A gentle stride of the foot and leg will feel smooth and natural. Walking or running within the natural range of motion for each, allows the muscles, tendons and joints to work together as a team. Gentle movement also stimulates the production of endorphins which boost attitude as they reduce aches and pains.
The most common pain-producing mistake, when beginning or when increasing the pace of a walk or run, is using a stride that exceeds your natural range of motion. The extra forward reach of the leg aggravates the hamstring (the muscle on the back side of the upper leg) and the tendon complex behind your knee. This “overstride” also stresses the shin muscle on the front of your leg.
A stride that is only half an inch too long (or longer) can also aggravate the back and hips. Each extended step increases the twist, or torque, of hips and spine. Even a few minutes of this can result in soreness the next day. But when the overstride continues for an hour of hiking, running, or powerwalking, pain may linger for days or weeks.
Many runners and walkers who don't overstride on the street or sidewalk will do so on a treadmill. When using a “tread” for the first time, or after a long layoff, it's best to slow the pace down and use a shorter stride than usual. Remember, you should control the speed of this machine.
At the end of a workout, it's easy to overstride. In the rush to get the workout done, it's very tempting to reach out with the lower leg. It may take a little management of the ego to slow down during the last 5 minutes so that you'll maintain a smooth motion. Practice shortening the stride at the end of all of your runs or walks to get into the habit.
When you're not sure about your length of stride, shorten it. Since all of the significant leg motion problems I've seen in coaching walkers and runners are the result of a long stride, I suggest being sensitive to tightness in the hamstring, hips or shins. A simple reduction of stride length can keep things from aching.
Take walk breaks or shuffle breaks. A major source of injury is the constant use of muscles, tendons, joints, etc. in the same way. By reducing the intensity and specific motion early and often in the exercise, you can avoid the problems. Runners should insert a one minute gentle walk break after running for 1-4 minutes. Walkers experience the same benefit when they use a “shuffle” of 30 seconds, every 3-4 minutes, from the beginning of the workout. The shuffle is performed by reducing stride length and effort down to “baby steps” for half a minute.