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Stretching helps flexibility, which makes your stride better.  Use dynamic stretches that move your body while stretching. For instance, start by swinging your arms frontward and backward, then moving on to twisting the top half of your body around to each side. Next, try forward lunges. Step forward with one knee, bringing the other knee almost to the ground. Step forward with the other leg, bringing the other knee almost to the ground. Continue forward with the lunges.  Move on to exercises that will warm up your muscles. For instance, you can hop in place. You can also jog slowly in place bringing your knees up high, and then jog slowly in place while trying to pull your heels up higher in the back as you jog. Faster runners actually take more steps than slower runners.  One way to shorten your stride is to run while jumping rope. That is, take the jump rope out to the track with you. Start out how you would normally jump rope, using two feet.  Begin alternating feet, running in place while jumping.  Move forward while jumping. Once you get the rhythm, start running around the track while still using the jump rope. The jump rope helps rein in your stride.  Another way to shorten your stride is to count your steps in a minute, and then try to up that number little by little. That is, maximize your oxygen intake by using your nose and mouth to inhale and exhale. Your muscles need oxygen to work their best. Take some time to focus on your breathing. As you're running, concentrate on breathing through both your mouth and nose at the same time and blowing air out through both at the same time. If you notice you're only breathing through one or the other, take a moment to focus and correct it. Keep your posture good, and hit the ground with the middle of your foot. Your foot should land below your hip. For good posture, imagine you have a string running up your back that keeps everything upright and straight. Keep your chin up, literally, and focus ahead. Also, try to relax your body, including your shoulders, neck, and jaw. A treadmill forces a pace, which means you must go that fast, which can increase your speed over time. Try going for a particular interval at a slightly faster speed than normal. While running on the treadmill, increase the pace for 1 to 5 minutes, then push it back down. Focus on swinging your arms close to your body, which will also help keep your legs inline. Keeping your legs inline is better technique, which can help your run faster.
Stretch and warm-up before you run. Shorten your stride. Let your muscles breathe. Work on form. Use a treadmill. Make your arms work for you.