Which of the following exercises is useful for improving strength?

The choice of sit-ups as an exercise for improving strength is well-founded because sit-ups are a targeted abdominal exercise that specifically focuses on strengthening the core muscles. The core is essential for maintaining balance, stability, and proper posture during various physical activities, including dance. By performing sit-ups, individuals engage the abdominal muscles, which helps in building muscular endurance and strength in that area.

While running, swimming, and dancing do contribute to overall fitness and can help improve muscular endurance, they are primarily aerobic activities. These exercises are more focused on cardiovascular health, stamina, and coordination rather than specifically isolating and strengthening particular muscle groups. Sit-ups, on the other hand, are a direct strength-building exercise that can be easily adjusted to increase difficulty, leading to enhanced muscle strength in the abdominal region. This makes sit-ups a valuable exercise for those looking to improve their strength, particularly in the core, which is crucial for many athletic and dance movements.