Fatigue Effects on Single-Leg Squat Kinetics and Kinematics in Athletes with Concurrent Flexible Flatfoot and Genu Varum

Abstract

Background: Athletes with flexible flatfoot and genu varum are at an increased risk of injury. These deformities alter force distribution and joint kinematics and may affect athletic performance. Objectives: This study aimed to compare the effects of fatigue on lower-limb kinetics and kinematics during the single-leg squat (SLS) task between athletes with and without concomitant flexible flatfoot and genu varum deformities. Methods: This study compared male collegiate athletes with concurrent flexible flatfoot and genu varum (n = 10) with athletes without these conditions (n = 8). Single-leg squat (SLS) kinematics and kinetics were recorded using a 10-camera motion-capture system and a force plate. Flatfoot and genu varum were assessed using Brody's method and calipers. To induce fatigue, participants completed a protocol consisting of 10 single-leg squats, 2 maximal vertical jumps, and 20 step-up repetitions. Data were analyzed using analysis of covariance (ANCOVA) (P < 0.05). Results: No significant differences were observed in joint movement patterns or force-related parameters in any anatomical plane between athletes with concurrent flexible flatfoot and genu varum deformities and those without these conditions (P > 0.05). Conclusions: Fatigue affected SLS execution similarly in both groups, with no significant changes observed in lower-limb joint mechanics or movement patterns, even among athletes whose anatomical alignment predisposes them to musculoskeletal injury.