For optimal stability, shoes with thin, hard soles are preferable for older individuals. Health professionals should exercise caution when recommending shoes with thick, yielding midsoles, such as running shoes, to unstable elderly individuals. Older men and women with a history of falls or who are obviously unstable, should avoid barefoot locomotion.

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Stable equilibrium during locomotion is required for both superior performance of sports and prevention of injuries from falls. A recent report indicated that currently available athletic footwear impairs stability in older men. Since this discovery, if confirmed, seems important to both competitive athletes and the physically active general public, we performed an experiment using similar methods on a younger population. We tested the hypothesis that midsole thickness is negatively, and hardness positively related to dynamic equilibrium, in 17 healthy adult men (mean(s.d.) age 33(11.13) years) via a balance beam method. Subjects walked along a 9-m long beam at 0.5 m sl once barefoot and six times wearing identical pairs of experimental shoes which differed only in midsole hardness and thickness which spanned the respective ranges currently available in footwear. Falls from the beam (balance failures) were quantified. Balance failures varied significantly in relation to midsole hardness and thickness, and there was a strong trend toward interaction of these variables (P = 0.09). Midsole hardness was positively related to stability, and midsole thickness was negatively related, which confirms the previous report. Hence, shoes with thick-soft soles, similar to modem athletic footwear and 'walking shoes', destabilize men, and shoes with thin-hard soles provide superior stability. The pair with the poorest stability (A 15 -thick; 12.34 balance failures per 100 m) produced 217% more balance failures than those associated with the best stability (A 50 -thin; 3.89 balance failures per lOOm).Since most types of athletic footwear and many other shoes incorporate midsoles with hardness and thickness associated with poor stability, we conclude that both athletic performance and public safety could be enhanced through stability optimized footwear. Footwear that incorporates expanded polymer foam of a certain range of thickness and hardness, which includes most commercially available athletic footwear, and presently popular 'walking shoes', has recently been reported substantially to impair equilibrium in older men. For example, these authors have shown that differences in fall frequency from a balance beam varied by an amazing 128%, when comparing footwear associated with the best stability with that of the poorest8. Since stability differences of this magnitude must have major health and athletic performance effects, products providing poor stability are currently being marketed to the general public specifically for use in performing physical activity (walking shoes and athletic footwear), and no safety standards are in force that can provide the public with relative stability with the use of these products. Further examination of the relation between footwear soles and stability seems justified.The previous report examined footwear midsole hardness and thickness exclusively in an older male cohort8. It seems unwise to assume that their results apply to the general population without testing a younger group. Accordingly, ...

A matrix of miniature and flexible pressure sensors is proposed to measure the grip pressure distribution (GPD) at the hand-handle interface of a vibrating handle. The GPD was acquired under static and dynamic loads for various levels of grip forces and magnitudes of vibration at different discrete frequencies in the 20-1000 Hz range. The EMG of finger flexor muscles was acquired using the silver-silver chloride surface electrodes under different static and dynamic loads. The measured data was analysed to study the influence of grip force, and magnitude and frequency characteristics of handle vibration on: (i) the local concentration of forces at the hand-handle interface; and (ii) the electrical activity of the finger flexor muscles. The results of the study revealed high interface pressure near the tips of index and middle fingers, and base of the thumb under static grip conditions. This concentration of high pressure shifted towards the middle of the fingers under dynamic loads, irrespective of the grip force, excitation frequency, and acceleration levels. The electrical activity of the finger flexor muscles increased considerably with the grip force under static as well as dynamic loads. The electrical activity under dynamic loads was observed to be 1.5-6.0 times higher than that under the static loads.

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