What effect does overload have on muscle fibers?

Overload is a fundamental principle in strength training that indicates that in order for muscles to adapt, they must be subjected to a greater than normal level of stress or resistance. This principle plays a critical role in muscle hypertrophy (growth) and strength improvements.

When overload is applied, it encourages the body to adapt to the increased demands placed on the muscle fibers. This adaptation is driven by an increase in muscle fiber recruitment, meaning that a greater number of motor units—groups of muscle fibers controlled by a single motor neuron—are activated during resistance training. This increased recruitment leads to not only stronger muscle contractions but also contributes to larger muscle size as the fibers are repaired and grow in response to the stimulus.

Furthermore, this overload can enhance both strength and muscular endurance, as the muscle adapts to perform better under the increased workload. Over time, consistent application of overload through progressive resistance helps in building muscle strength, size, and improving overall fitness levels.

In contrast, the other options either suggest misconceptions about the effects of overload or fail to recognize the fundamental adaptive responses of the body to increased stress.