Differences in the vertical and horizontal force-velocity profile between academy and senior professional rugby league players, and the implications for strength and speed training.

BACKGROUND: This study compared the vertical and horizontal force-velocity (FV) profile of academy and senior rugby league players. METHODS: Nineteen senior and twenty academy players from one professional club participated in this study. The vertical FV profile was determined using a series of loaded squat jumps (0.4 to 80 kg) with jump height recorded. The horizontal FV profile involved a 30-m over-ground sprint with split times recorded at 5, 10, 15, 20 and 30 m. Theoretical maximal force (F0), velocity (V0) and power (Pmax), optimal F0 and V0, and activity specific variables (e.g., vertical FV imbalance) were determined. RESULTS: Absolute F0 and Pmax from the vertical and horizontal profile were moderately different between groups (standardized mean difference [SMD] = 0.64-1.20, P<0.001-0.026), whilst for V0, differences were small (SMD=0.33-0.41, P=0.149-0.283). Differences in relative F0, Pmax and optimal F0 during both assessments were trivial to moderate (SMD=0.03-0.82, P=0.021-0.907). CONCLUSIONS: These results demonstrate senior and academy players present with different FV profiles and highlight some potential developmental opportunities for senior and academy rugby league players that sport scientists, strength and conditioning and rugby coaches can implement when designing programmes and considering long-term athlete development.