RELATIONSHIP OF SHOE IMPACT, BRAKING AND PROPULSIVE FORCE
AbstractINTRODUCTION -Van Mechelen (1992) reported that runners having no preference for shoe brand sustained significantly fewer injuries This work aimed to investigate the influence of shoe type on ground reaction force during jogging. Ground reaction forces (vertical, anterior-posterior, mediolateral) were measured as the subjects right foot struck a 9581 Kistler force platform mounted in an outdoor profiex artificial track surface. Forces were sampled and stored using Orthodata Provec software running on a Viglen 386 computer system. Twelve sports students, six male (age 20.17 ±0.75 years; height 180 ±0,07m; weight 81.2 ± 7.0Kg (mean ±S.D)) and six female (age 19.7 ± 0.52 years; height 1.58 ± 0.15m; weight 61.0 ± 8.2Kg (mean ±S,D.)) were the subjects of the study. Following shoe habituation subjects jogged at preferred pace naturally in mild, dry conditions across the platform at least five consecutive times wearing each pair of shoes. Males wore 6 new pairs of shoes (Adidas Response Lite; Adidas Torsion Advance; Tech Performance; Puma Disc system TX4000; Puma Viento; Mizuno Mondo Elite) and females four pairs of shoes (Adidas Response Lite; Adidas Lady Tech Performance; Puma T-400; Puma liberte 11) in an individual random order. Jogging speeds were measured using infrared timing devices positioned 1m before and 1m after the force platform. Peak Forces were read subsequently from the computer screen using cursor measurement to locate peak forces. Following initial evaluation analysis was focused on the vertical and anterior-posterior torees. Mean peak vertical impact and maximal forces, mean peak braking and propulsive forces were expressed relative to each subject's body weight (BW), RESULTS -For the male subjects the mean peak vertical force range for alt shoes was 2.9 -3,OBW, impact force 2,5 -2.8BW, braking 0.62 -0.70BW, and propulsive OAO -OA4BW. For the females the mean peak range was vertical force 2.75 -2.78BW, impact force 2.1 -2.5BW, braking 0.57 -0.59BW, and propulsive 0.37 -0.41 BW. In both the male and female subjects a low mean peak braking force and low mean peak vertical impact force was associated with a high mean peak propulsive force (male: Adidas Tech Performance Braking 0.616BW, Impact 2.531 BW, Propulsive OA43BW; female: Adidas Response Lite Braking 0.572BW, Impact 2.072BW, Propulsive OA09BW). Similarly a high mean peak braking force and high mean peak impact force was associated with a low mean peak propulsive force (male: Puma Disc system TX4000 Braking 0.700BW, Impact 2.768BW, Propulsive OA02BW; female: Adidas Lady Tech Performance Braking 0.591 BW, Impact 2A82BW, Propulsive 0 379BW). Differences were significant (P < 005) CONCLUSION -For two shoe designs the existence of a lower vertical impact force and low braking force is associated with greater propulsive force.
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