Task- and time-dependent modulation of Ia presynaptic inhibition during fatiguing contractions performed by humans

Baudry, Stéphane; Maerz, Adam H.; Gould, Jeffrey R.; Enoka, Roger M.

doi:10.1152/jn.00954.2010

Cited by 40 publications

(48 citation statements)

References 37 publications

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“…Previous work has shown that the strategies used to sustain force and position control differ during submaximal isometric contractions, even when the net muscle torque is similar across conditions. The rates of change in motor unit activity and modulation of reflex pathways, for example, are more rapid during position control (Baudry et al 2011;Mottram et al 2005;Rudroff et al 2010), which results in a briefer endurance time for a position task at low to moderate target forces (Baudry et al 2009;Hunter et al 2005Hunter et al , 2008Klass et al 2008;Rudroff et al 2010). Given that the motor performance capabilities of the nondominant arm of left-handed subjects are superior to those of righthanded subjects (Brouwer et al 2001;Caroselli et al 2006;Hoffmann 1997;Hoffmann et al 1997;Judge and Stirling 2003;Przybyla et al 2012), we expected to find that lefthanded subjects would exhibit less of a difference in the endurance time for sustained isometric contractions that have been shown to involve unique control strategies.…”

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Handedness but not dominance influences variability in endurance time for sustained, submaximal contractions

Gordon

Rudroff

Enoka

et al. 2012

Journal of Neurophysiology

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Gordon NM, Rudroff T, Enoka JA, Enoka RM. Handedness but not dominance influences variability in endurance time for sustained, submaximal contractions. J Neurophysiol 108: 1501-1510. First published June 13, 2012 doi:10.1152/jn.01144.2011The purpose of this study was to compare endurance time and accompanying neuromuscular adjustments when left-and right-handed subjects used the dominant and nondominant arms to sustain submaximal contractions that required either force or position control. Ten left-handed and 10 right-handed healthy adults (21 Ϯ 5 yr) participated in the study. Each subject exerted a similar net torque about the elbow joint during the force and position tasks to achieve a target force of 20% maximal voluntary contraction (MVC) force (56 Ϯ 18 N). MVC force declined to a similar level immediately after task failure for left-and righthanded subjects (27 Ϯ 13 vs. 25 Ϯ 15%, P ϭ 0.9). Endurance time for the position task was similar for the dominant and nondominant arms (task ϫ dominance interaction, P ϭ 0.17). Although the difference in endurance time between the two tasks was similar for left-handed (136 Ϯ 165 s) and right-handed individuals (92 Ϯ 73 s, task ϫ handedness interaction, P ϭ 0.38), there was greater variance in the ratio of the endurance times for the force and position tasks for left-handed (0.77) than right-handed subjects (0.13, P Ͻ 0.001; see Fig. 2). Furthermore, endurance time for the force and position tasks was significantly correlated for right-handed subjects (r 2 ϭ 0.62, P Ͻ 0.001), but not for left-handed subjects (r 2 ϭ 0.004, P ϭ 0.79). Multiple regression analyses identified sets of predictor variables for each endurance time, and these differed with handedness and task. Hand dominance, however, did not influence endurance time for either group of subjects. These findings indicate that endurance times for the elbow flexors when performing submaximal isometric contractions that required either force or position control were not influenced by hand dominance but did depend on handedness. electromyography; muscle fatigue; task failure THE PREFERENTIAL USE OF ONE ARM during motor tasks is known as hand dominance and defines the handedness of an individual. A right-handed individual, for example, tends to use the right hand to perform most activities of daily living, such as writing, throwing, using scissors, brushing teeth, cutting with a knife, eating with a spoon, striking a match, and opening a box. However, some actions are more commonly performed with the nondominant limb, which results in each arm developing a unique set of motor skills (Adamo and Martin 2009; Bernard et al.

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Handedness but not dominance influences variability in endurance time for sustained, submaximal contractions

Gordon

Rudroff

Enoka

et al. 2012

Journal of Neurophysiology

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“…During sustained maximal contractions, H-reflex amplitude declines gradually, most likely due to group III and IV afferent input (Duchateau et al 1993). H-reflex paired-pulse suppression, on the other hand, demonstrates a biphasic pattern, with facilitation of the conditioned H early during fatigue and a return of H-reflex suppression as exhaustion approaches (Baudry, Maerz, Gould and Enoka 2011). During intermittent contractions, interposed rest cycles limit metabolite accumulation and H-reflex amplitude increases with fatigue (Loscher et al 1996, Nordlund et al 2004).…”

Section: Discussionmentioning

confidence: 99%

“…One previous report used these two conditioning methods in the upper extremity during a pair of static (isometric) fatigue tasks (Baudry et al 2011). Unlike our dynamic fatigue task, these authors observed pre/post fatigue changes in H-reflex depression.…”

Section: Discussionmentioning

confidence: 99%

“…These observations potentially implicate a similar neural mechanism for heteronymous and homonymous conditioning (e.g., presynaptic inhibition). However, other sources of modulation cannot be ruled out (such as Ib afferent input (Baudry et al 2011)) and we could not methodologically ensure that equal amounts of conditioning stimuli reached the soleus motor neuron pool with the two conditioning methods. Quantification of afferent input in the two methods would require direct recording of potentials at the presynaptic terminal.…”

Section: Discussionmentioning

confidence: 99%

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Dynamic Fatigue Does Not Alter Soleus H-Reflexes Conditioned by Homonymous or Heteronymous Pathways

Oza¹,

Dudley-Javoroski

Shields

2017

Motor Control

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H-reflex depression (diminution of amplitude after a conditioning stimulus) is mediated presynaptically and therefore can help distinguish central versus peripheral mechanisms of fatigue. We examined the effects of a dynamic exercise protocol on H-reflex depression using two conditioning methods: homonymous conditioning (paired-pulse tibial nerve stimulation); and heteronymous conditioning (common peroneal nerve stimulation). Ten subjects performed dynamic contractions of the soleus muscle through 30° ankle range of motion. The concentric phase required a target force of 10% of maximum voluntary isometric contraction (MVIC) and the eccentric phase force target was 80% MVIC. Fatigue persisted for >20 min after cessation of the exercise. Compared with prefatigue values, the dynamic fatigue protocol did not increase presynaptic inhibition after either homonymous or heteronymous conditioning. Peak to peak amplitude of unconditioned H-reflexes was likewise unchanged despite a long term depression of muscle force (long duration fatigue). These results suggest that persistent fatigue after dynamic exercise is attributed to muscle changes and not altered spinal mechanisms.

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“…Input from Ia afferents to the active motor neuron pool can be inhibited due to the depolarization of primary afferent fibers by interneurons and consequently affect the activation of the motor units to the targeted muscle. 47,48 Further, depending on the task that is to be performed, whether position control or force control, older adults demonstrate a decreased ability to regulate presynaptic inhibition compared with young adults. For example, Baudry and Enoka 47 reported that the ability of older adults to regulate presynaptic Ia afferent inhibition was reduced when individuals were tasked to control hand position while supporting a mass (position control) compared with exerting the same force against a rigid constraint (force control).…”

Section: Discussionmentioning

confidence: 99%

The Association Between Knee Extensor Force Steadiness, Force Accuracy, and Mobility in Older Adults Who Have Fallen

Chung-Hoon

Tracy

Dibble

et al. 2016

Journal of Geriatric Physical Therapy

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Background Older adults often experience impaired mobility, lower extremity muscle weakness, and increased fall risk. Furthermore, when older adults perform tasks that require control of submaximal force, impairments in their ability to maintain steady and accurate force output has been reported. Such problems may be related to deteriorating levels of mobility, particularly in older adults who have fallen. Purpose The purpose of this study was to determine whether an association exists between muscle force steadiness (MFS) or muscle force accuracy (MFA) of the knee extensors and mobility in older adults who have fallen. Methods Twenty older adults (x̄ = 77.5 ± 7yrs, 5 males and 15 females) with 2 or more co-morbid conditions and who experienced a fall in the past year underwent assessment of maximal voluntary isometric contraction (MVIC) of the knee extensors. A submaximal target force of 50% of their MVIC was used to determine concentric (CON) and eccentric (ECC) steadiness (the fluctuations in force production) and accuracy (the average distance of the mean force from the target force) measures. Mobility was indicated by the 6 minute walk test (6MWT), the timed up and go (TUG), stair ascent (StA), and stair descent (StD) tests. Correlation analysis was used to assess the relation between measures of muscle force control and mobility. Results The correlations between MFS and mobility were not significant (p>0.05) for either contraction type. However, MFA during ECC contractions only, were correlated significantly with all measures of mobility: 6MWT (r=−0.48, p=0.03), TUG (r=0.68, p=0.01), StA (r=0.60, p=0.01), StD (r=0.75, p<0.01). Conclusion The identification of the relationship between ECC MFA and mobility in older adults who have fallen is novel. While the correlations are not causal, these relationships suggest inaccurate force output during ECC contractions of the knee extensors is linked to impaired mobility.

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Task- and time-dependent modulation of Ia presynaptic inhibition during fatiguing contractions performed by humans

Abstract: Baudry S, Maerz AH, Gould JR, Enoka RM. Task-and timedependent modulation of Ia presynaptic inhibition during fatiguing contractions performed by humans.

Cited by 40 publications

References 37 publications

Handedness but not dominance influences variability in endurance time for sustained, submaximal contractions

Handedness but not dominance influences variability in endurance time for sustained, submaximal contractions

Dynamic Fatigue Does Not Alter Soleus H-Reflexes Conditioned by Homonymous or Heteronymous Pathways

The Association Between Knee Extensor Force Steadiness, Force Accuracy, and Mobility in Older Adults Who Have Fallen

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