[ feed-forward effect of pretibial muscles on quadriceps femoris during stance phase of gait]

ABSTRACT

An excitatory pathway is reported to link the pretibial muscles to quadriceps motoneurones. It has been suggested that the interneurones in this reflex pathway relay the supraspinal inputs to quadriceps motoneurones. This may suggest an important role of this neural pathway in the motor control of knee during activities such as walking. In this regard, the pattern of modulation of this short latency reflex was investigated in normal subjects during walking in order to find its role in the motor control of quadriceps muscles. The reflex was elicited in 12 subjects by stimuli applied to common peroneal nerve at several points of gait cycle during walking on treadmill. The reflex magnitude and the intensity of the contraction were calculated from the surface EMG recorded in vastus medialis, rectus femoris and tibialis anterior and was normalized as the percentage of the maximum voluntary contraction in related muscles. The reflex showed the significant correlation with the intensity of contraction in quadriceps, mainly during the early stance phase. The correlation was weak during transition period from stance to swing, where rectus femoris showed a small peak of activity in half of the subjects and it was not accompanied by any reflex. The average peak activity in tibialis anterior was 69 ms preceded that of quadriceps. The precedence of activity in anterior tibial muscle and the strong presence of the reflex during the early stance phase may indicate a positive feed-forward effect from ankle dorsiflexor afferents to quadriceps muscle. Stimulation and activation of this neural connection may have clinical application in the improvement of the motor control of quadriceps muscles as an antigravity muscle in patients with gait disorders