Moderate exercise may not be enough to reduce stress levels. Exercising intensly forces you to focus your attention on the vigorous task at hand, causing dramatic and immediate reduction in stress. The tension built up in the body is released through the activity, whether it be driving a golf ball, lifting weights, sprinting, hitting a baseball. Many sports can be played at both moderate and intense levels. To see the maximal benefit of stress reduction, try to incorporate both into your activity! I know I never regret a tough workout, and pushing yourself provides the best results, both physically and mentally.