Contributions of voluntary activation deficits to hand weakness after stroke

Hoffmann, Gilles; Conrad, Megan O.; Qiu, Dan; Kamper, Derek G.

doi:10.1179/1945511915y.0000000023

Cited by 38 publications

(34 citation statements)

References 44 publications

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“…Though various studies have reported positive outcomes following multiple types of interventions in more mildly impaired individuals ( 5 , 6 ), regaining hand function in individuals with moderate-to-severe impairments still remains a challenge. This is largely due to impairments, such as the loss of volitional finger extension ( 7 , 8 ), muscle coactivation ( 7 ), involuntary coupling of wrist and finger flexion with certain shoulder and elbow movements ( 9 ), and somatosensory deficits ( 10 ).…”

Section: Introductionmentioning

confidence: 99%

Improving Hand Function of Severely Impaired Chronic Hemiparetic Stroke Individuals Using Task-Specific Training With the ReIn-Hand System: A Case Series

et al. 2018

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Purpose: In this study, we explored whether improved hand function is possible in poststroke chronic hemiparetic individuals with severe upper limb motor impairments when they participate in device-aided task-specific practice.Subjects: Eight participants suffering from chronic stroke (>1-year poststroke, mean: 11.2 years) with severely impaired upper extremity movement (Upper Extremity Subscale of the Fugl-Meyer Motor Assessment (UEFMA) score between 10 and 24) participated in this study.Methods: Subjects were recruited to participate in a 20-session intervention (3 sessions/7 weeks). During each session, participants performed 20–30 trials of reaching, grasping, retrieving, and releasing a jar with the assistance of a novel electromyography-driven functional electrical stimulation (EMG-FES) system.This EMG-FES system allows for Reliable and Intuitive use of the Hand (called ReIn-Hand device) during multi-joint arm movements. Pre-, post-, and 3-month follow-up outcome assessments included the UEFMA, Cherokee McMaster Stroke Assessment, grip dynamometry, Box and Blocks Test (BBT), goniometric assessment of active and passive ranges of motion (ROMs) of the wrist and the metacarpophalangeal flexion and extension (II, V fingers), Nottingham Sensory Assessment–Stereognosis portion (NSA), and Cutaneous Sensory Touch Threshold Assessment.Results: A nonparametric Friedman test of differences found significant changes in the BBT scores (χ2 = 10.38, p < 0.05), the passive and active ROMs (χ2 = 11.31, p < 0.05 and χ2 = 12.45, p < 0.01, respectively), and the NSA scores (χ2 = 6.42, p < 0.05) following a multi-session intervention using the ReIn-Hand device.Conclusions: These results suggest that using the ReIn-Hand device during reaching and grasping activities may contribute to improvements in gross motor function and sensation (stereognosis) in individuals with chronic severe UE motor impairment following stroke.

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Section: Introductionmentioning

confidence: 99%

Improving Hand Function of Severely Impaired Chronic Hemiparetic Stroke Individuals Using Task-Specific Training With the ReIn-Hand System: A Case Series

et al. 2018

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“…This muscle weakness post-stroke has been attributed to alterations in the descending voluntary command, and to anatomical and physiological changes within the muscle ( McComas et al, 1971 ; Bourbonnais and Noven, 1989 ; Dattola et al, 1993 ). Previous studies have identified impairments in voluntary muscle activation ( Riley and Bilodeau, 2002 ; Knorr et al, 2011 ; Bowden et al, 2014 ; Hoffmann et al, 2016 ), altered motor unit (MU) firing rates ( Rosenfalck and Andreassen, 1980 ; McNulty et al, 2014 ), a reduced ability to modulate MU firing ( Gemperline et al, 1995 ; Mottram et al, 2014 ; Li et al, 2015 ) and abnormal MU recruitment patterns ( Tang and Rymer, 1981 ; Hu et al, 2015 , 2016 ), all of which may contribute to muscle weakness post-stroke.…”

Section: Introductionmentioning

confidence: 99%

Motor Unit Activity during Fatiguing Isometric Muscle Contraction in Hemispheric Stroke Survivors

McManus

Rymer

et al. 2017

Front. Hum. Neurosci.

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Enhanced muscle weakness is commonly experienced following stroke and may be accompanied by increased susceptibility to fatigue. To examine the contributions of central and peripheral factors to isometric muscle fatigue in stroke survivors, this study investigates changes in motor unit (MU) mean firing rate, and action potential duration during, and directly following, a sustained submaximal fatiguing contraction at 30% maximum voluntary contraction (MVC). A series of short contractions of the first dorsal interosseous muscle were performed pre- and post-fatigue at 20% MVC, and again following a 10-min recovery period, by 12 chronic stroke survivors. Individual MU firing times were extracted using surface EMG decomposition and used to obtain the spike-triggered average MU action potential waveforms. During the sustained fatiguing contraction, the mean rate of change in firing rate across all detected MUs was greater on the affected side (-0.02 ± 0.03 Hz/s) than on the less-affected side (-0.004 ± 0.003 Hz/s, p = 0.045). The change in firing rate immediately post-fatigue was also greater on the affected side than less-affected side (-13.5 ± 20 and 0.1 ± 19%, p = 0.04). Mean MU firing rates increased following the recovery period on the less-affected side when compared to the affected side (19.3 ± 17 and 0.5 ± 20%, respectively, p = 0.03). MU action potential duration increased post-fatigue on both sides (10.3 ± 1.2 to 11.2 ± 1.3 ms on the affected side and 9.9 ± 1.7 to 11.2 ± 1.9 ms on the less-affected side, p = 0.001 and p = 0.02, respectively), and changes in action potential duration tended to be smaller in subjects with greater impairment (p = 0.04). This study presents evidence of both central and peripheral fatigue at the MU level during isometric fatiguing contraction for the first time in stroke survivors. Together, these preliminary observations indicate that the response to an isometric fatiguing contraction differs between the affected and less-affected side post-stroke, and may suggest that central mechanisms observed here as changes in firing rate are the dominant processes leading to task failure on the affected side.

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“…In healthy individuals, differences in strength between people and groups is highly correlated with muscle mass [ 28 ] with minimal differences between men and women in their ability to activate the available muscle [ 24 , 29 ]. Following stroke, impaired neural activation of the muscle by the cortex [ 15 , 30 , 31 ] plays a larger role in decrements in strength than for healthy controls. Coupled with muscle atrophy, both neural and muscular mechanisms contribute to sarcopenia [ 32 ] and the associated weakness.…”

Section: Discussionmentioning

confidence: 99%

“…Individuals who could contract and relax their muscles faster also could walk faster. Damage to the motor cortex following stroke not only interferes with the ability to fully activate the muscle [ 31 , 30 ], but also likely impairs the speed with which muscles are fully activated due to stroke-related changes in rate modulation and recruitment. In addition, there was positive correlation between baseline resting twitch amplitudes and walking speed.…”

Section: Discussionmentioning

confidence: 99%

Sex Differences in Neuromuscular Fatigability of the Knee Extensors Post-Stroke

et al. 2017

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Background and Purpose: Despite the implications of optimizing strength training post-stroke, little is known about the differences in fatigability between men and women with chronic stroke. The purpose of this study was to determine the sex differences in knee extensor muscle fatigability and potential mechanisms in individuals with stroke. Methods: Eighteen participants (10 men, eight women) with chronic stroke (≥6 months) and 23 (12 men, 11 women) nonstroke controls participated in the study. Participants performed an intermittent isometric contraction task (6 s contraction, 3 s rest) at 30% of maximal voluntary contraction (MVC) torque until failure to maintain the target torque. Electromyography was used to determine muscle activation and contractile properties were assessed with electrical stimulation of the quadriceps muscles. Results: Individuals with stroke had a briefer task duration (greater fatigability) than nonstroke individuals (24.1 ± 17 min vs. 34.9 ± 16 min). Men were more fatigable than women for both nonstroke controls and individuals with stroke (17.9 ± 9 min vs. 41.6 ± 15 min). Individuals with stroke had less fatigue-related changes in muscle contractile properties and women with stroke differed in their muscle activation strategy during the fatiguing contractions. Conclusions: Men and women fatigue differently post-stroke and this may be due to the way they neurally activate muscle groups.

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Contributions of voluntary activation deficits to hand weakness after stroke

Abstract: Although extrinsic finger muscles could be successfully recruited electrically, voluntary excitation of these muscles was substantially limited in stroke survivors. Thus, finger weakness after stroke results predominantly from the inability to fully activate the muscle voluntarily.

Cited by 38 publications

References 44 publications

Improving Hand Function of Severely Impaired Chronic Hemiparetic Stroke Individuals Using Task-Specific Training With the ReIn-Hand System: A Case Series

Improving Hand Function of Severely Impaired Chronic Hemiparetic Stroke Individuals Using Task-Specific Training With the ReIn-Hand System: A Case Series

Motor Unit Activity during Fatiguing Isometric Muscle Contraction in Hemispheric Stroke Survivors

Sex Differences in Neuromuscular Fatigability of the Knee Extensors Post-Stroke

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