If you're like most people, you've stretched before a workout or playing sports. Doing so should help you get your muscles ready to work. While stretching is good for your muscles, you're wasting your time if it's the first thing you do.
"Stretching is not a good warm-up. Most people don't do this, but flexibility exercises should be done after a good warm-up or at the end of an exercise session. In fact, most people skip flexibility exercises altogether, which is a mistake. Warming up literally increases the muscle temperature and prepares the muscle for the physiologic (metabolism) and biomechanical (contraction) demands of more intense exercise. It can also increase range of motion, which may prevent injury.
"A good warm-up should be at least 5-10 minutes of aerobic/endurance exercise done at a lower intensity than the workout (or event or sport) that emphasizes the muscles you will use. A practical recommendation is to do a whole-body exercise (rowing machine, elliptical machine, etc.) for 5-10 min before starting your workout. There are also a lot of whole-body exercises that don't involve equipment that are good alternatives."
When you're warming up, remember to do low intensity exercise first. If you don't have the suggested equipment, Dr. Parr recommends this full-body warm up. He also suggests 5-10 minutes of similar, lower-intensity exercise after the workout to cool down, as blood may pool in the legs and takes some time to get back up to the heart and brain. If you just stop, you can become dizzy because the blood doesn't get pushed back up.
While some people get away without proper warm-ups and cool-downs before and after exercise, employing both can help prevent injury and discomfort. That's why you should always do both, and save your stretching for afterwards.