The present study was designed to investigate the kinematic and kinetic factors related to hurdle running velocity in comparison with sprint running. Movements during hurdle running (take-off, landing, and the 1st and 2nd steps after landing) and sprint running were filmed using a 16-mm movie camera, and the ground reaction forces of each step were recorded by a force platform. The joint torque and power of the hip, knee and ankle were computed from the film and force analysis data. The joint power curves were divided into eleven phases to calculate the mean power and mechanical work in each phase. The results are summarized as follows: 1) The horizontal velocity of the center of gravity decelerated in the first half and accelerated in the latter half of the foot contact period for all steps during hurdle running. As a result, the horizontal velocity of the center of gravity (=the amount of deceleration+acceleration) decelerated at take-off and accelerated at other steps during the foot contact period. 2) Although the amount of deceleration of the center of gravity in the first half of the foot contact period at take-off was positively correlated with hurdle running velocity (r=0.801, p<0.01), no correlations were observed at other steps during hurdle running and sprint running. 3) The amount of deceleration of the center of gravity in the first half of the foot contact period at take-off was correlated with the horizontal distance from the center of gravity to the toe at the moment of foot touch-down (r=0.844, p<0.0l). 4) The maximal velocity during the high knee movement phase of the take-off leg immediately before take-off was positively correlated with the hurdle running velocity (0.745, p<0.05). The mechanical work and the mean power during the high knee movement phase were also positively correlated with the hurdle running velocity (0.7l7, p<0.05; 0.812, p<0.05, respectively). These results suggest that performing high knee movement similar to that of sprint running reduces the deceleration in the first half of the foot contact period at take-off. 5) Faster hurdlers showed a higher swing-back velocity of the landing leg (r=0.848, p<0.01) and greater mechanical work in the hip extensors when lowering the leg (r=0.708, p<0.05). This suggests that lowering of the landing leg is an active movement due to the hip extensors, especially in faster hurdlers. 6) The knee joint angle at the beginning of the foot contact period upon landing and the minimum ankle joint angle during the foot contact period upon landing were positively correlated with the hurdle running velocity (r=0.758, p<0.05; r=0.667, p<0.05). These results suggest that faster hurdlers keep their center of gravity higher upon landing to reduce the impact force. This is consistent with the finding that faster hurdlers showed less mechanical work of the ankle extensors during the first half of the foot contact period upon landing(r=0.763, p<0.05). 7) The maximal swing-back angular velocity of the driving leg (represented by a line from the hip to the ankle) at all steps (take-off, landing, and the 1st and 2nd steps after landing) during hurdle running was positively correlated with the velocity (r=0.980, p<0.001; r=0.702, p<0.05; r=0.782, p<0.05; r=0.745, p<0.05, respectively). A similar result was obtained for sprint running (r=0.844, p<0.05). 8) The above findings suggest that faster hurdlers demonstrate similar hurdle running movements and muscle activities at take-off to those of sprint runners, and that their hurdle running movements and muscle activities at landing are more emphasized than those of sprint runners.
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