A warm-up should slowly increase your heart rate and breathing. A warm-up is not solely a time to stretch. Don’t hold your stretches at this point and move your body gently to get going. The perfect warm-up is to do a lower intensity version of whatever exercises you are about to do. If you are about to go running, start with a slow walk and build the intensity. If you are about to take a long bike ride, start cycling slowly on a flat surface before you hit the hills and high speeds. Your goal during this time is to start to increase the temperature of your muscle tissue to prevent injuries.   Your workout should then be followed by a similar cool down period, which is the reverse concept of a warm up. You want to slowly decrease your heart rate and breathing, gently decreasing the intensity of whatever form of exercises you have chosen.   The optimal time to stretch and hold a static stretch is following your workout. Your muscles have just undergone repeated tightening and shortening from all the contractions of exercising and are still warmed up. Stretching helps relax your muscles and will improve your flexibility. Never stretch to the point of pain, though. Stretching feels like “ah–that feels good.” Pain feels like “ouch–that’s too much!”   Too many people think they can save time and take a shortcut by skipping the stretching. Not true! If you don’t attend to your muscles after working out, you’re looking at a stiff and sore payback tomorrow. If you are stiff and sore, you aren’t going to work out.   Here are a few good stretches for after your walk: Warm-Up and Cool Down.