Preservation of Directly Stimulated Muscle Strength in Hemiplegia Due to Stroke

Landau, William M.; Sahrmann, Shirley A.

doi:10.1001/archneur.59.9.1453

Cited by 48 publications

(29 citation statements)

References 39 publications

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“…In addition, potentiation may also occur when multiple synergistic muscles are activated during functional movements (De Luca and Erim 2002;Huang and Abraham 2001). Additionally, Landau and Sahrmann (2002) demonstrated that the paretic tibialis anterior muscle of individuals with stroke had lower levels of maximal voluntary torque, but not electrically stimulated force, compared with control subjects, suggesting that the central regulation of muscle activation may be disrupted. Such observations agree with Tang and Rymer (1981) who found that the amount of EMG produced per unit force was greater in the paretic elbow flexor muscles compared with controls and they attributed this increased recruitment from a compensation to the reduced mean motor unit discharge rate that they observed in the paretic muscles.…”

Section: Limitations and Conclusionmentioning

confidence: 99%

Saturated Muscle Activation Contributes to Compensatory Reaching Strategies After Stroke

McCrea¹,

Eng²,

Hodgson³

2005

Journal of Neurophysiology

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. The control and execution of movement could potentially be altered by the presence of stroke-induced weakness if muscles are incapable of generating sufficient power. The purpose of this study was to identify compensatory strategies during a forward (sagittal) reaching task for 20 persons with chronic stroke and 10 healthy age-matched controls. We hypothesized that the paretic anterior deltoid would be maximally activated (i.e., saturated) during a reaching task and that task completion would require activation of additional muscles, resulting in compensatory movements out of the sagittal plane. For reaching movements by control subjects, joint motion remained largely in the sagittal plane and hand trajectories were smooth and direct. Movement characteristics of the nonparetic arm of stroke subjects were similar to control subjects except for small increases in the abduction angle and the percentage that anterior deltoid was activated. In contrast, reaching movements of the paretic arm of stroke subjects were characterized by increased activation of all muscles, especially the lateral deltoid, in addition to the anterior deltoid, with resulting shoulder abduction power and segmented and indirect hand motion. For the paretic arm of stroke subjects, muscle and kinetic compensations increased with impairment severity and weaker muscles were used at a higher percentage of their available muscle activity. These results suggest that the inability to generate sufficient force with the typical agonists involved during a forward reaching task may necessitate compensatory muscle recruitment strategies to complete the task.

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Section: Limitations and Conclusionmentioning

confidence: 99%

Saturated Muscle Activation Contributes to Compensatory Reaching Strategies After Stroke

McCrea¹,

Eng²,

Hodgson³

2005

Journal of Neurophysiology

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“…3 This loss of force production occurs because of an interruption of the pyramidal tract. 4 In the early phase of recovery, many patients are unable to maintain an upright position in sitting or standing, and have no ability to move the affected arm.…”

Section: Central Weakness: Loss Of Force Productionmentioning

confidence: 99%

“…[20][21][22] Today, the nature of spasticity, its underlying mechanisms, and its relevance to rehabilitation practice are being widely investigated and debated. 3,23,24 At the same time, the increasing popularity of medical interventions for spasticity (for example, botulotoxin injections) suggests its treatment remains a priority within the medical community.…”

Section: Spasticity and Hypertonicitymentioning

confidence: 99%

The Shoulder in Hemiplegia

Ryerson¹,

Levit²

2004

Physical Therapy of the Shoulder

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“…Ada et al 2 discovered that stroke subjects were relatively stronger when both flexors and extensors were in their lengthened range and relatively weaker when the muscles were in their shortened ranges. However, the contractile capacity of the paretic muscle itself is not altered after stroke 5 ; rather, there may be a deficient central recruitment of motor units. Some investigators have suggested that after stroke, impairment of voluntary strength is associated with deficient motor unit recruitment and firing frequencies insufficient to generate a fused tetanus of the involved motor units.…”

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confidence: 99%

Central Compensation at Short Muscle Range Is Differentially Affected in Cortical Versus Subcortical Strokes

Renner

Woldag

Hummelsheim

2006

Stroke

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Background and Purpose-The active force generated by a single muscle fiber is greatest in midrange. In healthy subjects, the reduced muscle force at short muscle length is partially compensated by modified patterns of muscle activation, probably central in origin. These patterns are presumed to be deficient after stroke. We examined the excitability muscle-length relation in stroke patients and healthy controls and hypothesized about its alteration in stroke patients. Methods-Corticospinal excitability was assessed in 31 stroke patients (19 subcortical, 12 cortical) and 19 healthy volunteers by transcranial magnetic stimulation. We recorded the motor evoked potentials (MEPs) simultaneously from the biceps brachii and the triceps brachii muscles at 0°, 20°, 40°, 60°, 80°, 100°, and 120°degrees of elbow flexion (0°b eing full elbow extension). Results-Normal subjects revealed a significant increase in MEP amplitudes at shortened muscle lengths for both the flexor and extensor muscles (PϽ0.001). Multivariate variance analysis revealed that the MEP-angle curves of cortical stroke patients were significantly different from those of the control group for both muscles, lacking an increase of corticospinal excitability at short muscle length. Yet the MEP-angle curves for the subcortical stroke patients did not show a statistically significant difference from the control group for either muscle. Conclusion-Cortical and subcortical strokes differentially affect the corticospinal excitability muscle-length relation. This may account for the reported disproportionate decrease in muscle strength at shortened range after stroke.

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Preservation of Directly Stimulated Muscle Strength in Hemiplegia Due to Stroke

Cited by 48 publications

References 39 publications

Saturated Muscle Activation Contributes to Compensatory Reaching Strategies After Stroke

Saturated Muscle Activation Contributes to Compensatory Reaching Strategies After Stroke

The Shoulder in Hemiplegia

Central Compensation at Short Muscle Range Is Differentially Affected in Cortical Versus Subcortical Strokes

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