Which of the following is a physical benefit of exercise?

Improved quality of sleep is recognized as a significant physical benefit of exercise. Engaging in regular physical activity helps regulate sleep patterns, making it easier to fall asleep and stay asleep throughout the night. This is largely due to exercise's ability to reduce anxiety and stress, which are common culprits of sleep disturbances. Additionally, exercise can promote deeper stages of sleep, contributing to overall restfulness and recovery.

While the other options may seem appealing, they are more related to social or psychological aspects rather than direct physical benefits. For instance, improved social skills and enhanced academic performance are outcomes that can arise from participating in group exercises or sports, but they do not directly correlate to the physiological effects of exercise. Increased stress levels, on the other hand, are the opposite of what regular exercise typically achieves. Thus, the most accurate answer regarding physical benefits of exercise is the improvement in sleep quality, reflecting the positive impact of a consistent fitness regimen on the body.