What is likely to be assessed with a skinfold measurement?

Skinfold measurements are primarily used to assess body composition, specifically the amount of subcutaneous fat in the body. The technique involves using calipers to pinch specific areas of the skin and measure the thickness of the skinfolds. This measurement correlates with overall body fat percentage and helps to estimate an individual's body fat distribution and muscle mass.

While body composition is a critical component of fitness assessments, the other options focus on different fitness attributes. Cardiovascular capacity pertains to an individual's ability to perform sustained exercise, which is typically assessed through aerobic fitness tests rather than skinfold measurements. Muscular flexibility deals with the range of motion in joints and is evaluated through specific flexibility tests. Aerobic fitness often involves activities such as running or cycling to measure endurance, not skinfold analysis. Hence, the skinfold measurement is specifically aimed at determining body composition, making it the correct answer.