Here are some of the specific problems related to running shoe design flaws.
Achilles Tendonitis. Shoes that have inflexible soles cause the calf muscles to work harder and can contribute to the development of achilles tendonitis. The mechanical reason for this is the shoe and leg work as a fulcrum and lever system. With an inflexible sole it will make the lever arm function over a longer distance and make the tip of the shoe the location of the fulcrum, which you don't want.
To avoid injury the shoe should flex at the point where the toes join the foot, which also happens to be the widest part of the shoe. The shoe should also have a slight heel lift, which most running shoes do.
Shoes that have too much heel cushioning, including some of the air-cushioned models can also contribute to achilles tendonitis. After the heel strikes the ground, it continues moving, as the shoe's cushioning continues to absorbs shock. This continued motion can stretch a susceptible achilles tendon excessively.
Plantar Fasciitis. Shoes that are too flexible in the midsole or that flex before the point at which the toes join the foot result in forces that can both directly cause a stretch in the plantar fascia and contibute to excess pronation in the foot (subtalar joint). See Feb. 14 article for addtional information.
The lack of stability that exists in a shoe with this characteristic occurs not just at the transverse plane of the shoe where the shoe actually flexes, but also in a longitudinal plane, reducing the effectiveness of the shoe in controlling pronation.
Next week I will cover how the signs of wear on your running shoe can help you solve problems that may affect your ability to run injury free.
Go To Page: 1
