scholarly journals Reduction in voluntary activation of elbow and wrist muscles in individuals with chronic hemiparetic stroke

2019 ◽  
Author(s):  
Lindsay R. P. Garmirian ◽  
Julius P. A. Dewald ◽  
Ana Maria Acosta
Keyword(s):  
Upper Extremity ◽  
Voluntary Activation ◽  
Force Output ◽  
Twitch Interpolation ◽  
Paretic Limb ◽  
Full Capacity ◽  
Muscle Groups ◽  
Hemiparetic Stroke ◽  
Chronic Hemiparetic Stroke ◽  
Wrist Flexors

AbstractAfter a stroke, descending drive is impaired due to the loss of corticospinal and corticobulbar projections which causes a reduction in voluntary activation or an inability of the nervous system to activate muscles to their full capacity, which in turn contributes to weakness of the upper extremity. Voluntary activation has not been quantified at specific joints in the upper extremity, in part because directly assessing changes descending drive is difficult. In this study, voluntary activation of elbow and wrist flexors and extensors was assessed in participants with chronic hemiparetic stroke using twitch interpolation. Twitch interpolation uses electrical stimulation to estimate voluntary activation and relies on the principle that there is an inverse relationship between the amplitude of a twitch evoked by a stimulus and the voluntary force output during stimulation (Taylor, 2009). We measured voluntary activation using twitch interpolation as well as maximum voluntary torque (MVT) of the elbow and wrist flexors and extensors in the paretic and non-paretic limb of ten participants post stroke and the dominant and non-dominant limb of 2 control participants. Results show, MVT interlimb differences were significantly greater for stroke participants compared to control, across muscle groups (p≤0.005). For stroke participants, MVT interlimb differences were significantly greater at the wrist compared to the elbow (P=0.003). Voluntary activation was significantly less in the paretic limb compared to the non-paretic, dominant and non-dominant limbs, across participants and muscle groups (p<0.005 for all four muscle groups). For the stroke participants, the voluntary activation interlimb difference was significantly greater for the wrist muscles compared to the elbow muscles (p<0.005). There was a significant positive correlation (r = 0.39, P = .022) between each participant’s impairment level, as measured by a hand specific subscore of the Fugl-Meyer Assessment, and the wrist extensor voluntary activation in the paretic limb but the relationship was not significant for the other muscle groups.

scholarly journals Volume and intramuscular fat content of upper extremity muscles in individuals with chronic hemiparetic stroke

2019 ◽  
Author(s):  
Lindsay R. P. Garmirian ◽  
Ana Maria Acosta ◽  
Ryan Schmid ◽  
Jules P. A. Dewald
Keyword(s):  
Upper Extremity ◽  
Muscle Atrophy ◽  
Upper Limb ◽  
Intramuscular Fat ◽  
Muscle Volume ◽  
Contractile Element ◽  
Paretic Limb ◽  
Hemiparetic Stroke ◽  
Chronic Hemiparetic Stroke ◽  
Wrist Flexors

AbstractStroke survivors often experience upper extremity deficits that make activities of daily living (ADLs) like dressing, cooking and bathing difficult or impossible. Survivors experience paresis, the inability to efficiently and fully activate muscles, which combined with decreased use of the upper extremity, will lead to muscle atrophy and potentially an increase in intramuscular fat. Muscle atrophy has been linked to weakness post stroke and is an important contributor to upper extremity deficits. However, the extent of upper extremity atrophy post hemiparetic stroke is unknown and a better understanding of these changes is needed to inform the direction of intervention-based research. In this study, the volume of contractile tissue and intramuscular fat in the elbow and wrist flexors and extensors were quantified in the paretic and non-paretic upper limb using MRI and the Dixon technique for the first time. Total muscle volume (p≤0.0005) and contractile element volume (p≤0.0005) were significantly smaller in the paretic upper extremity, for all muscle groups studied. The average percent difference between limbs and across participants was 21.3% for muscle volume and 22.9% for contractile element volume. We also found that while the percent intramuscular fat was greater in the paretic limb compared to the non-paretic (p≤0.0005), however, the volume of intramuscular fat was not significantly different between upper limbs (p=0.231). The average volumes of intramuscular fat for the elbow flexors/extensors and wrist flexors/extensors were 28.1, 28.8 and 19.9, 8.8 cm3 in the paretic limb and 29.6, 27.7 and 19.7, 8.8 cm3 in the non-paretic limb. In short, these findings indicate a decrease in muscle volume and not an increase in intramuscular fat, which will contribute to the reduction in strength in the paretic upper limb.

Hemiparetic Gait Parameters in Overground Versus Treadmill Walking

2001 ◽  
Vol 15 (2) ◽  
pp. 105-112 ◽  
Author(s):  
Michelle L. Harris-Love ◽  
Larry W. Forrester ◽  
Richard F. Macko ◽  
Kenneth H. C. Silver ◽  
Gerald V. Smith
Keyword(s):  
Gait Pattern ◽  
Supporting Evidence ◽  
Gait Symmetry ◽  
Paretic Limb ◽  
Hemiparetic Gait ◽  
Gait Parameters ◽  
Stance Time ◽  
Hemiparetic Stroke ◽  
Chronic Hemiparetic Stroke ◽  
Sparse Methods

Objective: Hemiparetic gait is characterized by high stride-cycle variability, di minished stance time, single-limb stance time, and stance/swing ratio in the paretic limb. Recent studies suggest treadmill (TM) training may improve the motor control underlying these variables, but supporting evidence is sparse. Methods: This study compared gait patterns of untrained chronic hemiparetic stroke patients (n = 18; mean, 39.5 months poststroke) during overground (OG) and TM walking at matched velocities. Variables included relative stance time, relative single-limb stance time, stance/swing ratio, peak force, and impulse. Within-subject variability of these meas ures (CV) was used to assess gait pattern stability. Results: OG and TM cycle dura tions were similar, but CVs differed (TM < OG, p < 0.05). In the paretic limb, dif ferences were seen in relative stance time, relative single-limb stance time, and stance/swing ratio, respectively (TM > OG, p < 0.05). These variables decreased in the nonparetic limb during TM walking (p < 0.05 for all). Improved interlimb sym metry and coordination were evidenced by decreased between-limb differences and improved relative temporal phasing, respectively, in the TM condition (p < 0.05). Conclusions: Collectively, these results demonstrate that the TM induces an imme diate alteration toward a more consistent and symmetric gait pattern. Further inves tigation is needed to determine whether TM training leads to motor relearning and neuroplasticity in chronic hemiparetic subjects. Key Words: Stroke—Rehabilitation— Hemiparetic gait-Treadmill-Gait symmetry.

Biomechanical Loading of the American Kettlebell Swing

2015 ◽  
Author(s):  
Jefferey Mitchell ◽  
Wayne M. Johnson ◽  
Bryan Riemann ◽  
Kellen Krajewski ◽  
Cameron W. Coates
Keyword(s):  
Upper Extremity ◽  
Inverse Dynamics ◽  
Future Research ◽  
Mechanical Stimuli ◽  
Force Output ◽  
Orientation Data ◽  
Finite Difference Approximations ◽  
Arm Muscles ◽  
Muscle Groups ◽  
Centers Of Mass

The American kettlebell swing is a variation of the Russian kettlebell swing where the kettlebell is swept in an arc from between the legs to an overhead position with straightened arms. Previous studies involving the kettlebell swing have examined the aerobic and cardiovascular impact of the swing, the variation of mechanical impulse and power generation with kettlebell weight, and compared its efficacy to other types of exercises. However, there have been limited studies examining the dynamic biomechanical loads of the swing on the arm and shoulder. The aim of this study was to establish the mechanical demands of the American kettlebell swing exercise on the arms and shoulders to determine the regions of highest force output and the variation of the forces throughout the swing, all based on percentage of the swing completed. In order to obtain kinematic data, two female subjects with prior kettlebell exercise experience performed one set of fifteen American swings with 8kg and 12kg kettlebells. Position and orientation data was recorded during trials for the kettlebell, joints, and centers of mass of arm segments. Velocity and acceleration data was found using finite-difference approximations. An inverse dynamics method applied to (2-D) planar motion using Newton-Euler equations was used to determine the forces and moments at various joints along the entire arm including the wrist, elbow, and shoulder joints. Data was time normalized as percent of swing, where 0% and 100% indicated the beginning and end of the swing respectively, and approximately 50% denoted the transition between upswing and downswing halves. Results revealed that the arm was under tension during 0% to 35% and 67% to 100% of the swing, indicating the upper torso works to provide the normal force to support the curved motion of the kettlebell. During 36% to 66% of the swing the arm muscles worked in order to support the weight of the kettlebell over the head. While the lower extremity mechanical demands associated with kettlebell swings have been studied, the current results help clarify the upper extremity mechanical demands associated with kettlebell swing exercise. The results of this analysis will better help practitioners to understand the prerequisite upper extremity function needed to perform the full American style swing. The American kettlebell swing carries risks its Russian equivalent does not have, typically breaking form to make the shoulder extension involved with raising the kettlebell above the subjects head. These results suggest that the extra range of motion in the American kettlebell swing prompts different mechanical demands which, in turn, targets different muscle groups from the lower half of the American swing or the Russian kettlebell swing. Finally, because increasing mechanical stimuli is an important component to exercise progression, this analysis fills the void of understanding the effects of changing kettlebell loads on the upper extremity demands. Future research will consider the symmetry of the upper extremity mechanical patterns revealed by this analysis.

Muscle activation in unilateral and bilateral efforts assessed by motor nerve and cortical stimulation

1996 ◽  
Vol 80 (4) ◽  
pp. 1351-1356 ◽  
Author(s):  
R. D. Herbert ◽  
S. C. Gandevia
Keyword(s):  
Muscle Activation ◽  
Motor Nerve ◽  
Voluntary Activation ◽  
Left Elbow ◽  
Twitch Interpolation ◽  
Adductor Muscles ◽  
Muscle Groups ◽  
The Right ◽  
Voluntary Contractions ◽  
Contralateral Muscle

Voluntary muscle activation was measured with twitch interpolation in 11 subjects during attempted maximal voluntary contractions of the right thumb adductor muscles either in isolation (“thumb alone”) or as the subjects simultaneously performed maximal voluntary contractions of the left thumb adductors or left elbow flexors (“both thumbs” or “thumb and elbow”, respectively). During thumb alone contractions, median voluntary activation of the right thumb adductors was 90.3%, and subjects fully activated the thumb adductors on 22% of all contractions. Transcranial magnetic stimulation of the cortex during maximal voluntary efforts produced small twitchlike force increases, suggesting that at least part of the voluntary activation failure was attributable to suboptimal corticospinal drive. Maximal voluntary force produced by the right thumb adductors in the three conditions differed by < 2% (P = 0.21), and the ability to activate the thumb adductors in the both thumbs condition was only marginally less than during thumb alone contractions (median 88.6%; P = 0.004).Thus subjects are usually unable to fully activate their thumb adductors with maximal voluntary efforts, and simultaneous maximal contractions of contralateral muscle groups have little effect on this ability.

scholarly journals Motor Impairment–Related Alterations in Biceps and Triceps Brachii Fascicle Lengths in Chronic Hemiparetic Stroke

2018 ◽  
Vol 32 (9) ◽  
pp. 799-809 ◽  
Author(s):  
Christa M. Nelson ◽  
Wendy M. Murray ◽  
Julius P. A. Dewald
Keyword(s):  
Motor Impairment ◽  
Distal Portion ◽  
Functional Mobility ◽  
Triceps Brachii ◽  
Motor Impairments ◽  
Fascicle Length ◽  
Paretic Limb ◽  
Hemiparetic Stroke ◽  
Long Head ◽  
Chronic Hemiparetic Stroke

Poststroke deficits in upper extremity function occur during activities of daily living due to motor impairments of the paretic arm, including weakness and abnormal synergies, both of which result in altered use of the paretic arm. Over time, chronic disuse and a resultant flexed elbow posture may result in secondary changes in the musculoskeletal system that may limit use of the arm and impact functional mobility. This study utilized extended field-of-view ultrasound to measure fascicle lengths of the biceps (long head) and triceps (distal portion of the lateral head) brachii in order to investigate secondary alterations in muscles of the paretic elbow. Data were collected from both arms in 11 individuals with chronic hemiparetic stroke, with moderate to severe impairment as classified by the Fugl-Meyer assessment score. Across all participants, significantly shorter fascicles were observed in both biceps and triceps brachii ( P < .0005) in the paretic limb under passive conditions. The shortening in paretic fascicle length relative to the nonparetic arm measured under passive conditions remained observable during active muscle contraction for the biceps but not for the triceps brachii. Finally, average fascicle length differences between arms were significantly correlated to impairment level, with more severely impaired participants showing greater shortening of paretic biceps fascicle length relative to changes seen in the triceps across all elbow positions ( r = −0.82, P = .002). Characterization of this secondary adaptation is necessary to facilitate development of interventions designed to reduce or prevent the shortening from occurring in the acute stages of recovery poststroke.

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