Group II muscle afferents probably contribute to the medium latency soleus stretch reflex during walking in humans

Abstract

The central nervous system (CNS) takes advantage of a network of complex neural pathways and mechanisms in the control of normal human gait. One such mechanism is the use of afferent feedback from muscle, cutaneous and joint receptors. Our knowledge of the contribution of afferent information in human gait is still limited, although this has been an area of active research for many years (e.g. Dietz et al. 1985;Yang et al. 1991;Sinkjaer et al. 1996). Yang et al. (1991) and Sinkjaer et al. (1996) have shown that afferent-mediated feedback is used by the CNS in the control of gait when an unexpected stretch of the ankle extensors is imposed. More recently, Sinkjaer et al. (2000) provided evidence that during walking, up to 50 % of the background EMG from the soleus muscle can be attributed to afferent feedback. However, the relative importance of the separate afferent pathways may differ for the background locomotor EMG and the EMG that results from an imposed stretch.When the human soleus muscle is stretched in a seated subject, two distinct bursts, with average peak latencies of 59 and 86 ms are evident in the EMG (Toft et al. 1989). These bursts are often referred to as the short (SLR) and medium (MLR) reflex responses, respectively, and have also been labelled the M1 and M2 stretch reflex responses, respectively. The short latency response has an onset latency of approximately 40 ms and is attributed to monosynaptic excitation of spinal motoneurones from the large diameter group Ia afferent fibres (Taylor et al.Group II muscle afferents probably contribute to the medium latency soleus stretch reflex during walking in humans 1. The objective of this study was to determine which afferents contribute to the medium latency response of the soleus stretch reflex resulting from an unexpected perturbation during human walking.2. Fourteen healthy subjects walked on a treadmill at approximately 3.5 km h _1 with the left ankle attached to a portable stretching device. The soleus stretch reflex was elicited by applying small amplitude (~8 deg) dorsiflexion perturbations 200 ms after heel contact.3. Short and medium latency responses were observed with latencies of 55 ± 5 and 78 ± 6 ms, respectively. The short latency response was velocity sensitive (P < 0.001), while the medium latency response was not (P = 0.725).4. Nerve cooling increased the delay of the medium latency component to a greater extent than that of the short latency component (P < 0.005).5. Ischaemia strongly decreased the short latency component (P = 0.004), whereas the medium latency component was unchanged (P = 0.437).6. Two hours after the ingestion of tizanidine, an a 2 -adrenergic receptor agonist known to selectively depress the transmission in the group II afferent pathway, the medium latency reflex was strongly depressed (P = 0.007), whereas the short latency component was unchanged (P = 0.653).7. An ankle block with lidocaine hydrochloride was performed to suppress the cutaneous afferents of the foot and ankle. Neither the short (P = 0.453) nor m...

Interlimb relation during the double support phase of gait: An electromyographic, mechanical and energy-based analysis

“…In fact, experiments on interlimb coordination of leg muscle activation have confirmed that unilateral leg displacement during gait evokes a bilateral response pattern, with a similar onset in both sides 3,4 but only when both limbs are performing a supportive role 5,6 . This is consistent with the evidence that a large majority of midlumbar interneurones recipient from group II input are influenced by afferent fibres from both ipsilateral and contralateral sides 7 and by vestibulo-and reticulo-spinal pathways 8 , and with the importance given to medium latency response from group II to feedback in the stance phase of gait 9 .…”

Differential effects of stimulus characteristics during knee joint perturbation on hamstring and quadriceps reflex responses

“…These findings correspond to the results of Grey and coworkers, who reported the SLR of the ankle muscle soleus being velocity sensitive while the MLR was not (Grey et al, 2001). These previous results, which were achieved during perturbation of gait, have been confirmed in isolated rotational perturbation of the ankle joint in an ergometer (Gollhofer & Rapp, 1993;Leukel et al, 2009).…”

“…For the ankle joint, it was shown that latency and magnitude of reflex responses are determined by the stretch velocity and the amplitude. For instance, the short latency response (SLR) of the soleus muscle which is considered to be mediated by fast conducting Ia afferent fibers (Bove, Nardone, & Schieppati, 2003;Morin & Pierrot-Deseilligny, 1977), was reported to be sensitive to the stimulus velocity (Gollhofer & Rapp, 1993;Grey, Ladouceur, Andersen, Nielsen, & Sinkjaer, 2001;Leukel et al, 2009). The size of the medium latency response (MLR), on the other hand, was determined by the amplitude of the induced stretch (Gollhofer & Rapp, 1993;Leukel et al, 2009).…”

“…The size of the medium latency response (MLR), on the other hand, was determined by the amplitude of the induced stretch (Gollhofer & Rapp, 1993;Leukel et al, 2009). The MLR has been attributed to oligosynaptic excitation of spinal motoneurons via group II afferents (Bove et al, 2003;Grey et al, 2001;Nardone & Schieppati, 1998;Nardone & Schieppati, 2004) and possibly by group Ib afferents (Dietz & Duysens, 2000).…”

Speed adaptation in a powered transtibial prosthesis controlled with a neuromuscular model

“…If the muscle is lengthening too rapidly, the velocity term will increase the activation; if it is shortening too quickly, the velocity term will reduce activation. Several empirical studies [12,[34][35][36][37][38] have demonstrated the presence of afferent feedback in the plantar flexors during stance. These studies record the changes in muscle EMG signals when the gait of a subject is perturbed either by changing the inclination of the walking surface or by forcing muscle-tendon length changes using an orthosis.…”