Fatigue and Motor Redundancy: Adaptive Increase in Finger Force Variance in Multi-Finger Tasks

Singh, Tarkeshwar; Skm, Varadhan; Zatsiorsky, Vladimir M.; Latash, Mark L.

doi:10.1152/jn.00077.2010

Cited by 65 publications

(84 citation statements)

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“…Some studies have shown that in motor tasks that involve a redundant set of elements, the goal-relevant features of performance are relatively preserved during fatigue (Gates & Dingwell, 2008; Huffenus, Amarantini, & Forestier, 2006). We have also shown this to be true in accurate force production tasks (Park, Singh, Zatsiorsky, & Latash, 2012; Singh et al, 2010b; Singh, Zatsiorsky, & Latash, 2012). In the current study, we investigated the effects of exercise-induced fatigue of a single digit on motor variability and digit coordination in a static prehension task.…”

Section: Introductionsupporting

confidence: 54%

“…Previous studies on exercise induced muscle fatigue have shown an increase in motor variability (Enoka & Stuart, 1992; Singh, SKM, Zatsiorsky, & Latash, 2010b) and altered motor coordination (Côté, Mathieu, Levin, & Feldman, 2002; Forestier & Nougier, 1998; Missenard, Mottet, & Perrey, 2008). Some studies have shown that in motor tasks that involve a redundant set of elements, the goal-relevant features of performance are relatively preserved during fatigue (Gates & Dingwell, 2008; Huffenus, Amarantini, & Forestier, 2006).…”

Section: Introductionmentioning

confidence: 98%

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Prehension Synergies During Fatigue of a Single Digit: Adaptations in Control With Referent Configurations

Singh¹,

Zatsiorsky²,

Latash³

2014

Motor Control

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The purpose of the current study was to investigate the effects of exercise-induced fatigue of a digit on prehension synergies in a static precision grasp. One group of participants performed the fatiguing exercise using the thumb (group-thumb) and the second group performed the exercise using the index finger (group-index). Our first hypothesis was that fatigue would trigger changes in the co-variation of forces and moments of force that violate the principle of superposition. This hypothesis was not confirmed. The second hypothesis was that indices of force stabilizing synergies during fatigue would increase at both levels of the hierarchy. This hypothesis was partially confirmed only for group-index. The last hypothesis was that fatigue of TH would have stronger effects at the TH-VF level while fatigue of the index finger would have stronger effects at the IF level. This hypothesis was also partially confirmed.

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Section: Introductionsupporting

confidence: 54%

Section: Introductionmentioning

confidence: 98%

Prehension Synergies During Fatigue of a Single Digit: Adaptations in Control With Referent Configurations

Singh¹,

Zatsiorsky²,

Latash³

2014

Motor Control

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“…The basal ganglia have been implicated in action initiation (Sanes 1985;Stelmach et al 1986); in particular, episodes of freezing typical of PD have been interpreted as reflecting the impaired action preparation processes (Vercruysse et al 2011). Our observations of the significantly reduced and delayed ASAs suggest a specific problem with action initiation in PD.…”

Section: Possible Neurophysiological Mechanisms Of Impaired Synergiesmentioning

confidence: 99%

Changes in multifinger interaction and coordination in Parkinson's disease

Park

Lewis

et al. 2012

Journal of Neurophysiology

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135

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In this study, we tested several hypotheses related to changes in finger interaction and multifinger synergies during multifinger force production tasks in Parkinson's disease. Ten patients with Parkinson's disease, mostly early stage, and 11 healthy control subjects participated in the study. Synergies were defined as covaried adjustment of commands to fingers that stabilized the total force produced by the hand. Both Parkinson's disease patients and control subjects performed accurate isometric force production tasks with the fingers of both the dominant and nondominant hands. The Parkinson's disease patients showed significantly lower maximal finger forces and higher unintended force production (enslaving). These observations suggest that changes in supraspinal control have a major effect on finger individuation. The synergy indexes in the patients were weaker in both steady-state and cyclic force production tasks compared with the controls. These indexes also were stronger in the left (nondominant) hand in support of the dynamic-dominance hypothesis. Half of the patients could not perform the cyclic task at the highest frequency (2 Hz). Anticipatory adjustments of synergies prior to a quick force pulse production were delayed and reduced in the patients compared with the controls. Similar differences were observed between the asymptomatic hands of the patients with symptoms limited to one side of the body and matched hands of control subjects. Our study demonstrates that the elusive changes in motor coordination in Parkinson's disease can be quantified objectively, even in patients at a relatively early stage of the disease. The results suggest an important role of the basal ganglia in synergy formation and demonstrate a previously unknown component of impaired feedforward control in Parkinson's disease reflected in the reduced and delayed anticipatory synergy adjustments.

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“…Changes in enslaving have been documented over years of specialized practice (Slobounov et al 2002), with healthy aging (Shinohara et al 2003, and with neurological disorder (Park et al 2012). Several recent studies have provided evidence for changes in enslaving occurring relatively quickly, over a single 1-h session involving finger fatigue or specialized practice (Singh et al 2010;Wu et al 2013). The results presented here suggest that enslaving may be an even more volatile phenomenon than the previously cited articles suggest: we observed changes in enslaving within a single trial, over the time course of seconds (Fig.…”

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confidence: 99%

Stability of multifinger action in different state spaces

Reschechtko

Zatsiorsky

Latash

2014

Journal of Neurophysiology

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Reschechtko S, Zatsiorsky VM, Latash ML. Stability of multifinger action in different state spaces. J Neurophysiol 112: 3209-3218, 2014. First published September 24, 2014 doi:10.1152/jn.00395.2014.-We investigated stability of action by a multifinger system with three methods: analysis of intertrial variance, application of transient perturbations, and analysis of the system's motion in different state spaces. The "inverse piano" device was used to apply transient (lifting-andlowering) perturbations to individual fingers during single-and twofinger accurate force production tasks. In each trial, the perturbation was applied either to a finger explicitly involved in the task or one that was not. We hypothesized that, in one-finger tasks, task-specific stability would be observed in the redundant space of finger forces but not in the nonredundant space of finger modes (commands to explicitly involved fingers). In two-finger tasks, we expected that perturbations applied to a nontask finger would not contribute to task-specific stability in mode space. In contrast to our expectations, analyses in both force and mode spaces showed lower stability in directions that did not change total force output compared with directions that did cause changes in total force. In addition, the transient perturbations led to a significant increase in the enslaving index. We consider these results within a theoretical scheme of control with referent body configurations organized hierarchically, using multiple few-to-many mappings organized in a synergic way. The observed volatility of enslaving, greater equifinality of total force compared with elemental variables, and large magnitude of motor equivalent motion in both force and mode spaces provide support for the concept of task-specific stability of performance and the existence of multiple neural loops, which ensure this stability. redundancy; abundance; synergy; referent configuration; uncontrolled manifold hypothesis; equifinality; enslaving ONE OF THE FUNDAMENTAL PROBLEMS of motor control is that of redundancy (Bernstein 1967): at any level of description of the system involved in movement production, the number of elements (and of their output variables, elemental variables) is higher than the number of constraints associated with typical motor tasks. Recently, the problem of motor redundancy has been revisited in the context of the principle of motor abundance (Gelfand and Latash 1998;Latash 2012). This approach posits a way for the central nervous system (CNS) to take advantage of all of the elemental variables at its disposal to ensure stability of movement, rather than requiring the CNS to achieve a single, optimal solution by eliminating redundant degrees of freedom. Thus the principle of abundance avoids requiring computational, and physiologically unfeasible, control schemes, which involve explicit instruction to all body structures involved in a given action.A theoretical scheme has been developed, which unites the principle of abundance with the idea of hierarchical...

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Fatigue and Motor Redundancy: Adaptive Increase in Finger Force Variance in Multi-Finger Tasks

Cited by 65 publications

References 74 publications

Prehension Synergies During Fatigue of a Single Digit: Adaptations in Control With Referent Configurations

Prehension Synergies During Fatigue of a Single Digit: Adaptations in Control With Referent Configurations

Changes in multifinger interaction and coordination in Parkinson's disease

Stability of multifinger action in different state spaces

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