Fig. 4.

The “A” curve is a typical dose-response curve to physical exercise. Moderate exercise increases the physiological function of different organs, increases the rate of prevention against diseases and improves quality of life. Physical inactivity, strenuous exercise and overtraining increase the risk of diseases and decrease physiological function. The “B” curve indicates that regular exercise can extend or stretch the levels of ROS that are associated with high levels of physical function. This means that exercise can increase tolerance against high levels of ROS and can be preventive against oxidative stress- associated diseases.