Unilateral stiffness interventions augment vertical stiffness and change of direction speed

It has previously been shown that pre-conditioning interventions can augment change of direction speed (CODS). However, the mechanistic nature of these augmentations has not been well considered. The current study sought to determine the effects of pre-conditioning interventions designed to augment vertical stiffness on CODS. Following familiarization, ten healthy males (age: 22 ± 2 years; height: 1.78 ± 0.05 m; body mass: 75.1 ± 8.7 kg) performed three different stiffness interventions in a randomized and counterbalanced order. The interventions were: a) bilateral-focused, b) unilateral-focused, and c) a control of CODS test practice. Vertical stiffness and joint stiffness was determined pre- and post-intervention using a single leg drop jump task. CODS test performance was assessed post-intervention using a double 90o cutting task. Performances following the unilateral intervention were significantly faster than control (1.7%; P = 0.011; d = -1.08), but not significantly faster than the bilateral intervention (1.0% faster; P = 0.14; d = -0.59). Versus control, vertical stiffness was 14% greater (P = 0.049; d = 0.39) following the unilateral intervention and 11% greater (P = 0.019; d = 0.31) following the bilateral intervention; there was no difference between unilateral and bilateral interventions (P = 0.94; d = -0.08). The findings of the current study suggest that unilateral pre-conditioning interventions designed to augment vertical stiffness improve CODS within this experimental cohort.