Absence of Reciprocal Inhibition in Control of Walking in Man

In control swing phase hamstrings activation began mid-swing approx 70 ms before quadriceps activation. Activity in hamstrings ceased 180 ms after quadriceps activation. In the resistance swing a momentary unexpected resistance was applied during swing (Garrett et al, 1985). Analysis of variance showed a significance advance (P<0.01) in the onset of quadriceps activation following resistance. Reflex nature of this quadriceps contraction is more likely to be associated with reciprocal inhibition of the antagonist knee flexor (hamstrings). Nevertheless no significant correlation was observed between quadriceps activation and cessation of hamstrings activity in either control swing (r=0.26) or resistance swing (r=0.04). The modest correlation observed between onset of activation in knee extensor (quadriceps) and knee flexor (hamstrings) in control (r=0.44) and resistance (r=0.53) suggest a trend towards co-contraction.