What is hydrostatic weighing primarily used for?

Hydrostatic weighing is primarily utilized for assessing body fat percentage due to its principle of water displacement and Archimedes' principle. This method involves measuring a person's weight in water and compared to their weight on land. The density of the body can be calculated from these two measurements, which, in turn, allows for the estimation of body fat percentage. Since fat is less dense than water, individuals with a higher body fat percentage will weigh less underwater than someone with more lean muscle mass. This makes hydrostatic weighing one of the most accurate methods for determining body composition, particularly the proportion of fat versus lean mass within the body.

The other options do not accurately describe the primary purpose of hydrostatic weighing, as it is not designed for measuring bone density, evaluating muscle strength, or tracking hydration levels. These aspects may be assessed through different methods or technologies specifically focused on those areas.