Backward and forward walking use different patterns of phase-dependent modulation of cutaneous reflexes in humans

Abstract

Please be advised that this information was generated on 2018-05-12 and may be subject to change.Journal o r N eu ro ph y sio lo g y Vol. 76, No. I. July 1996. Printed in U.S.A. 1 . The phase-dependent modulation of medium-latency (P2) (70-80 ms) responses in semitendinosus (ST), biceps femoris (BF), rectus femoris (RF), and tibialis anterior (TA) was studied with the use of low-intensity stimulation (2 times perception threshold) of the sural nerve. The shocks were given in a random order at 16 phases of the step cycle in 10 normal subjects during forward walking (FW) or backward walking (BW) on a treadmill. Backward and Forward Walking Use Different Patterns of PhaseDependent Modulation of Cutaneous Reflexes in Humans2. All subjects exhibited P2 responses in all muscles studied both during BW and FW. The amplitude of the facilitatory P2 responses showed phase-dependent changes that could not have been predicted on the basis of the variations in background activity throughout the step cycle.5. During FW, the P2 facilitatory responses in BF were large (with respect to the background activity) throughout the whole step cycle except for a short period near the end of the swing phase. In ST the responses were smaller and appeared primarily at the end of the stance phase and during the first part of the swing phase. During the second half of swing the P2 responses were basically suppressive. A modulation pattern similar to the one in ST was found in RF and TA, except that there was no reversal to suppressive responses in the swing phase in RF. Instead, a reduc tion in the amplitude of the facilitatory P2 responses occurred.4. During BW, the modulation pattern recorded in the same subjects was different from the one seen during FW. Large facilita tory P2 responses were present in all muscles in middle and late swing. In the first half of stance the responses were most promi nently seen in BF and RF. At the end of stance and/or at the onset of swing the facilitatory responses decreased in amplitude (BF and RF) or reversed to P2 suppressions (ST and TA).5. We conclude that there are both facilitatory and suppressive pathways from the sural nerve to the leg muscles studied and that the balance of activity in these paths is phase dependent during both FW and BW. It is suggested that the phase-dependent modula tion of P2 responses could largely rely on a central motor program. During BW the same motor program is used as during FW, but possibly running in reverse, thereby causing a shift both in the timing of the reflex reversal and in the periods of reflex suppression.

Flexion Reflex Can Interrupt and Reset the Swimming Rhythm

“…This finding adds to previous evidence of phase-dependent effects of flexion reflex stimuli during forward and backward walking rhythms, especially from studies of cats and humans (Forssberg et al, 1975(Forssberg et al, , 1977Andersson et al, 1978;Schomburg et al, 1978;Forssberg, 1979;Wand et al, 1980;Crenna and Frigo, 1984;Buford and Smith, 1990;Duysens et al, 1990;Duysens et al, 1992;Duysens et al, 1996;Degtyarenko et al, 1998;Burke, 1999;Ménard et al, 1999;Perreault et al, 1999;McCrea, 2001;Spaich et al, 2004;Quevedo et al, 2005;Sandrini et al, 2005;Hultborn, 2006;Knikou et al, 2006;Knikou, 2007;Knikou et al, 2009;Duysens et al, 2013) and during swimming (Lennard, 1985) and all three forms of scratching rhythms in turtles (Currie and Stein, 1989). Collectively, these findings suggest that leg flexion reflex (as well as other leg reflexes) are modulated or gated according to hip phase for multiple forms of locomotion and scratching in limbed vertebrates generally.…”

Biceps femoris tendon jerk reflexes are enhanced at the end of the swing phase in humans

“…The present results show that the amplitude o f the BF tendon jerk reflex is at a maximum near the end of the swing phase, in a period when this muscle is normally very active both during 'reduced' (this study) and normal walk ing [5]. This finding lends support to the hypothesis that activation of this muscle at end swing is at least partly generated through stretch reflexes [7].…”

“…Furthermore, the data illustrate that during this critical period, just prior to foot placement, there is a highly differentiated control of : and reflex pathways. In contrast to cutaneous reflexes in BF which are suppressed in this phase during walking [5], sensibility to cutaneous stimuli are at a maxi mum (subjective judgments of intensity; [4]). Similarly, the BF stretch reflexes are then largest.…”

“…The hammer was : of the driven by a revolving field magnetic motor whole apparatus 950 g; power 120 W) fixed to the back of lower left leg. The hammer was accelerated by the •mg is known that the part of the swing phase during walking [5]. If the same is true for stretch reflexes then it is unlikely that the BF activation at end swing is reflexly generated.…”

Neural control of locomotion; Part 1: The central pattern generator from cats to humans

“…Winter et al (1989) suggested that " backward walking is almost a simple reversal of forward walking" [95]. Duysens et al (1996) studied the regulation of the gain of cutaneous reflex pathways during BW [96], The hypothesis was that if BW walking in humans is pro duced by a forward motor program, reversed in se quence, then the phase-dependent modulation pattern of cutaneous reflexes should be reversed in sequence during BW. At one of the 16 different phases of the step cycle an electrical stimulus train was applied over the sural nerve at two perception threshold (PT) both during FW and BW and unpredictable for the subject.…”