Rhythmic arm cycling produces a non-specific signal that suppresses Soleus H-reflex amplitude in stationary legs

Abstract

Rhythmic arm cycling significantly suppresses Hoffmann (H-) reflex amplitude in Soleus muscles of stationary legs. The specific parameters of arm cycling contributing to this suppression, however, are unknown. Between the arms or legs, movement results in suppression of the H-reflex that is specifically related to the phase of movement and the locus of limb movement. We speculated that the effects of arm movement features on H-reflexes in the leg would be similar and hypothesized that the Soleus H-reflex suppression evoked by arm movement would therefore be specifically related to: (1) phase of the movement; (2) the locus of the movement (i.e., ipsilateral or contralateral arm); (3) range of arm motion; and (4) frequency of arm cycling. Participants performed bilateral arm cycling at 1 and 2 Hz with short and long-crank lengths. Ipsilateral and contralateral arm cycling was also performed at 1 Hz with a long-crank length. Soleus H-reflexes were evoked at four equidistant phases and comparisons were made while maintaining similar evoked motor waves and Soleus activation. Our results show that comparable suppressive effects were seen at all phases of the arm movement: there was no phase-dependence. Further, bilateral or unilateral (whether ipsi- or contralateral arm) cycling yielded equivalent suppression of the H-reflex amplitude. Cycling at 2 Hz resulted in a significantly larger suppression than with 1 Hz cycling. We conclude that a general, rather than a specific, signal related to the command to produce rhythmic arm muscle activity mediates the suppression of Soleus H-reflex during arm cycling.

The effect of immobilization of the head and trunk on arm-cycling-induced depression of soleus motoneuron pool excitability

“…This finding confirmed previous findings that the soleus H-reflexes were not phase-dependently modulated during cyclic movement of the arm (Frigon et al 2004;Loadman and Zehr 2007). However, other previous studies indicate that interlimb neural communication is phase-dependently modulated during rhythmic movement.…”

“…Oscillatory movement of the foot modulated H-reflex excitability in the forearm muscle (Baldissera et al 2002;Cerri et al 2003;Borroni et al 2004). The H-reflex in the soleus muscle, an ankle extensor, was depressed during rhythmic arm cycling (Frigon et al 2004;Loadman and Zehr 2007;Dragert and Zehr 2009;Hundza and Zehr 2009) and during rhythmic arm swing (Hiraoka 2001;Hiraoka and Iwata 2006).…”

“…The head and trunk were immobilized in previous studies in which rhythmic arm-swinginduced depression of the soleus H-reflex was investigated (Hiraoka 2001;Hiraoka and Iwata 2006), but in several studies investigating cyclic arm-movement-induced depression of the soleus H-reflex, only the trunk was immobilized (Frigon et al 2004;Loadman and Zehr 2007;Dragert and Zehr 2009;Hundza and Zehr 2009).…”

Neural control of rhythmic arm cycling after stroke

“…Understanding the status of the nervous system function after stroke is crucial in advancing effective rehabilitative practice. We previously showed that rhythmic arm cycling can activate descending pathways to modulate lumbar spinal cord activity (Dragert and Zehr 2009;Frigon et al 2004;Hundza and Zehr 2009;Loadman and Zehr 2007;Zehr et al 2004b). Recently this observation was extended to stroke participants where a similar but reduced effect was observed even in those with spasticity (Barzi and Zehr 2008).…”

Long-Term Plasticity in Reflex Excitability Induced by Five Weeks of Arm and Leg Cycling Training after Stroke

“…In addition, phase-dependent modulation found in muscles of all four limbs during rhythmic movement is suggestive of coupling between segmental spinal networks [12,13,14,15,16]. Regulation of rhythmic arm and leg movement is supported by somatosensory linkages in the form of interlimb reflexes [12,17,18] and neural coupling between lumbar and cervical spinal cord networks [10,19,20,21,22]. …”