STRIDE CHARACTERISTICS RELATED TO RUNNING VELOCITY IN MAXIMAL SPRINT RUNNING
Keywords: athletics, sprint, velocity, stride characteristics, emg-recording
AbstractIn sprinting, athletes and coaches strive to increase running speed by means of general and specific training methods. As running velocity is always the product of stride length and stride frequency, in the end, all methods aim to improve one or both of these factors. The relation between stride length, stride rate and running velocity has been discussed in the literature from different points of view. Alexander and Goldspink (1977) analysed the movement speed and stride characteristics of mammals. As they wanted to compare mammals of different sizes, they transferred stride characteristics and speed into dimensionless parameters, taking into account gravity and the length of the leg. Their conclusions should also be valid for humans. But it is not clear if these formulas can predict stride characteristics in maximal sprint running. It was the purpose of this study to analyse whether stride rate and stride length in maximal sprint running are related to running velocity as proposed by Alexander and Goldspink. A better understanding of this relationship could probably help coaches in developing sprint training strategies. In this study twenty male physical education students performed a maximal sprint over 100 meter and seventeen female students ran a 40 meter sprint. Running speed was continuously recorded by means of a velocimeter. Surface electrodes were used to record the muscle activity of four thigh muscles. These EMGrecordings were used to determine the duration of each stride cycle and to calculate mean stride rate per 5 meter-interval. The length of the lower limbs (h) and the acceleration of free fall (g) are used in the definitions of dimensionless running velocity (dV), stride rate(dSR) and stride length (dSL). The average maximal velocity of the male sprinters was 9.37 ±0.52 m/s while the female sprinters attained 7.38± 0.52 m/s. The relation between stride length and running velocity in male 100 meter performance was determined by means of linear regression analysis: dV=0.178+(1.175*dSL). This means that 87% of variance in running velocity seems to be related to differences in stride length. On the other hand variance in stride rate explains less than 20% of the variance in running speed. These findings are confirmed by the results in the 40 meter sprint of the female group: dV=(1.172*dSL)-0.0830 with 80% of variance in dV being explained by variance in dSL and 20% of dV explained by dSR. In contrast to the findings reported in the literature we found a clear linear relationship between dSL and dV, and no significant correlation between dSR and dV. These findings were confirmed in two separate analyses: one with females and another with males. The discrepancies between the results in the literature and this study can probably be explained by the fact that we analyzed pure sprint performances, in contrast to most studies analyzing differences in running speeds ranging from jogging to sprinting. In all-out sprinting, stride rate in the second 5 meter interval is already close to the maximum stride rate; from this point on differences in running speed are mainly due to changes in stride length.
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