RELIABILITY OF DROP JUMP VARIATIONS IN PERFORMANCE DIAGNOSTICS

Abstract

In several sports athletes have to produce maximal power for accelerating the body and/or sport equipment (e.g. long jump, shot putt, basketball, etc.). The primary indicator used for estimating power output in drop jumps are the peak force rate (Fex) and the peak force (Fmax). These variables also characterise the reactive force ability of an athlete during a stretch-shortening-cycle (SSC). In order to use the accumulated energy produced in the eccentric phase during the concentric contraction, the contact please revise must not be longer than 200 ms (Komi 1984). Reactive force abilities are commonly tested in drop jumps (DJ). The accomplishment of DJ is variously described in the literature, so no standardized conditions are given (Baca 1999). One corresponding aspect is the arm position (free arm-swing vs. arms akimbo). Particularly, jumps with arm-swing require a higher grade of coordination (e.g. basketball) and are associated with an enhanced jump height. DJs with arms akimbo are often used in subjects with less sports experience or if the performance diagnostics primarily focuses on the power output in isolated leg extensions. Another aspect is the method of calculating the jump height from the measured force data. The calculation of the jump height from the momentum (based on the force-time-curve) might be inaccurate as the exact drop height is not known. Consequently, the jump height often is calculated from the flight time. This method, however, is also inaccurate if the landing position differs substantially from the take-off position. This problem might be solved performing a consecutive double DJ. Thus, the aim of the study is to investigate different DJ variations with respect to reliability.