Muscular strength is primarily measured by what factor?

Muscular strength is primarily measured by the maximum weight lifted in one effort. This measurement reflects the greatest amount of force that a muscle or group of muscles can generate in a single, maximal contraction. It is often assessed using exercises such as a one-repetition maximum (1RM) test, where the individual attempts to lift the heaviest weight possible for one complete repetition.

In contrast, the endurance of muscle contractions focuses on how long a muscle can sustain activity before fatigue sets in, which assesses muscular endurance rather than strength. The speed of muscle recovery pertains to how quickly muscles can return to their baseline state after exertion and does not directly measure the capability of a muscle to exert force. Lastly, the flexibility of muscles during stretching evaluates the range of motion around a joint and the ability of tendons and ligaments to elongate, which is also unrelated to muscular strength. Therefore, the measure of maximum weight lifted effectively captures the essence of muscular strength, making it the correct choice.