Effects of Drop-height and Surface Instability on Jump Performance and Knee Kinematics

Abstract

The purpose of this study was to examine the combined effects of drop-height and surface condition on drop jump (DJ) performance and knee joint kinematics. DJ performance, sagittal and frontal plane knee joint kinematics were measured in jump experienced young male and female adults during DJs on stable, unstable and highly unstable surfaces using different drop-heights (20, 40, 60 cm). Findings revealed impaired DJ performance (Δ5-16%; p<0.05; 1.43≤d≤2.82), reduced knee valgus motion (Δ33-52%; p<0.001; 2.70≤d≤3.59), and larger maximum knee flexion angles (Δ13-19%; p<0.01; 1.74≤d≤1.75) when using higher (60 cm) compared to lower drop-heights (≤40 cm). Further, lower knee flexion angles and velocity were found (Δ8-16%; p<0.01; 1.49≤d≤2.38) with increasing surface instability. When performing DJs from high (60 cm) compared to moderate drop-heights (40 cm) on highly unstable surfaces, higher knee flexion velocity and maximum knee valgus angles were found (Δ15-19%; p<0.01; 1.50≤d≤1.53). No significant main and/or interaction effects were observed for the factor sex. In conclusion, knee motion strategies were modified by the factors 'drop-height' and/or 'surface instability'. The combination of high drop-heights (>40 cm) together with highly unstable surfaces should be used cautiously during plyometrics because this may increase the risk of injury due to higher knee valgus stress.

Effects of Relative Drop Heights of Drop Jump Biomechanics in Male Volleyball Players

“…Therefore, 100 %CMJH may be the turning point for any observed biomechanical changes in the relative drop heights for DJ plyometric training intensity. These findings were similar to previous investigations from absolute drop heights that reported both rapid and powerful DJ performance increased from 35- [37] and 40-cm [38,39] and reported those as the turning point compared to greater heights. Larger drop heights may lead to decrements of DJ performances due to a reduction from the SSC, which might be a protective strategy for preventing muscle and tendon injury associated with a higher impact GRF [8,9,19].…”

“…The DJ performance remained unchanged with incremental drop heights in the current study, which agreed with Bassa et al [40] and Bencke et al [41] but contrasted with Prieske et al [37], Andrade et al [38] and Lesinski et al [39]. Prieske et al [37] reported that both the DJH and RSI increased with drop heights from 20-to 50-cm and from 20-to 35-cm, respectively, in 239 adolescent handball players, irrespective of sex.…”

“…Further, they showed that the 50-cm drop-height induced additional increments to the DJH but at the expense of ground contact time, therefore, reducing RSI. Andrade et al [38] and Lesinski et al [39] reported using a drop height of 40-cm resulted in the greatest RSI. The discrepancy in these findings may be attributed to the number of participants, biodiversity of participants and their DJ technique between investigations.…”

A systematic review on the effects of resistance and plyometric training on physical fitness in youth- What do comparative studies tell us?

“…However, training surface (i.e., soft versus hard surfaces) has to be taken into account and might affect training-related outcomes as well. Studies with adults have shown that plyometric exercises performed under unstable conditions can result in performance decrements [ 135 ] and altered kinematic responses (joint range of movement) compared to plyometrics under stable conditions [ 136 , 137 ]. Research comparing plyometrics on stable versus unstable surface in children and adolescents showed mixed results [ 85 – 87 ].…”

Anticipation modulates neuromechanics of drop jumps in known or unknown ground stiffness

“…Within conditions were the SGS is known, variation in SGS is associated with changes in peak force [11], jump height [10,11], ground contact time [10,11] and joint kinematics [11,12,17,18]. Concomitantly, adaptations in muscle pre-activation prior to ground contact [11,12,19] and subsequent concentric phase have been reported [11,13].…”