Which of the following is NOT a sign of over-exertion?

Improved endurance is not a sign of over-exertion because it indicates a positive adaptation to training rather than a negative response. When individuals engage in regular exercise, their bodies adapt by enhancing their stamina and capability to perform physical activities over time. This improvement signifies that the person's body is effectively handling the stress imposed by the workouts, allowing them to exercise longer or at a higher intensity without experiencing excessive strain.

In contrast, the other options—nausea, fatigue, and chest pains—signal that the body may be under duress or that the workout intensity may be too high for the individual’s current fitness level. Nausea can result from excessive exertion or dehydration, while fatigue often surfaces when the body is pushed beyond its limits. Chest pains can indicate serious potential issues, such as cardiac distress. Overall, improvement in endurance reflects healthy adaptation to exercise, distinguishing it from signs that suggest over-exertion.