N Krouglicof | PubMed Health

PubMed1998

Improving balance.

OBJECTIVE: To test the hypothesis that shoes made with a sole material that retains compressed thickness between steps (low resiliency) provide balance better than and comfort equal to shoes composed of high resiliency sole material. SETTING: Older subjects were recruited from a medical clinic population, and younger subjects came from a recreational sports population. DESIGN: A randomized-order, cross-over, controlled comparison design. PARTICIPANTS: Groups comprised random samples of 30 older (mean age 66 years, SD+/-3.0), and 30 younger (mean age 34 years, SD+/-6.0) healthy men who met age selection criteria. MEASUREMENTS: Stability was inferred by sway measures: sway velocity (cm x s(-1)), X-Y area (cm2), and radial area (cm2). Comfort was measured by direct scaling and magnitude estimation using an 11-point ratio scale. RESULTS: Stability inferred by sway velocity was 311% (P < .001) and 31% (P < .001) poorer for younger and older groups, respectively, for high and low resiliency interfaces. Sway velocity with low resiliency interface was lower than bare platform, the lowest ever recorded under equivalent conditions (P < .001). All interfaces were equally comfortable. CONCLUSIONS: Stability rises with low resiliency interfaces and declines with high resiliency interfaces: sway velocity in older people wearing hard-soled footwear incorporating low resiliency technology would be 20% lower than in younger people wearing most current athletic and walking shoes. Inasmuch as existing theory can not account for improved balance with interfaces, we propose that when humans are supported by rigid support surfaces, elastic biologic tissues store energy from postural adjustments and locomotion, which is returned as a reaction force causing overshoot. This amplifies frontal plane foot movement and attenuates foot position awareness, causing less precise postural adjustments and instability. Low resiliency interfaces dissipate energy and thereby moderate overshoot. Low resiliency interface technology is capable of improving stability, which portends improved health for unstable older people in particular.

Adult↗

PubMed1997

Foot position awareness in younger and older men: the influence of footwear sole properties.

OBJECTIVES: To test the hypotheses that foot position awareness is related positively to stability, positively to shoe sole hardness, and negatively to shoe sole thickness, and that foot position awareness declines with advancing years. SETTING: Older subjects were consecutive volunteers from a medical clinic; younger subjects were volunteers from the community. DESIGN: Randomized-order, cross-over, controlled comparison. PARTICIPANTS: Older subjects were a random sample of 13 healthy men, mean age 72.58 years, SD +/- 4.50. Younger subjects were a random sample of 13 male subjects from the general population, mean age 28.13 years, SD +/- 3.96. Additional selection criteria were absence of disabilities influencing ability to walk and no history of frequent falls. MEASUREMENTS: Balance failure frequency, defined as falls per 100 meters of beam walking; rearfoot angle in degrees, measured via an optical position measurement system; perceived maximum supination when walking, in degrees, estimated by subjects using a ratio scale; foot position error, in degrees, was defined as the rearfoot angle minus perceived maximum supination. RESULTS: Foot position error during walking: (1) increases with advancing years; footwear conditions absolute mean error for older sample of 15.48 degrees, SE +/- 1.56 degrees, and younger sample 5.44 degrees, SE +/- 1.03 degrees (P > .001); (2) is positively related to stability (r = .367, P < .001); (3) is positively related to midsole thickness (F(1,11) = 19.89, P < .001); (4) is negatively related to midsole hardness (F(2,22) = 29.80, P < .001); (5) correlates best with perceived maximum supination (r = .901, P < .001). CONCLUSION: Foot position awareness is related causally to stability; shoes with thin, hard soles provide better stability for men than those with thick, soft midsoles. Foot position awareness declines with advancing years.

Adult↗