The relationship between knee joint angle, stretch-shorten cycle performance, and jump distance in ski jumping

Abstract

This investigation examined the relationship between knee angle, stretch-shorten cycle performance, and jump distance in ski jumping. 44 elite ski jumpers were video taped at 120 Hz. Hip, knee, and ankle displacements were digitized to examine the relationship between the knee joint angle, stretch-shorten cycle performance, and jump distance in ski jumping. Jump distance was recorded for comparison. Average distance jumped was 99.03 f 11.6 m. During the stretch-shorten cycle movement, the average amount of knee flexion was -6.6 + 3.9 " and the average amount of knee extension was 8.8 f 4.8 ". A significant (p = 0.014) quadratic relationship as found between the amount of knee flexion and jump distance. The knee-joint extension velocity averaged 9.2 f 0.8 radians/s, but was not found to be significantly related to jump distance. The quadratic relationship between jump distance and the amount of knee joint flexion demonstrated an optimal knee flexion range for maximizing jump distance. This study suggests that when elite jumpers utilize an optimal stretch-shorten movement, in combination with proper form on the take-off table and in the air, they produce longer jump distances.