Sense of Effort Determines Lower Limb Force Production During Dynamic Movement in Individuals With Poststroke Hemiparesis

2009 ◽  
Vol 23 (8) ◽  
pp. 811-818 ◽  
Author(s):  
Ann M. Simon ◽  
Brian M. Kelly ◽  
Daniel P. Ferris
Keyword(s):  
Lower Limb ◽  
Maximum Voluntary Contraction ◽  
Force Production ◽  
Voluntary Contraction ◽  
Sense Of Effort ◽  
Paretic Limb ◽  
Significant Difference ◽  
Force Scaling ◽  
Limb Rehabilitation ◽  
Isometric Forces

Objective. This study’s purpose was to determine if individuals who have had a stroke primarily use sense of effort to gauge force production during static and dynamic lower limb contractions. If relying on sense of effort while attempting to generate equal limb forces, participants should produce equal percentages of their maximum voluntary strength rather than equal absolute forces in their limbs. Methods. Ten stroke participants performed isometric and isotonic lower limb extensions on an exercise machine. Results. When participants attempted to produce equal bilateral isometric forces, there was a significant difference in absolute force between limbs (ANOVA, P < .0001) but no significant difference when force was normalized to each limb’s maximum voluntary contraction (MVC) force ( P = .5129). During bilateral isotonic contractions, participants produced less absolute force in their paretic limb ( P = .0005) and less relative force in their paretic limb (normalized to MVC force) when participants were given no instructions on how to perform the extension ( P = .0002). When participants were instructed to produce equal forces, there was no significant difference between relative forces in the 2 limbs ( P = .2111). Conclusions. For both isometric and isotonic conditions hemiparetic participants relied primarily on sense of effort, rather than proprioceptive feedback, for gauging lower limb force production. This outcome indicates that sense of effort is the major factor determining force production during movements. Lower limb rehabilitation therapies should not only train strength in the paretic limb but should also train patients to recalibrate force-scaling abilities to improve function.

scholarly journals The Effects of Spinal Manipulation on Motor Unit Behavior

2021 ◽  
Vol 11 (1) ◽  
pp. 105
Author(s):  
Lucien Robinault ◽  
Aleš Holobar ◽  
Sylvain Crémoux ◽  
Usman Rashid ◽  
Imran Khan Niazi ◽  
...  
Keyword(s):  
Motor Unit ◽  
Conduction Velocity ◽  
Spinal Manipulation ◽  
Maximum Voluntary Contraction ◽  
Force Production ◽  
Movement Control ◽  
Position Sense ◽  
Joint Position Sense ◽  
Voluntary Contraction ◽  
Passive Movement

Over recent years, a growing body of research has highlighted the neural plastic effects of spinal manipulation on the central nervous system. Recently, it has been shown that spinal manipulation improved outcomes, such as maximum voluntary force and limb joint position sense, reflecting improved sensorimotor integration and processing. This study aimed to further evaluate how spinal manipulation can alter neuromuscular activity. High density electromyography (HD sEMG) signals from the tibialis anterior were recorded and decomposed in order to study motor unit changes in 14 subjects following spinal manipulation or a passive movement control session in a crossover study design. Participants were asked to produce ankle dorsiflexion at two force levels, 5% and 10% of maximum voluntary contraction (MVC), following two different patterns of force production (“ramp” and “ramp and maintain”). A significant decrease in the conduction velocity (p = 0.01) was observed during the “ramp and maintain” condition at 5% MVC after spinal manipulation. A decrease in conduction velocity suggests that spinal manipulation alters motor unit recruitment patterns with an increased recruitment of lower threshold, lower twitch torque motor units.

A STUDY OF MODELS FOR HANDGRIP FORCE PREDICTION FROM SURFACE ELECTROMYOGRAPHY OF EXTENSOR MUSCLE

2009 ◽  
Vol 21 (02) ◽  
pp. 81-88 ◽  
Author(s):  
Wensheng Hou ◽  
Xiaolin Zheng ◽  
Yingtao Jiang ◽  
Jun Zheng ◽  
Chenglin Peng ◽  
...  
Keyword(s):  
Root Mean Square ◽  
Surface Electromyography ◽  
Random Sequence ◽  
Maximum Voluntary Contraction ◽  
Force Production ◽  
Voluntary Contraction ◽  
Mean Square ◽  
Force Level ◽  
Force Output ◽  
Mean Square Errors

Force production involves the coordination of multiple muscles, and the produced force levels can be attributed to the electrophysiology activities of those related muscles. This study is designed to explore the activity modes of extensor carpi radialis longus (ECRL) using surface electromyography (sEMG) at the presence of different handgrip force levels. We attempt to compare the performance of both the linear and nonlinear models for estimating handgrip forces. To achieve this goal, a pseudo-random sequence of handgrip tasks with well controlled force ranges is defined for calibration. Eight subjects (all university students, five males, and three females) have been recruited to conduct both calibration and voluntary trials. In each trial, sEMG signals have been acquired and preprocessed with Root–Mean–Square (RMS) method. The preprocessed signals are then normalized with amplitude value of Maximum Voluntary Contraction (MVC)-related sEMG. With the sEMG data from calibration trials, three models, Linear, Power, and Logarithmic, are developed to correlate the handgrip force output with the sEMG activities of ECRL. These three models are subsequently employed to estimate the handgrip force production of voluntary trials. For different models, the Root–Mean–Square–Errors (RMSEs) of the estimated force output for all the voluntary trials are statistically compared in different force ranges. The results show that the three models have different performance in different force ranges. Linear model is suitable for moderate force level (30%–50% MVC), whereas a nonlinear model is more accurate in the weak force level (Power model, 10%–30% MVC) or the strong force level (Logarithmic model, 50%–80% MVC).

Maintenance of Uncued Isometric Contractions by Blind and Sighted

1979 ◽  
Vol 49 (2) ◽  
pp. 475-479
Author(s):  
Claudia G. Emes
Keyword(s):  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Isometric Contractions ◽  
Hand Grip ◽  
Significant Difference ◽  
Static Contractions

A comparison of 10 blind and 10 sighted subjects to a proprioceptive task was examined by analysis of response to maintenance of uncued static contractions. In attempting to sustain hand-grip tensions at specified percentages of maximum voluntary contraction, blind and sighted groups showed no significant difference in performance.

The strength of the corticospinal coherence depends on the predictability of modulated isometric forces

2013 ◽  
Vol 109 (6) ◽  
pp. 1579-1588 ◽  
Author(s):  
Ignacio Mendez-Balbuena ◽  
Jose Raul Naranjo ◽  
Xi Wang ◽  
Agnieska Andrykiewicz ◽  
Frank Huethe ◽  
...  
Keyword(s):  
Sensory Feedback ◽  
Muscle Activation ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Visuomotor Task ◽  
Gamma Range ◽  
Cortical Motor ◽  
Contralateral Hand ◽  
Hand Motor Area ◽  
Isometric Forces

Isometric compensation of predictably frequency-modulated low forces is associated with corticomuscular coherence (CMC) in beta and low gamma range. It remains unclear how the CMC is influenced by unpredictably modulated forces, which create a mismatch between expected and actual sensory feedback. We recorded electroencephalography from the contralateral hand motor area, electromyography (EMG), and the motor performance of 16 subjects during a visuomotor task in which they had to isometrically compensate target forces at 8% of the maximum voluntary contraction with their right index finger. The modulated forces were presented with predictable or unpredictable frequencies. We calculated the CMC, the cortical motor alpha-, beta-, and gamma-range spectral powers (SP), and the task-related desynchronization (TRD), as well as the EMG SP and the performance. We found that in the unpredictable condition the CMC was significantly lower and associated with lower cortical motor SP, stronger TRD, higher EMG SP, and worse performance. The findings suggest that due to the mismatch between predicted and actual sensory feedback leading to higher computational load and less stationary motor state, the unpredictable modulation of the force leads to a decrease in corticospinal synchrony, an increase in cortical and muscle activation, and a worse performance.

scholarly journals Crossfit Practice: An Electromyographic Analysis of Masticatory Muscles

2020 ◽  
Author(s):  
Nayara Soares da Silva ◽  
Marcelo Palinkas ◽  
Evandro Marianetti Fioco ◽  
Edson Donizetti Verri ◽  
Saulo César Vallin Fabrin ◽  
...  
Keyword(s):  
Maximum Voluntary Contraction ◽  
Masticatory Muscles ◽  
Voluntary Contraction ◽  
Control Group ◽  
Electromyographic Activity ◽  
Physical Conditioning ◽  
Striated Muscles ◽  
Functional Changes ◽  
Significant Difference ◽  
The Impact

Abstract Background: CrossFit is a regular high-intensity physical conditioning exercise for skeletal striated muscles, which promotes functional changes in the human body. The aim of this study was to investigate the impact of CrossFit exercise on the electromyographic activity of the masseter and temporalis muscles. Methods: Forty participants were divided into two groups: athletes who practiced CrossFit (n=20) and controls who did not practice sports (n=20). The electromyographic activities of the masseter and temporalis muscles were measured using mandibular tasks at rest, protrusion, right laterality, left laterality, and dental clenching in maximum voluntary contraction and habitual chewing of peanuts and raisins. Both the groups were matched for age, sex, and body mass index. The data were analyzed using the t-test with a 5% significance level. Results: Reduced electromyographic activities were found in all mandibular tasks in the CrossFit group than in the control group, with a significant difference for the right masseter (p=0.01), left masseter (p=0.001), and left temporal muscles (p=0.001) at mandibular rest; right (p=0.001) and left (p=0.001) masseter in chewing of peanuts. Conclusion: The results of this study suggest that CrossFit promotes positive changes in electromyographic activity of the masticatory muscles, especially in the mandibular rest and chewing of hard food. CrossFit exercise practiced within the appropriate technical protocols improves masticatory muscle function.

scholarly journals Acute Effect of High-Intensity Climbing on Performance and Muscle Oxygenation in Elite Climbers

2021 ◽  
Author(s):  
Andri Feldmann ◽  
Remo Lehmann ◽  
Frieder Wittmann ◽  
Peter Wolf ◽  
Jiří Baláš ◽  
...  
Keyword(s):  
High Intensity ◽  
Strong Association ◽  
Maximum Voluntary Contraction ◽  
Force Production ◽  
Oxidative Capacity ◽  
Acute Effect ◽  
Voluntary Contraction ◽  
Muscle Oxygenation ◽  
Control Group ◽  
Endurance Tests

AbstractHigh-intensity training (HIT) is known to have deteriorating effects on performance which manifest in various physiological changes such as lowered force production and oxidative capacity. However, the effect of HIT in climbing on finger flexor performance has not been investigated yet. Twenty-one climbers partook in an intervention study with three assessment time points: pre-HIT, post-HIT, and 24-h post-HIT. The HIT involved four five-minute exhaustive climbing tasks. Eight climbers were assigned to a control group. Assessments consisted of three finger flexor tests: maximum voluntary contraction (MVC), sustained contraction (SCT), and intermittent contraction tests (ICT). During the SCT muscle oxygenation (SmO2) metrics were collected via NIRS sensors on the forearm. The HIT had significant deteriorating effects on all force production metrics (MVC − 18%, SCT − 55%, ICT − 59%). Post-24 h showed significant recovery, which was less pronounced for the endurance tests (MVC − 3%, SCT − 16%, ICT − 22%). SmO2 metrics provided similar results for the SCT with medium to large effect sizes. Minimally attainable SmO2 and resting SmO2 both showed moderate negative correlations with pre-HIT force production respectively; r = − 0.41, P = 0.102; r = − 0.361, P = 0.154. A strong association was found between a loss of force production and change in minimally attainable SmO2 (r = − 0.734, P = 0.016). This study presents novel findings on the deteriorating effects of HIT on finger flexor performance and their oxidative capacity. Specifically, the divergent results between strength and endurance tests should be of interest to coaches and athletes when assessing athlete readiness.

scholarly journals El impacto inicial con antepié incrementa la actividad muscular del gastrocnemios durante la carrera. Un estudio cuantitativo de actividad electromiográfica (The initial impact with forefoot increases the muscular activity of gastrocnemius during running)

Retos ◽  
2020 ◽  
pp. 271-275
Author(s):  
Oscar Valencia ◽  
Iver Cristi ◽  
Dario Ahumada ◽  
Keiny Meza ◽  
Rodrigo Salas ◽  
...  
Keyword(s):  
Lower Limb ◽  
Stance Phase ◽  
Maximum Voluntary Contraction ◽  
Neuromuscular Control ◽  
Voluntary Contraction ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Myoelectric Activity ◽  
Initial Contact ◽  
Limb Injuries

Un importante porcentaje de las lesiones de miembros inferiores ha sido vinculado a la técnica de carrera, en particular, al contacto inicial con retropié (RP) o antepié (AP). Sin embargo, existe limitada evidencia de la actividad electromiográfica (EMG) para ambas condiciones. El objetivo de este estudio fue comparar la amplitud EMG en miembros inferiores al utilizar técnicas de RP vs AP durante la carrera. Trece corredores fueron evaluado a una velocidad de trote autoseleccionada en dos condiciones: contacto inicial con RP y AP. Se registró la actividad mioeléctrica del recto femoral (RF), bíceps femoral (BF), tibial anterior (TA), gastrocnemio medial (GM) y lateral (GL). Se consideró la amplitud promedio de la EMG en 10 ciclos de carrera, normalizados a la contracción voluntaria máxima. Los resultados destacan una mayor activación significativa de los músculos GM y GL en el contacto AP durante la fase de apoyo, balanceo y en todo el ciclo de carrera. Adicionalmente, el TA presentó una mayor activación durante la fase de vuelo y el 100% del ciclo de carrera para la condición RP. No se encontraron otras diferencias significativas. En conclusión, el uso de la técnica AP incrementa la actividad muscular de GM y GL, posiblemente asociado a una mayor absorción del impacto durante la fase de apoyo. Por otro lado, el TA incrementa su actividad con RP, lo que podría implicar un mayor control previo al contacto inicial. La técnica de carrera se presenta como una condición modificable según situaciones de rendimiento o patología.Abstract. Running technique has an impact on lower limb injuries, particularly the initial contact pattern such as rearfoot (RF) or forefoot (FF). However, there is limited evidence of the electromyographic (EMG) activity for both conditions. The aim of this study was to compare the lower limb muscles EMG amplitude between RF and FF techniques during running. Thirteen runners were evaluated at a self-selected running speed under two conditions: initial contact with RF and FF. The myoelectric activity of the rectus femoris (RE), biceps femoris (BF), tibialis anterior (TA), medial gastrocnemius (GM) and lateral (GL) were analysed. The EMG amplitudes of 10 running cycles were averaged and normalized to the maximum voluntary contraction. The results included a significantly higher activation of GM and GL muscles for the FF condition during the stance phase, balance and the entire running cycle. In addition, TA showed higher activation during the swing phase and the 100% running cycle for the RP condition. No other significant differences were found. In conclusion, FF technique increases GM and GL myoelectric activity, possibly associated with a higher impact absorption during the stance phase. On the other hand, TA increases its activity for RF condition which may imply a greater neuromuscular control prior to initial contact. Finally, the running technique is presented as a modifiable condition which can be changed to enhance performance or in pathologic circumstances.

scholarly journals Effect of bilateral contraction on the ability and accuracy of rapid force production at submaximal force level

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0247099
Author(s):  
Yoichi Ohta
Keyword(s):  
Grip Force ◽  
Force Production ◽  
Standing Position ◽  
Voluntary Contraction ◽  
Force Level ◽  
Noticeable Effect ◽  
Force Ratio ◽  
Significant Difference ◽  
Small Effect Size ◽  
The Difference

The present study aims to clarify the effects of bilateral contraction on the ability and accuracy of rapid force production at the submaximal force level. Eleven right-handed participants performed rapid gripping as fast and precisely as they could in unilateral (UL) and bilateral (BL) contractions in a standing position. Participants were required to impinge a grip force of 30% and 50% of their maximal voluntary contraction (MVC). Ability and accuracy of rapid force production were evaluated using the rate of force development (RFD) and force error, respectively. The data analysis did not observe a significant difference in the RFD between UL and BL contractions in both 30% (420±86 vs. 413±106%MVC/s, p = 0.34) and 50% of MVC (622±84 vs. 619±103%MVC/s, p = 0.77). Although the RFD to peak force ratio (RFD/PF) in BL contraction was lower than in UL in 30% of MVC (12.8±2.8 vs. 13.4±2.7, p = 0.003), it indicated a small effect size (d = 0.22) of the difference between UL and BL in RFD/PF. The absolute force error of BL contraction was higher than of UL contraction in 30% (4.67±2.64 vs. 3.64±1.13%MVC, p = 0.005) and 50% of MVC (5.53±2.94 vs. 3.53±0.71%MVC, p = 0.009). In addition, medium and large effect sizes were observed in absolute force error from 30% (d = 0.51) and 50% of MVC (d = 0.94), respectively. In conclusion, results indicated that the bilateral contraction reduced in the ability and accuracy of rapid force production at the submaximal force level. Nevertheless, the present results suggest that the noticeable effect of bilateral contraction is more prominent on the accuracy than in the ability of rapid force production at the submaximal force level.

scholarly journals Motor unit rate coding is severely impaired during forceful and fast muscular contractions in individuals post stroke

2013 ◽  
Vol 109 (12) ◽  
pp. 2947-2954 ◽  
Author(s):  
Li-Wei Chou ◽  
Jacqueline A. Palmer ◽  
Stuart Binder-Macleod ◽  
Christopher A. Knight
Keyword(s):  
Motor Unit ◽  
Force Production ◽  
Motor Units ◽  
Voluntary Contraction ◽  
Paretic Limb ◽  
Discharge Rates ◽  
Rate Coding ◽  
Motor Unit Action ◽  
Unit Action ◽  
Rehabilitation Strategies

Information regarding how motor units are controlled to produce forces in individuals with stroke and the mechanisms behind muscle weakness and movement slowness can potentially inform rehabilitation strategies. The purpose of this study was to describe the rate coding mechanism in individuals poststroke during both constant ( n = 8) and rapid ( n = 4) force production tasks. Isometric ankle dorsiflexion force, motor unit action potentials, and surface electromyography were recorded from the paretic and nonparetic tibialis anterior. In the paretic limb, strength was 38% less and the rate of force development was 63% slower. Linear regression was used to describe and compare the relationships between motor unit and electromyogram (EMG) measures and force. During constant force contractions up to 80% maximal voluntary contraction (MVC), rate coding was compressed and discharge rates were lower in the paretic limb. During rapid muscle contractions up to 90% MVC, the first interspike interval was prolonged and the rate of EMG rise was less in the paretic limb. Future rehabilitation strategies for individuals with stroke could focus on regaining these specific aspects of motor unit rate coding and neuromuscular activation.

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