Warming Up When exercising, it is very important to spend about ten minutes at the beginning before you start exercising to warm up your muscles. Never stop exercising without a cool down period as well. This should be about five minutes in duration. Always warm-up the muscle before stretching. Warm muscles and connective tissues are more pliable than cold ones. Stretching reduces the potential for injury by warming up and lengthening the muscles and connective tissue. Stretching after exercise reverses the tightening and shortening effect of exercise on the muscles and connective tissues. Under no circumstances should you bounce or lunge when stretching. You should not feel any pain while stretching. The following exercises are ideal for warming up. Please note that stretches should be held at the point when mild tension is felt in the muscle, and should be held for 20 to 30 seconds. Calf Muscles Stand with one leg in front, feet parallel and pointing forwards. Bend the front knee, keeping the back leg straight, pushing the heel into the floor to stretch the calf. Repeat the stretch for the other calf.