MUSCULAR PRE-TENSION AND JUMPING: IMPLICATIONS FOR DIVE STARTS

Abstract

Isometric pre-tension has been shown to increase average torque in the leg extension movement. The effect of different levels of isometric pre-tension (PT) on vertical jumps has not been investigated. Twenty male University students completed a jumping task usirlg PT levels of 0, 40, 50, 60, 70 and 80% of a maximal voluntary contraction. The results were compared with those of a jump with a counter movement (CMJ). The CMJ had a significantly lower peak force than all other jumps. The rate of force development decreased with increased levels of PT. CMJ height was significantly larger than all PT jumps, with no difference in jump height between the PT levels. There was no change in reaction time with PT but time from a starting signal to take off was significantly less. This has implications in decreasing swimming dive start times.