When you wear shoes, you're much more likely to heel strike. from http://www.barefootrunning.fas.harvard.edu/4BiomechanicsofFootStrike.html http://www.barefoo

When you wear shoes, you're much more likely to heel strike. from http://www.barefootrunning.fas.harvard.edu/4BiomechanicsofFootStrike.html http://www.barefootrunning.fas.harvard.edu/4BiomechanicsofFo...: "In heel striking, the collision of the heel with the ground generates a significant impact transient, a nearly instantaneous, large force. This force sends a shock wave up through the body via the skeletal system. In forefoot striking, the collision of the forefoot with the ground generates a very minimal impact force with no impact transient." In other words, your knees, hips, and back act as shock absorbers when you heel strike. Try this experiment - jump into the air, landing on your heels. Then jump, landing on the balls of your feet. How does each one feel?