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Jpn J Biomechanics Sports Exercise 9(2):53-68, 2005

Change in kinetics of the support leg during the curve phase in long distance speed skating

Jun YUDA1), Masahiro YUKI2), Toru AOYANAGI3), Norihisa FUJII4), Michiyoshi AE4)

1) Department of Sports Sciences, Japan Institute of Sports Sciences,
2) Faculty of Education, Shinshu University,
3) Japan Skating Federation
4) Institute of Health and Sport Sciences, University of Tsukuba

Abstract

The purpose of this study was to investigate three-dimensional kinetic changes in the support leg during the curve phase in long distance speed skating. Eight male long distance speed skaters performed 4000 m skating at the maximal effort, using an instrumented sensor klapskate. The skaters were videotaped with two synchronized cameras (60 fields/s) in the mid portion of the curve track by using a panning DLT technique. Push-off forces and three-dimensional coordinates of the segment endpoints and blades during the left stroke were collected over 4000 m distance to calculate kinetics of the left support leg in the first and second halves, the points of 650 m and 3450 m, by an inverse dynamics. The contribution of the knee joint to total mechanical work done by the leg joints decreased in the second half, and the positive work done by knee joint torque in the second half was smaller than that of the first half. In the first half, the hip and knee joints exerted large extension torques during the gliding phase, and the knee joint exerted large extension torque and power during the push-off phase. The knee extension torque after approximately 30% stroke and extension power of the knee joint during the push-off phase in the first half were larger than those of the second half. These results indicate that minimizing the decrease in the knee extension torque of the left support leg under fatigue condition is an important factor to maintain the skating speed in the curve phase of the long distance speed skating.

Key Words: kinetics, maintaining the skating speed, three-dimensional motion analysis, panning DLT method

Submittted for Publication : March 15, 2005,

Accepted for Publication : May 10, 2005

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