Does Symmetry in Ground Reaction Force Represent Symmetry in Knee Loading Patterns during Landing from a Lateral-moving Jump?

Asymmetrical lower limb loading during landing may lead to overuse knee injuries if one limb is required to repetitively attenuate greater load. Symmetry of the peak vertical ground reaction force (vGRF) and knee moment generated in the lead and trail lower limbs of healthy female volleyball players during landing from a lateral-moving jump were determined. Each participant performed five jump-landings moving left and moving right onto two force platforms (1500 Hz). Peak vGRF (BW) and peak knee extensor moments (Nm/kg) were obtained and analysed. A symmetry index was used to calculate the functional symmetry of knee loading patterns during landing. No significant between-limb differences in the vGRF or knee moment magnitude were observed. However, functional asymmetry was identified and appeared to be influenced by movement direction. When players moved right, there was an average asymmetry of 18.1% and 16.1% for the vGRF and knee moment, respectively. This suggests that the dominant (lead) limb attenuates more load than the non-dominant (trail) limb. Based on these results we recommend that when investigating the magnitude of the vGRF or knee extensor moment generated during landing, one force platform is sufficient. However, dual force platforms are recommended when conducting injury prevention research.