Entrainment of vastus medialis complex activity differs between genders.

INTRODUCTION That the vastus medialis oblique (VMO) is a functional unit of the vastus medialis (VM) is disputed. Delayed VMO activation predicts patellofemoral pain, which has higher rates in women. METHODS Single MUs and surface electromyogram (EMG) were collected from the VMO and VM of 9 men and 9 women. Men were tested once; women were tested during 5 menstrual phases. Coherence was assessed for motor unit (MU) firings within and between the VM and VMO using multilevel logistic models to determine statistical significance. RESULTS Compared with women, men have 741% (MU pairs) and 256% (MU-EMG pairs) greater odds of common drive (0-5 Hz) coherent oscillations. MU pairs from the VMO and the dual VM/VMO complex have 228% and 212% greater odds of coherent oscillations in the beta band (15-35 Hz) compared with VM pairs. CONCLUSIONS The VM and VMO are neurologically different muscles; control of the VM complex is sexually dimorphic.