Differences in Vertical Performance Caused by Drop Jumping on Surfaces with Different Stiffness

It is well established that muscle activation regulates leg stiffness to optimize stretch shortening cycle (SSC) performance. There is a significant interaction between the surface properties, muscle activation and leg stiffness. The aim of this study was to examine the potentiating adjustments after drop jumps (DJs) executed on two surfaces with different elasticity. Twenty-two adults randomly performed 3 protocols: Protocols with three pre-conditioning DJs performed on a springboard (PSB), Protocol (PG) with three pre-conditioning DJs performed on a stiff ground surface and Protocol without any type of pre-conditioning (C). Vertical jump performance was evaluated at four time points: before (COND0), immediately after pre-conditioning (COND10), and after 1 (COND60) and 2 min (COND120) of rest. Dynamics, kinematics and electromyographic parameters of the ankle were evaluated. ANOVA with repeated measures revealed statistically significant increase in Hpeak, Ppeak and Kleg was observed (p<0.05), over split-intervals and rest periods for Protocol (PSB) while no differences were recorded in jump kinematics. Both protocols (PSB and PG) significantly decreased CI during the pre-activation and eccentric phase, whereas the CI was increased during the concentric phase. The positive effect observed in jump performance could not be attributed to co-activity of the ankle joint, indicating that jumping on an elastic surface, may be beneficial in cases where increased leg stiffness is a determining factor for final performance.