The majority of Sport Walking Shoes as already stated are not well designed. The one item that appears to be well designed about them is their marketing strategy. The usually observed flaws in their design follow:
Specific Problems Related to Running Shoe Design Flaws
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 that the looking at the shoe and leg as a fulcrum and lever system, they make the lever arm function over a longer distance and make the tip of the shoe the location of the fulcrum. 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.
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). 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.
Shoe Wearing & Buying Tips
A shoe's midsole only lasts so long. It degrades from use and the resultant useful life of a running shoe is 350 to 550 miles. This means that if you are running 20 miles a week, you should consider changing by approximately weeks 20 to 25. The shoe may still serve a useful purpose; casual wear for walking.
Sole wear does not necessarily reflect the loss of shock absorption by a shoe. Even with a new looking shoe, adequate shock absorption may be lacking. Use the 350 to 550 mile guideline instead of trying to guess how worn your shoe should look.
Buy your shoes at the end of the day, when your feet are somewhat larger from the day's walking.
Make sure there is about a finger's width at the front of the shoe. This will help prevent runner's (black) toe. The shape and depth of the front of the shoe also have an effect on this problem.
If you have had no problems while running in a shoe, you should probably try to obtain another pair of the same make and model.
Don't even dream of running a marathon in a new pair of shoes. Your shoe should have at least 100 miles on it to be broken in well enough to run a marathon.
Make sure you carefully lace your shoe before running. Too tight a shoe may make parts of the top of your foot sore or squeeze your metatarsals too tightly. Too lose a shoe may make your foot move excessively and be less stable, resulting in more than normal pronation.