On taking a step, the foot normally flexes approximately 54 degrees at the ball on the bare foot.

But all shoes flex 30 to 80 percent less than normal at the ball. This obviously creates flex resistance for the foot by the shoe. The foot must now work harder to take each or its approximately eight thousand daily steps. The required extra energy imposes undue strain and fatigue on the foot.

Why are most shoes inflexible? First, the average shoe bottom consists of several layers or materials or components: outsole, midsole, insole, sock liner, filler materials, cushioning. This multiple-layered sandwich poses a formidable challenge to bending or flexing. Second, many types of footwear — athletic, sneakers, work and outdoor boots, walking, casual, etc. — have thick soles which add further to inflexibility.

Many elderly people whose feet have lost elasticity and flexibility over the many years of shoe wearing have difficulty climbing or descending stairs. They must use stair rails for pull-up power and security.

The National Safety council reports that in 1994 (latest figures) 13,500 fatalities occurred from stair falls — and 2,500 of the victims were over age 65. An even greater number or casualties from stair falls resulted in serious injuries (fractures, sprains, etc.), occurring with people of all ages. Climbing and descending stairs requires both foot flexibility and the lift power from the Achilles tendon and calf muscles. If both have been diminished and handicapped by habitual shoe wearing, then the stability and security of the gait itself are diminished and handicapped.

Most people, including medical practitioners and shoe people, test for shoe flexibility in a wrong manner, by grasping the shoe at both ends and bending the sole. But that flexes the shoe behind instead of at the ball. If the foot were flexed in the same manner, the five metatarsals would be fractured.

To properly test for flexing, rest the shoe sole down on a table or counter. Insert one hand inside, using a couple of fingers to press down on the ball. With a finger of the other hand, lift the toe tip of the shoe. If the toe end, tip to ball, lifts easily, the shoe is flexible. The degree to which it resists toe lift is the degree to which it is inflexible.

The more inflexible the shoe, the more flat-footed the gait manner. With inflexible or semi-flexible shoes (which include most) the step push-off is almost wholly from the ball, thus fulfilling only half to three-fourths of the natural step sequence.