive: Unlike methods that require bodily samples or exposure to radiation, ADP is completely non-invasive.
• Quick and Easy: The entire ADP process takes about 5 minutes, making it a quick method for assessing body composition.
• High Accuracy: ADP is considered to have a high level of accuracy, comparable to hydrostatic weighing, but without the inconvenience of submersion in water.
• Safe for Various Populations: ADP can be used safely on a wide range of individuals, including children, elderly, and those with disabilities.

Limitations

While ADP is a valuable tool for body composition analysis, it has some limitations:

• Cost: The equipment required for ADP is expensive, which can limit access to the technology.
• Clothing and Hair: The need to wear minimal clothing and a swim cap can be uncomfortable or impractical for some individuals.
• Physical Constraints: The size of the BOD POD® chamber may not accommodate very large individuals.

Applications

ADP is used in various fields, including sports science, nutrition, obesity research, and clinical settings. It helps in assessing the effectiveness of nutrition and exercise programs, monitoring changes in body composition over time, and evaluating health risks associated with high levels of body fat.

Conclusion

Air displacement plethysmography represents a significant advancement in body composition analysis. Its accuracy, safety, and ease of use make it an important tool for researchers, healthcare providers, and fitness professionals. Despite its limitations, ADP provides valuable insights into an individual's health and physical status.