What is the primary purpose of isometric exercises?

The primary purpose of isometric exercises is to improve muscular strength without movement. Isometric exercises involve contracting muscles against an immovable object or holding a position over a duration, which generates tension in the muscle without changing its length. This type of exercise is particularly effective for building strength in specific muscle groups, as it targets the muscles directly and allows for focused training without the need for extensive motion or equipment.

In contrast to other options, aerobic capacity training usually involves dynamic activities that promote endurance rather than static muscle engagement. Cardiovascular endurance enhancement also focuses on activities that increase heart rate through movement. Finally, promoting flexibility through active stretches is achieved through dynamic or static stretching rather than isometric holds, which do not involve a full range of motion necessary for flexibility improvements. Thus, option B accurately describes the unique benefits of isometric exercises in the context of strength training.