European journal of applied physiology
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Eur. J. Appl. Physiol. · Dec 2013
Recruitment order of quadriceps motor units: femoral nerve vs. direct quadriceps stimulation.
To investigate potential differences in the recruitment order of motor units (MUs) in the quadriceps femoris when electrical stimulation is applied over the quadriceps belly versus the femoral nerve. ⋯ Femoral nerve stimulation activated MUs according to the size principle, whereas the recruitment order during direct quadriceps stimulation was more complex, depending ultimately on the architecture of the peripheral nerve and its terminal branches below the stimulating electrodes for each muscle. For the VM, MUs were orderly recruited for both stimulation geometries, whereas, for the VL muscle, MUs were orderly recruited for femoral nerve stimulation, but followed no particular order for direct quadriceps stimulation.