Tuesday, April 29, 2003

Nonergonomic! Athletic Footwear Unsafe due to Perceptual Illusions

Nonergonomic! Athletic Footwear Unsafe due to Perceptual Illusions
[人因工程 ]

Athletic Footwear Unsafe due to Perceptual Illusions

Modern athletic footwear provides remarkable plantar comfort when walking, running, or jumping. However, when injurious plantar loads elicit negligible perceived plantar discomfort, a perceptual illusion is created whereby perceived impact is lower than actual impact, which results in inadequate impact-moderating behavior and consequent injury.

Wearers of expensive running shoes that are promoted as having additional features that protect (e.g., more cushioning, "pronation correction") are injured significantly more frequently than runners employing inexpensive shoes (costing less that US $40)...

In addition, in barefoot populations running-related injuries are rare, which indicates that humans adapted to barefoot running run with lower impact than the unadapted group referred to above. This also suggests that the lower extremity is inherently durable and is made susceptible to injury by footwear use. Based on the above data, not withstanding unsupported claims by footwear manufacturers of improved protection with their products, it seems appropriate to consider expensive athletic footwear from major manufacturers (and perhaps less expensive shoes) as unsafe.

This is strengthened by reports indicating that, when habitually barefoot humans walk (and probably when they run), they have greater knee flexion, which has been shown to reduce shock.

Barefoot activity when practical (no need for thermal insulation; no risk of crush injuries; social acceptability) deserves consideration since plantar sensory mediated protective adaptations seem optimized for this condition. Although this may run counter to notions prevalent in economically advanced countries recounting dangers of barefoot activity and necessity of footwear even when barefoot activity is feasible, supporting data are lacking, and many have concluded that footwear design is guided by fashion rather than health considerations.

In summary, people who perform activities involving high impact while wearing footwear currently promoted as offering protection in this environment are at high risk for injury. Unlike the natural state (barefoot and natural surfaces), where impact is sensed and, through impact-moderating behavior, is maintained at a safe level, an inadequate understanding of the physiology of human impact control has resulted in footwear which makes chronic overloading inevitable by providing plantar comfort to the wearer even when enormous vertical impact is experienced.

Editor's Comments:

Household fuses sometimes blow out as soon as they are installed. Sometimes one after another. When they do, frustrated homeowners may resort to the "penny in the fuse box" trick. They wedge an ordinary copper penny in the socket where the fuse normally goes. Presto! No more blown fuses, and the lights stay on indefinitely, or until the house burns down around you. As any fire marshall will tell you, you might as well drench yourself with gasoline and light a match. That's how dangerous it is.

Providing an inordinate amount of "ergonomic" cushioning in footwear is the physiological equivalent of putting a penny in the fuse box. By masking the impact on one's feet, knees, even spinal column, "ergonomic" cushioning negates natural impact-moderating behavior that would have maintained physical activity at a safe level. The result is injury to the wearer, induced by the very item that was supposed to protect against injury.

The underlying principle is simple, yet powerful: "Nature knows best." To paraphrase a famous margarine commercial from many years ago, "It's not wise to fool Mother Nature!"

-- Bevin Chu

Explanation: Athletic Footwear and Chronic Overloading
Illustration(s): World Champion Barefoot Runner Zola Budd-Pieterse of South Africa
Author(s): Steven E. Robbins and Gerard J. Gouw
Affiliation: "Athletic footwear: unsafe due to perceptual illusions," Medicine and Science in Sports and Exercise, 23(2), 1991, pp. 217-224.
Source: http://www.barefooters.org/medicine/med_sci_sports_exer-23.2.html
Publication Date: December 27, 1996
Original Language: English
Editor: Bevin Chu, Registered Architect

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