Is there any biomechanical justification to use hopping as a return to running test? A cross-sectional study.

OBJECTIVE:To assess the agreement and the correlation between asymmetry indexes of leg stiffness (AI(Kleg)) in running and hopping and the correlation between leg stiffness (Kleg) in running and hopping. DESIGN:Cross-sectional study. SETTING:Clinical facility. PARTICIPANTS:Twelve healthy runners (5 women and 7 men; mean (SD) age = 36.6 (10.1) years; activity level = 6.4 (0.9) on Tegner scale). MAIN OUTCOME MEASURES:A treadmill instrumented by photoelectric cells was used to collect data (flight and contact times) during running assessment (preferential and imposed velocity (3.33 m s-1) and during a hopping test. Kleg and AI(Kleg) were computed for each modality. Correlation tests were performed, and Bland Altman's plot was created. RESULTS:A significant and large correlation was found between Kleg in hopping and running at imposed speed (r = 0.6, p = 0.001). An acceptable agreement was found between the AIs in hopping and running, with a bias of 0.04 (-0.15-0.06) at imposed speed and 0.03 (-0.13-0.07) at preferred speed. CONCLUSION:Our results suggest that testing an athlete for asymmetry in hopping might help to understand what happens in running. For this purpose, further research is needed, especially in an injured population, to better understand the association between biomechanical asymmetry in hopping and running.