Altered kinematics and muscle activities during half squats in people with ankle sprain history.

Copers are individuals with a history of ankle sprain who return to daily and sports activities without recurrent instability. However, it is unclear whether copers can use movement strategies comparable to those of healthy individuals without a history of ankle sprain. Understanding these movement strategies may be important for designing effective training programs and avoiding unintended biomechanical adaptations. Therefore, we aimed to compare the kinematics and muscular activities of the lower limbs during half squats and gait between copers and healthy controls. Ten copers (3 females) and 10 controls (4 females) were included in this secondary cross-sectional study. All participants were young, physically active adults who engaged in recreational physical activities for more than 1.5 h per week. We compared mean and peak angles of the thigh, shank, and foot calculated from inertial measurement units, as well as muscle activities of the biceps femoris long head, rectus femoris, gastrocnemius, and tibialis anterior between copers and controls during half squats and gait. During the half squat, copers exhibited lower thigh rotational angles and lower activities of biceps femoris long head, rectus femoris and tibialis anterior across both the descending and ascending phases, accompanied by a higher mean foot angle. In contrast, gait-related group differences were limited to the mean shank angle during the stance phase, with no significant differences observed in other limb angles or muscle activities. These findings suggest that movement strategy alterations in copers are task-dependent and more evident during demanding exercises such as the half squat than during level walking. Identifying such movement characteristics may be important for designing efficient training or rehabilitation programs for individuals with a history of ankle sprain.