What does 'endurance' refer to in physical conditioning?

Endurance in the context of physical conditioning refers to the ability to perform repeated activities over time, which is crucial for activities that require sustained physical effort. It encompasses both muscular endurance and cardiovascular endurance. Muscular endurance relates to the ability of a muscle or muscle group to sustain repeated contractions over a period, while cardiovascular endurance concerns the efficiency of the heart and lungs in delivering oxygen to the muscles during prolonged exercise.

This definition aligns with various physical activities, from running long distances to performing multiple repetitions in strength training. The other options focus on different aspects of physical performance, such as strength, speed, and agility, which do not encompass the essence of endurance as the capacity to sustain activity over time.