Spinal and supraspinal mechanisms affecting torque development at different joint angles

: We examined the neural mechanisms responsible for plantar flexion torque changes at different joint positions. Methods : Nine subjects performed maximal voluntary contractions (MVC) at 6 ankle–knee angle combinations [3 ankle angles (dorsiflexion, anatomic position, plantar flexion) and 2 knee angles (flexion, full extension)]. Neural mechanisms were determined by V‐wave, H‐reflex (at rest and during MVC), and electromyography during MVC (RMS), normalized to the muscle compound action potential (V/M sup , H max /M max , H sup /M sup and RMS/M sup ) and voluntary activation (VA), while muscle function was assessed by doublet amplitude. Results : MVC and doublet amplitude were significantly lower at plantar flexion ( P < 0.01), while VA was significantly lower at dorsiflexion and full knee extension ( P < 0.05). V/M sup and RMS/M sup were significantly lower at knee extension ( P < 0.01), while H sup /M sup was not affected by joint angle. Conclusions : These results indicate that joint positions leading to muscle lengthening produce reduced neural drive, due mainly to supraspinal mechanisms. Muscle Nerve 53 : 626–632, 2016