Abnormal force--EMG relations in paretic limbs of hemiparetic human subjects.

Tang, Aco; Rymer, William Z.

doi:10.1136/jnnp.44.8.690

Cited by 197 publications

(110 citation statements)

References 9 publications

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“…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. However, others have reported that the EMG-force relationship in the elbow is similar between stroke patients and controls (Fellows et al 1994).…”

Section: Limitations and Conclusionsupporting

confidence: 81%

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 Conclusionsupporting

confidence: 81%

Saturated Muscle Activation Contributes to Compensatory Reaching Strategies After Stroke

McCrea¹,

Eng²,

Hodgson³

2005

Journal of Neurophysiology

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“…There is also evidence (Tang & Rymer, 1981;Dietz et al, 1986). Weakness from these sources is compounded by changes in the properties of motor units and in morphological and mechanical changes in the muscles which occur adaptively as a consequence of denervation, but also of decreased physical activity and disuse (e.g., Farmer et al, 1993;McComas, 1993 (Carr & Shepherd, 1998;2000).…”

Section: Introductionmentioning

confidence: 94%

Exercise and Training to Optimize Functional MotorPerformance in Stroke: Driving Neural Reorganization?

Shepherd

2001

Neural Plasticity

140

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“…Muscle weakness, or the inability to generate normal levels of force, is a common consequence of stroke and has clinically been recognized as one of the limiting factors in physical function in the motor rehabilitation of stroke persons with hemiparesis 19 . Possible factors contributing to muscle weakness in the lower limbs following stroke include decreased number of functioning motor units, disrupted recruitment order of motor units 21 , and decreased motor unit firing rates 22 in addition to muscle atrophy following disuse 23 . Considering that we used the ratio to compare lower limbs, we can assume that this decreased force production in the paretic LL still cannot be explained simply by muscle weakness following stroke.…”

Section: Discussionmentioning

confidence: 99%

Strength deficit of knee flexors is dependent on hip position in adults with chronic hemiparesis

Michaelsen¹,

Ovando²,

Bortolotti³

et al. 2013

Braz. J. Phys. Ther.

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| Background: The extent to which muscle length affects force production in paretic lower limb muscles after stroke in comparison to controls has not been established. Objectives: To investigate knee flexor strength deficits dependent on hip joint position in adults with hemiparesis and compare with healthy controls. Method: a cross-sectional study with ten subjects with chronic (63±40 months) hemiparesis with mild to moderate lower limb paresis (Fugl-Meyer score 26±3) and 10 neurologically healthy controls. Isometric knee flexion strength with the hip positioned at 90° and 0° of flexion was assessed randomly on the paretic and non-paretic side of hemiparetic subjects and healthy controls. Subjects were asked to perform a maximal isometric contraction sustained for four seconds and measured by a dynamometer. The ratio of knee flexor strength between these two hip positions was calculated: Hip 0°/Hip 90°. Also, locomotor capacity was evaluated by the timed up and go test and by walking velocity over 10 meters. Results: In subjects with hemiparesis, absolute knee flexion torque decreased (p<0.001) with the hip in extension (at 0°). The ratio of knee flexor torque Hip 0°/Hip 90° on the paretic side in hemiparetics was lower than in controls (p=0.02). Conclusions: Weakness dependent on joint position is more significant in the paretic lower limb of adults with hemiparesis when compared to controls. More attention should be given to lower limb muscle strengthening exercises in individuals with stroke, with emphasis on the strengthening exercises in positions in which the muscle is shortened.Keywords: stroke; lower extremity; muscle weakness; physical therapy; rehabilitation. HOW TO CITE THIS ARTICLEMichaelsen SM, Ovando AC, Bortolotti A, Bandini B. Strength deficit of knee flexors is dependent on hip position in adults with chronic hemiparesis. Braz J Phys Ther. 2013 Jan-Feb; 17(1):86-91. http://dx

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Abnormal force--EMG relations in paretic limbs of hemiparetic human subjects.

Cited by 197 publications

References 9 publications

Saturated Muscle Activation Contributes to Compensatory Reaching Strategies After Stroke

Saturated Muscle Activation Contributes to Compensatory Reaching Strategies After Stroke

Exercise and Training to Optimize Functional MotorPerformance in Stroke: Driving Neural Reorganization?

Strength deficit of knee flexors is dependent on hip position in adults with chronic hemiparesis

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