Electromyography and Kinematic Analysis of Lower Limb Function During Standardized Bodyweight Squats in Individuals with Flexible Flat Foot

Document Type : Original Article

Authors
Pouria Tangsiri
Farideh Babakhani
Ramin Balouchi
Mohammadreza Hatefi
Naser Ebrahimi
Department of Sport Injuries and Corrective Exercises, Faculty of Physical Education and Sport Science, Allameh Tabataba’i University, Tehran, Iran
10.48311/ijmpp.2025.117722.82908
Abstract
Aims: This study explores  the effects of Flexible Flat Foot (FFF) on movement stability and muscle activation patterns during bodyweight squats. Since flat foot alters biomechanics and squats are essential for strength and injury prevention, their interaction is studied to improve rehabilitation and training interventions.
Method and Materials: In this study24 university amateur male athletes (12 with Flexible Flat Foot FFF, 12 healthy; age 18–28 years, ≥3 weekly strength training sessions) performed bodyweight squats to 90° knee flexion. Participants were classified into the FFF group based on a navicular drop of ≥10 mm during weight bearing, as measured by the Navicular Drop Test. Electromyography (EMG) of Tibialis Anterior (TA), GastrocNemius (GN), Vastus Medialis Oblique (VMO), Gluteus Maximus (Gmax), and Quadratus Lumborum (Ql), along with kinematic analysis of ankle, knee, hip, and pelvis, were measured within the 0–90° knee flexion range. Comparisons between groups were made for eccentric and concentric phases.
Findings: Compared with controls, the FFF group showed significantly reduced activation of the Vastus Medialis Oblique (VMO) (eccentric: P = 0.023; concentric: P = 0.026) and (TA (eccentric: P = 0.001). Conversely, Gmax activity was higher in both phases (eccentric: P = 0.001; concentric: P = 0.041). Kinematic analysis also showed reduced flexion angles at the hip, knee, and ankle joints during the eccentric phase (P = 0.025, P = 0.055, P = 0.025, respectively). Pelvic abduction–adduction range of motion increased significantly in the concentric phase (P = 0.037), while non-significant decreases were observed in hip, knee, and ankle extension ROM (P = 0.055).
Conclusion: : This study demonstrated that individuals with flexible flatfoot exhibit altered muscle activation patterns (reduced VMO and TA activity, elevated Gmax activity) and restricted joint kinematics (reduced flexion-extension at the femur, knee, and ankle) during bodyweight squats compared to individuals with normal arches. These findings highlight a distinct biomechanical profile associated with flexible flatfoot during a fundamental closed-kinetic-chain exercise. They underscore the importance of considering foot posture when assessing squatting mechanics. Future rehabilitation or training protocols for this population may benefit from addressing these specific neuromuscular and kinematic alterations. Further research is warranted to investigate the longitudinal development and potential clinical implications of these biomechanical differences.

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International Journal of Musculoskeletal Pain Prevention
Volume 11, Issue 1
Winter 2026
Pages 1363-1372