INFLUENCE OF THE FOOTBALL BOOT DESIGN ON SHOCK ABSORPTION
AbstractINTRODUCTION: A number of studies about the importance of sports shoe design on injuries prevention have been published in late years (Masson, 1989;Stacoff, 1988). Epidemiological studies indicate that football has special relevance with relation to suffering injuries (Hoff,1986; Ydes, 1990). During the practice of football a number of movement patterns such as jumping or running are performed(Reilly, 1976), being shock absorption a basic criterion for the design of footwear in Worts where such movement patterns occur. To improve the shock absorption of footwear two strategies are often adopted: to potentiate the natural mechanisms by means Of a better the tissue heel Or to increase the shock absorption capability of the footwear appropriately selecting the materials of the sole and insole. The aim the study was to evaluate the effect which different boot designs and different sole and insole materials had on load transMission during running. Based on a preliminary study, 3 boot prototypes and 4 insole prototypes were made. 8healthy football players were selected and they performed 6 runs with each of the 12possible combinations of boot/insole. The runs were performed in a football field and a speed of 4 m/s was determined controlled by electric photocells. The sequence of each condition was randomized for each subject. The subjects were instrumented with 2 accelerometers, attached to their skin by means of a strong bandage on tibia and forehead. The signals from the accelerometers were connected to a telemetry equipment which allowed the subject freer movements. With parameters obtained, an analysis of variance (ANOVA) was made. The level of significance chosen was of alfa < 0.05. To analyze the differences between conditions, an LSD test was made. RESULTS: One of the viscoelastic materials inserted in the insole offered a mean reduction of impacts of about 6%.One of' the materials of the boot sole showed a better capability of shock absorption, about 7%. The boots to which a special compartment for the heel pad did not improve shock absorption. Acceleration measured at tibia was of 6.01+0.06 times gravity (g) and at head it was of 2.45+2g.CONCLUSION: According to the results, an appropriate selection of insole and boot materials an improvement of shock absorption of 13% can be obtained. Although the tests were made on a natural grass football field and the speed of run was not too high, the values found for both tibia and forehead were high: this fact confirms the hypothesis that shock absorption is a basic criterion in the design of football boots from the point of view of protection from injuries. REFERENCES: Hoff, G.L and Martin, T.A.(1986). Outdoor and Indoor soccer: Injuries among youth players. Am. J. Sp. Med. 8,231-233.Masson, M. and Hess, H. (1989) Typicalsoccer injuries. Their effects on the design of the athletic shoe. In 6. Segesser & W.Pforringer (Eds.) The shoe in sport.London: Wolfe Publishing, Lld., 89-95.Reilly, T. (1 976) A motion analysis of work rate in differential roles in professional football match play. J. Human Mov. Stud.2, 87-97.Stacoff, A,; Denoth, J.; Kaelin, X. and Stuessi, E. (1988) Running injuries and shoe construction: Some possible relantionships. lnt. J. Sports Biomech. 4,342-357.Yde, J. and Nielsen, A.B. (1990) Sport injuries in adolescents' ball games: soccer,handball and basketball. Br. J. Sp. Med24(1), 51-54.82
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