How is "muscular endurance" best defined?

Muscular endurance refers specifically to the ability of a muscle or group of muscles to sustain repeated contractions over a period of time without experiencing fatigue. This definition emphasizes the capacity to maintain performance levels during prolonged activities, such as running, cycling, or performing multiple repetitions in weight training.

Factors that contribute to muscular endurance include the efficiency of energy systems, muscle fiber type, and the ability to utilize oxygen effectively. It is distinct from muscular strength, which focuses on the maximum force that a muscle can produce in a single contraction.

In contrast, the other definitions provided do not align with the concept of endurance. One defines strength in terms of a single force, while another focuses on maximum force exertion, and yet another describes the speed of muscular contraction. Together, these highlight properties of muscle performance that do not encompass the sustained effort characteristic of muscular endurance.