The reflexive control of knee stability during movement

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Kocer, Muhammet Berkan
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Stimulation of the common peroneal nerve (CPN) excites quadriceps (Q) motoneurons, and it is called the CPQ reflex. It has been suggested that the CPQ reflex assists in ground reaction force (GRF) generation during walking when conditions require that, for example, at most commonly used walking speeds or on an incline. This reflex is evoked by neurons in a spinal pathway relaying sensory input from muscle afferents and descending locomotor commands. The CPQ reflex pathway is thought to coordinate sensory input with ongoing motor activity. The aim here was to evaluate the effects of the walking speed of the stimulated leg on the CPQ reflex. The hypothesis that increased speed on one side will reduce the CPQ was tested. Neurologically intact, generally healthy participants (n=12) in the 20-48 years old age range were evaluated under different treadmill walking conditions: both legs walking at the same speed (BLW) or legs walking with different speeds at a ratio 1 to 1.25 (R1.25), 1 to 1.5 (R1.5) and 1 to 2 (R2) so that the right (R) belt speed was increased, and the left belt was kept constant. EMG responses in lower leg muscles were compared in steps with and without stimulation of the CPN at an optimal window after the R heel strike. Our result showed that as speed increased on the R side, the size of the R CPQ reflex showed a tendency to decrease but no significant changes were found, likely due to our sample size (n=5). To understand the factors that may influence the CPQ reflex, the effect of walking speed under the stimulated side on ground reaction forces (GRFs), the stance and swing time and the left-right asymmetry were also examined. Increasing speed amplified the peaks of the anterior-posterior and vertical components of GRFs. We also found that R CPN stimulation altered the left-right asymmetry of the propulsive peak of the GRFs. The findings of this study are important for a better understanding of the CPQ reflex and for using CPN stimulation in clinical settings to improve knee stability during walking.
CPQ, GRFs, Motor Control, CPN