Introduction: The purpose of this study was to investigate the relative activation of vastus medialis (VM) and vastus lateralis (VL) muscles during voluntary and stimulated isometric contractions at different joint angles.
Methods: Sixteen healthy men (mean age: 26 years) completed maximal voluntary and stimulated contractions of the knee extensor muscles at 30°, 65°, and 100° of knee flexion. VM/VL ratios were calculated from voluntary electromyographic (EMG) and evoked torque recordings.
Results: Both EMG and VM/VL torque ratios were significantly lower at 30° than at 100° of knee flexion (P < 0.05).
Conclusions: These results can be explained by the relatively small contribution of the VM muscle to knee extension torque at short muscle length. Such disadvantage of the VM muscle at extended knee positions does not seem to be compensated by an increased neural drive. Muscle Nerve 56: 968-974, 2017.
Keywords: electrical stimulation; electromyography; knee angle; neural activation; quadriceps; twitch torque.
© 2016 Wiley Periodicals, Inc.