Rhythmic arm cycling differentially modulates stretch and H-reflex amplitudes in soleus muscle

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dc.contributor.author Palomino, Andres Felipe
dc.date.accessioned 2011-07-08T18:13:44Z
dc.date.copyright 2011 en_US
dc.date.issued 2011-07-08
dc.identifier.uri http://hdl.handle.net/1828/3401
dc.description.abstract During rhythmic arm cycling soleus H-reflex amplitudes are reduced by modulation of group Ia presynaptic inhibition (Frigon et al, 2004). This reflex suppression is graded with the frequency of arm cycling (Loadman & Zehr 2007; Hundza & Zehr 2009) and 0.8 Hz is the minimum frequency to significantly reduce the soleus H-reflex (Hundza & Zehr 2009). Despite the data on modulation of the soleus H-reflex amplitude induced by rhythmic arm cycling, comparatively little is known about the modulation of stretch reflexes due to remote limb movement. Therefore, the present study was intended to explore the effect of arm cycling on stretch and H-reflex amplitudes in the soleus muscle. In so doing, additional information on the mechanism of action during rhythmic arm cycling would be revealed. Although both reflexes share the same afferent pathway, we hypothesized that stretch reflex amplitudes would be less suppressed by arm cycling because they are less inhibited by presynaptic inhibition (Morita et al, 1998). Failure to reject this hypothesis would add additional strength to the argument that Ia presynaptic inhibition is the mechanism modulating soleus H-reflex amplitude during rhythmic arm cycling. Participants were seated in a customized chair with feet strapped to footplates. Three motor tasks were performed: static control trials and arm cycling at 1 and 2 Hz. Soleus H-reflexes were evoked using single 1 ms pulses of electrical stimulation delivered to the tibial nerve at the popliteal fossa. A constant M-wave and ~6% MVC activation of soleus was maintained across conditions. Stretch reflexes were evoked using a vibratory shaker (ET-126; Labworks Inc). The shaker was placed over the triceps surae tendon and controlled by a custom written LabView program (single sinusoidal pulse at 100Hz). Results demonstrated that rhythmic arm cycling that was effective for conditioning soleus H-reflexes did not show a suppressive effect on the amplitude of the soleus stretch reflex. We suggest this indicates that stretch reflexes are less sensitive to conditioning by rhythmic arm movement, as compared to H-reflexes, due to the relative insensitivity of Ia presynaptic inhibition. en_US
dc.language English eng
dc.language.iso en en_US
dc.subject Arm cycling en_US
dc.subject stretch en_US
dc.subject H-reflex en_US
dc.subject presynaptic inhibition en_US
dc.title Rhythmic arm cycling differentially modulates stretch and H-reflex amplitudes in soleus muscle en_US
dc.type Thesis en_US
dc.contributor.supervisor Zehr, E. Paul
dc.contributor.supervisor Hundza, Sandra R.
dc.degree.department School of Exercise Science, Physical and Health Education en_US
dc.degree.level Master of Science M.Sc. en_US
dc.rights.temp Available to the World Wide Web en_US
dc.description.scholarlevel Graduate en_US

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