What physiological change occurs when muscles are continually stressed during exercise?

When muscles are continually stressed during exercise, they undergo a process of microtrauma, where small tears occur in the muscle fibers. This is a normal response to the stress of resistance training or heavy exertion. After the exercise, the body initiates a repair process where these microtears are healed, and as a result, the muscle fibers adapt and become thicker and stronger. This adaptation is known as hypertrophy, which is the physiological basis for muscle growth.

This process is vital for improving strength and endurance, supporting athletic performance, and enhancing overall fitness. The body’s ability to repair and adapt to these stresses is a key component of physical training. Additionally, experiencing muscle soreness after such exercises is often a sign of this microtrauma and subsequent repair process.

In contrast, the other options do not accurately describe the physiological changes that result from exercise stress. For example, while muscles do become stronger over time, they do not become heavier due to exercise itself; rather, they adapt in strength and density. Also, muscles can experience soreness, which contradicts the idea that they "never experience soreness." Lastly, exercise typically increases blood supply and circulation to muscles as the body works to deliver oxygen and nutrients needed for recovery, rather than causing a