"Stretching is an excellent way to cool down, rebalance your body, and alleviate muscle strain," explains Beth Shaw, founder of YogaFit, Inc., a yoga-centered training company based in southern California. Walking stresses the lower back and tightens the hamstrings and hips, says Shaw. "If you don't stretch, muscles can shorten, resulting in injuries." Lie flat on your back. Bend your right leg and rotate it to the left. Look over your right shoulder and breathe. Repeat on the other side.