Foot rotation influences the activity of medial and lateral hamstrings during conventional rehabilitation exercises in patients following anterior cruciate ligament reconstruction

Abstract

ObjectivesTo investigate the influence of internal and external foot rotation on medial and lateral hamstring electromyographic (EMG) activity during conventional hamstring exercises in patients following anterior cruciate ligament (ACL) reconstruction. DesignCross-sectional study. SettingEMG activity of medial and lateral hamstrings was recorded during prone leg curl, single-leg bridge and Nordic hamstring exercises with three different foot positions (neutral, internal rotation, external rotation), randomly presented. ParticipantsTwenty patients 9–15 months after ACL reconstruction with the semitendinosus-gracilis graft. Main outcome measuresConcentric and eccentric EMG activity normalized to the EMG activity recorded during a maximal voluntary contraction (MVC). ResultsCompared to the neutral position, the EMG activity of the medial hamstring during prone leg curl exercise was significantly increased by internal foot rotation (concentric: +8.7% MVC; eccentric: +5.9% MVC; p < 0.01; d = 0.88–0.99) and decreased by external rotation (concentric: 5.8% MVC; eccentric: 5.2% MVC; p < 0.05; d = 0.67–0.92). Foot position did not significantly affect hamstring EMG activity during single-leg bridge and Nordic hamstring exercises. ConclusionsActive internal rotation of the foot during prone leg curl exercise can help selectively maximize muscle activity of the medial hamstring portion. This may have implications for post-operative rehabilitation of ACL patients with a semitendinosus-gracilis graft.