Which of the following is a physiological effect of excessive stress on an athlete?

The physiological effect of excessive stress on an athlete that is most significant is increased susceptibility to injury. When athletes experience excessive stress, whether from physical training, competition, or psychological pressures, it can lead to a variety of negative physiological responses in the body. Elevated stress levels activate the body's stress response, which can result in heightened muscle tension, impaired coordination, and decreased focus.

These factors contribute to an increased risk of injury since tight muscles may not function optimally, and mental distractions can lead to lapses in attention. Additionally, the body's recovery processes may be compromised under stress, making it harder for athletes to repair their muscles and tissues adequately after training or injury. Therefore, excessive stress can diminish physical performance, making athletes more vulnerable to both acute injuries and overuse injuries due to fatigue and decreased mental acuity.

In contrast, enhanced muscle recovery, increased injury resistance, and improved cardiovascular function are not effects associated with excessive stress; in fact, they are benefits typically linked to a well-managed training regimen and balanced stress levels.