Inhibition of short latency reflex linking the pretibial muscles to quadriceps motoneurones during stance to swing transition in humans

The modulation of short latency reflex linking the pretibial to quadriceps muscle [CPQ reflex] was investigated in seven subjects during walking on a treadmill at the stance to swing transition period. The intensity of quadriceps [Q] EMG was increased throughout the gait cycle by using a modified knee orthosis. Pairs of spring were added to the orthosis to produce different levels of .muscular activity in Q during the midstance, transition period and terminal swing phase of gait. Electrical stimulation was applied to the common peroneal nerve [CRN] at these three instants of gait. The peak to peak amplitude of CPQ reflex was significantly increased with escalation of background EMG in Q during midstance [p<0.015] and terminal swing [p<0.04]. At the transition period however, despite significant increase in the Q activity no responses was evoked. The results were indicative of an active inhibition of the reflex pathway during transition period. This inhibition could help the unloading of the limb that is necessary for the initiation of the swing phase

gain modulation of the heteronymous excitation of quadriceps with changes in position of the knee and hip joints in humans

A potent heteronymous excitation of quadriceps motoneurones via common peroneal group I and II afferents has been demonstrated in normal subjects. The aim of this study was to establish the contribution of knee and hip proprioceptors on the modulation of this biphasic facilitation. Single 0.2ms pulses were delivered to common peroneal nerve at the intensity of 2xmotor threshold in tibialis anterior. The peak to peak amplitude and area of the excitatory responses were measured in ongoing EMG of voluntarily contracted rectus femoris at different knee and hip joint positions. The reflex showed a significant inhibition with the knee flexion [P<0.0001] and hip extension [P<0.01]. It was concluded that coordinate activation of ankle flexors and knee extensors could modulated by the knee and hip joints proprioceptors