Which type of exercise is likely to improve muscular endurance the most?

High-repetition activities are highly effective for improving muscular endurance because they are designed to enhance the muscle's ability to sustain prolonged efforts over time. This type of exercise typically involves lifting lighter weights for a greater number of repetitions, which directly targets the muscle fibers responsible for endurance. When muscles are engaged in repeated contractions over extended periods, they adapt by becoming more efficient at utilizing oxygen and managing fatigue, thereby improving overall endurance levels.

In contrast, heavy weightlifting primarily focuses on increasing strength and power through lower repetitions with heavier weights, which does not contribute significantly to muscular endurance. Single-sprint efforts involve short, explosive bursts of activity, which are more aligned with improving speed and power rather than endurance. Isometric holds, while they can enhance muscle stability and strength at specific joint angles, do not involve movement through a range of motion, making them less effective for endurance improvements. Thus, high-repetition activities are the most suitable choice for developing muscular endurance.