EFFECT OF CURVE AND SLOPE ON INDOOR TRACK SPRINTING
Keywords: athletics, sprint, indoor track, emg-recording, velocity
AbstractIn contrast with the standard 400 m outdoor track, indoor sprinting is performed on the more compact 200 m track. The curves of these indoor tracks are normally constructed by means of lateral slopes to reduce the centripetal forces acting on the contact foot of the sprinter. The centripetal force (Fc) is determined by the body mass (m) and the squared running velocity (v) of the athlete, as well as by the radius (R) of the curve: Fc= (m * v²)/R. The inhanging body position of the athlete reduces partly these centripetal forces. It is clear that runners in the inner lanes have to work harder than those running in the outer lanes. Therefore it was the purpose of this study to analyze the time differences among 200 m sprint performances in lane 2, lane 4 and lane 6 on the Flanders Expo track, that will host the European Indoor Championships in the year 2000. This track consists of a unique construction as the inclination axis of the lateral slope is situated in the middle of lane 2. This implies uphill running in lane 3 to 6 when entering the curve and downhill running in lane 1. When leaving the curve it is just the other way round. The runner in lane 2 has to run a flat course over the total distance. Five national level male sprinters performed a 120 m all-out sprint from starting blocks in lanes 2, 4 and 6. A comparable group of six sprinters performed a 120 m sprint, running full speed through the second curve of the 200 m track in the same lanes. The order of running the different lanes was randomised. Infrared sensors and an electronic timing system of Intersoft Electronics enabled the recording of the mean running speed in 15 different intervals. EMG-recordings were used to determine the duration of each stride. A mean 200 m-time was reconstructed by combining the interval times of both groups of subjects. The results of this study indicate that at the end of a complete 200 m run, lane 6-runners have a mean advantage of 0.23 s and 0.10 s compared to lane 2 and lane 4 respectively. Surprisingly this difference is mainly due to the advantage of the forwarded starting position in lane 6, avoiding the uphill running part of the first curve and benefiting optimally of the downhill part at the end of the acceleration phase. The main problem in lane 4 is the uphill running in the first steps of the acceleration. Because of their flat course lane 2-runners, compared to the uphill running in lane 4 and 6, can maintain their maximal velocity one interval longer on entering the second curve. But in the middle of this curve the outer lanes, compared to lane 2, take significant advantage of the greater radius. In spite of the difference in the radius of the curve there is no significant difference in running speed among lane 4 and lane 6. It can be concluded that lane 6 takes advantage of lane 4 in the first curve and makes the difference with lane 2 in the first as well as in the second curve. Analysis of stride characteristics shows that almost all significant differences in running velocity can be explained by differences in stride length. It can be concluded that the chances of an athlete in 200 meter indoor sprinting depend on the lane he is running in.
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