Gastrocnemius inflexibility on foot progression angle and ankle kinetics during walking

Background Gastrocnemius inflexibility is a major problem in many orthopedic and neurological patients. Clinically, inflexible gastrocnemius muscles interfere with the performance of functional abilities and associate with many overuse injuries of the lower extremity. The purpose of this study was to investigate the effects of the gastrocnemius inflexibility on the foot progression angle and ankle kinetics during walking. Methods There were 50 subjects, 23 patients with the inflexible gastrocnemius and 27 normal subjects, included in this investigation. Participants were asked to walk at two preset cadences of 100 steps/min and 140 steps/min. Data were collected from a motion analysis system and force plates. Kinematic and kinetic variables of gait were computed and analyzed. Findings Compared with the control group, greater toe-out foot progression angle (P = 0.001, effect size = 0.314) and knee external rotation (P = 0.008, effect size = 0.136) were found in the inflexible group during stance phase. Furthermore, significant greater plantarflexion moment (P = 0.032, effect size = 0.093) and medial ground reaction force (P = 0.009, effect size = 0.135) during midstance were discovered in the inflexible group. Interpretation The present results indicate that gastrocnemius inflexibility might bring about the changes in the joint angles, ankle moments and ground reaction forces. The abnormal joint alignment in the lower extremities and greater force upon joint tissue might be significant for the clinical considerations on soft tissue injuries for the patients with inflexible gastrocnemius muscles.