What assumption does hydrostatic weighing make regarding body composition?

Hydrostatic weighing, also known as underwater weighing, operates on the principle of Archimedes' principle, which states that the buoyant force on an object immersed in fluid is equal to the weight of the fluid displaced by the object. This technique uses the assumption of standard densities for muscle, bone, and fat to accurately calculate body composition.

This method relies on specific density values: fat mass has a lower density than water, while lean mass (muscle and bone) has a higher density. These established values allow practitioners to differentiate between fat mass and lean mass based on a person's overall density measured when submerged. By applying these standard densities, hydrostatic weighing can provide an estimate of body fat percentage.

While other factors may influence the accuracy of measurements (such as the distribution of body fat and body temperature), they do not directly relate to the foundational principles governing hydrostatic weighing as it is primarily concerned with the densities of the various body components. Understanding these density norms is crucial for the effective utilization of this assessment method.