What is meant by the term "muscular endurance"?

Muscular endurance refers to the ability of a muscle or group of muscles to sustain repeated contractions against a resistance for an extended duration. This characteristic is crucial for activities where prolonged effort is needed, such as swimming, cycling, or other sports that require sustained physical activity. When training for muscular endurance, individuals typically engage in higher repetitions with lighter weights, which helps improve the muscles' ability to perform over time without fatigue.

The other options describe different aspects of physical performance. The total amount of weight one can lift in a single attempt relates to maximum strength, which measures how much force can be exerted in a single effort. Maximum strength achieved in a single rep is again focused on maximal power rather than endurance. Lastly, flexibility over time pertains to the range of motion of muscles and joints rather than how long a muscle can perform repetitive actions. Thus, option B accurately captures the essence of muscular endurance.