Difference in Dynamic Body Balance between Forward and Lateral Single-Leg Hop Landing

Since the loss of balance can result in falls or lower extremity injuries during sports or daily activities, quantitative evaluation of one’s ability to maintain balance with changes in the direction of motion is crucial. The present study aimed to assess whether the trajectory length of the center of pressure (COP) and peak values of the ground reaction force (GRF) following a single-leg hop landing differ when hopping forward or laterally, and to ascertain disparities in balance characteristics due to differences in hop direction. Twenty-four young volunteers (mean age, 22.1 years) were asked to stand on one foot on a level floor, take a half step in the forward and lateral directions, and land on one foot, repeating this task ten times on each leg. Data measured in this study included COP trajectory length up to 200 ms (200msCOP) and 1 s (1sCOP), the peak value of the frontal GRF (pF_ML), the peak value of the sagittal GRF (pF_AP), and the peak value of the vertical GRF (pF_V). Means were calculated from the measured values of ten attempts. 200msCOP reflects postural sway immediately after landing, and pF_ML and pF_V reflect the force of impact upon landing. 200msCOP, pF_ML, and pF_V were significantly higher with lateral hopping versus forward hopping (p<0.01, p<0.05, and p<0.05), and hop direction yielded differences in dynamic balance.