Recurrent inhibition is higher in eccentric compared to isometric and concentric maximal voluntary contractions

Abstract

Together, the current results indicate that recurrent inhibition is elevated for the soleus muscle during eccentric compared to isometric and concentric MVC. Data further suggest that the Renshaw cell activity is specifically controlled by the descending neural drive and/or peripheral neural mechanisms during eccentric MVC.

Autogenic recurrent Renshaw inhibition is elevated in human spinal motor neurones during maximal eccentric muscle contraction in vivo

“…Specifically, when assessing spinal mechanisms responsible for the inability to fully active motor neurones during maximal eccentric muscle actions, reduced evoked H‐reflex responses consistently have been observed for lengthening compared to isometric or shortening contractions performed at both maximal and submaximal effort, indicating suppressed motor neurone excitability and/or an elevated levels of presynaptic or postsynaptic inhibition. As also mentioned by Barrué‐Belou et al, previous study reports suggest that the modulation in corticospinal excitability during eccentric contraction mainly depends on pre‐ and postsynaptic inhibitory mechanisms acting at the spinal level, although the specific nature and relative contribution of these spinal inhibitory mechanisms remain unknown. Moreover, no knowledge exists about the descending control of these spinal pathways from supraspinal centres.…”

“…As stated by Barrué‐Belou et al cortical and spinal neural mechanisms involved in the modulation of the neural drive during eccentric contraction have previously been investigated by comparing the effect of muscle contraction type (i) on the motor evoked potential elicited by transcranial magnetic stimulation (TMS), (ii) on the cervicomedullary motor evoked potential (CMEP) and (iii) on the Hoffmann reflex (H‐reflex, V‐wave) obtained by electrical stimulation of the peripheral motor nerve (for recent reviews, see Duchateau and Enoka, and Aagaard). Specifically, when assessing spinal mechanisms responsible for the inability to fully active motor neurones during maximal eccentric muscle actions, reduced evoked H‐reflex responses consistently have been observed for lengthening compared to isometric or shortening contractions performed at both maximal and submaximal effort, indicating suppressed motor neurone excitability and/or an elevated levels of presynaptic or postsynaptic inhibition.…”

“…More specifically, in their noteworthy study published in this issue of the Acta Physiologica , Barrué‐Belou et al examined the influence of contraction type on the magnitude of autogenic recurrent Renshaw inhibition on spinal motor neurones during maximal voluntary plantarflexor contractions (MVC). Using a sophisticated paired (conditioning) H‐reflex stimulation protocol in the soleus muscle, this study is the first to examine recurrent Renshaw inhibition during eccentric muscle actions in humans.…”

“…Using a sophisticated paired (conditioning) H‐reflex stimulation protocol in the soleus muscle, this study is the first to examine recurrent Renshaw inhibition during eccentric muscle actions in humans. Further and perhaps more notably, Barrué‐Belou et al demonstrate that autogenic recurrent Renshaw inhibition is differently modulated (elevated) during maximal eccentric muscle actions compared to isometric and concentric contractions of maximal voluntary effort. As another significant and novel finding, correlations between H‐reflex amplitude (elicited by submaximal peripheral nerve stimulation) and V‐wave amplitude (maximal nerve stimulation) were observed in their study (their Figure 3), suggesting that significant spinal contribution may exist for the antidromic collision technique utilized by the V‐wave recording, in addition to reflecting the magnitude of descending supraspinal drive to the pool of spinal motor neurones …”

“…The experimental techniques employed by Barrué‐Belou et al are highly innovative and enable the authors to obtain data that in significant ways contribute to expand our current knowledge about the influence of spinal autogenic inhibitory pathways on efferent motor neurone activity during maximal eccentric, concentric and isometric muscle actions. Thus, in their overall conclusion, Barrué‐Belou et al highlight a significant role of recurrent Renshaw inhibition in the modulation of spinal motor neurone excitability (and/or pre‐ and postsynaptic inhibition) during maximal eccentric muscle contraction. As stated by the authors, their data further indicate that Renshaw cell activity is specifically controlled by central descending pathways and/or peripheral mechanisms during eccentric MVC …”