Walking is one of the safest and most effective sports for fitness, but to become fit, you have to move fairly fast. You should exercise vigorously enough to increase your heart rate at least 20 beats a minute more than when you rest. Walking at a leisurely pace will not raise your heart rate very much. You can increase your speed by taking longer steps or by moving your feet at a faster rate.
To lengthen your stride, swivel your hips so that you reach out further forward with your feet. This causes you to twist your body from side to side, which forces your toes to point to the outside when your feet touch the ground. By pointing your feet forward after your heel strikes the ground, you will gain a few inches. To move your feet at a faster rate, you have to move your arms at a faster rate also. Every time one leg moves forward, the arm on the same side moves back and the arm on the other side moves forward. For every step forward, there is an equal number of arm movements forward. To move your arms faster, you have to keep your elbows bent. The fulcrum of your arm swing is at your shoulder. The straighter your elbows, the longer your arms swing as a pendulum from your shoulder, reducing the frequency of arm swings. Bending your elbows shortens the swing and allows you to move faster.