scholarly journals Compensation for Interaction Torques During Single- and Multijoint Limb Movement

1999 ◽  
Vol 82 (5) ◽  
pp. 2310-2326 ◽  
Author(s):  
Paul L. Gribble ◽  
David J. Ostry
Keyword(s):  
Human Subjects ◽  
Emg Activity ◽  
Interaction Torque ◽  
Control Signals ◽  
Shoulder Muscles ◽  
Multijoint Movements ◽  
Movement Parameters ◽  
Shoulder Kinematics ◽  
Interaction Torques ◽  
Elbow Motion

During multijoint limb movements such as reaching, rotational forces arise at one joint due to the motions of limb segments about other joints. We report the results of three experiments in which we assessed the extent to which control signals to muscles are adjusted to counteract these “interaction torques.” Human subjects performed single- and multijoint pointing movements involving shoulder and elbow motion, and movement parameters related to the magnitude and direction of interaction torques were manipulated systematically. We examined electromyographic (EMG) activity of shoulder and elbow muscles and, specifically, the relationship between EMG activity and joint interaction torque. A first set of experiments examined single-joint movements. During both single-joint elbow ( experiment 1) and shoulder ( experiment 2) movements, phasic EMG activity was observed in muscles spanning the stationary joint (shoulder muscles in experiment 1 and elbow muscles in experiment 2). This muscle activity preceded movement and varied in amplitude with the magnitude of upcoming interaction torque (the load resulting from motion of the nonstationary limb segment). In a third experiment, subjects performed multijoint movements involving simultaneous motion at the shoulder and elbow. Movement amplitude and velocity at one joint were held constant, while the direction of movement about the other joint was varied. When the direction of elbow motion was varied (flexion vs. extension) and shoulder kinematics were held constant, EMG activity in shoulder muscles varied depending on the direction of elbow motion (and hence the sign of the interaction torque arising at the shoulder). Similarly, EMG activity in elbow muscles varied depending on the direction of shoulder motion for movements in which elbow kinematics were held constant. The results from all three experiments support the idea that central control signals to muscles are adjusted, in a predictive manner, to compensate for interaction torques—loads arising at one joint that depend on motion about other joints.

scholarly journals Dependence of EMG Responses Evoked by Imposed Wrist Displacements on Pre-existing Activity in the Stretched Muscles

1984 ◽  
Vol 11 (2) ◽  
pp. 272-280 ◽  
Author(s):  
W. Bedingham ◽  
W.G. Tatton
Keyword(s):  
Background Activity ◽  
Human Subjects ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Emg Activity ◽  
Onset Latency ◽  
Normal Human ◽  
Motoneuron Activity ◽  
Movement Parameters ◽  
The Relationship

ABSTRACT:The relationship between the segmented EMG activity in flexor carpi radialis evoked by imposed angular wrist displacement was studied with respect to the level of pre-existing background activity in 30 normal human subjects. Input-output response planes demonstrate that the magnitude of the Ml & M2-3 segments is dependent on both the displacement parameters and the level of pre-existing EMG activity in the stretched muscle. If the level of background activity exceeded 4-5% of the maximum voluntary contraction, the onset latency of the M1 segment and duration of the Ml and the M2-3 segments remained constant (within ± 2 msec) for different magnitudes of step load displacements, despite marked variation in the range of the displacement’s amplitude, duration, velocity, and acceleration. We propose that the dependency of the relationship between reflex magnitude and imposed movement parameters on tonic motoneuron activity, as represented by pre-existing EMG levels, may reflect an automatic adjustment mechanism that could be utilized in servo compensation of movements requiring markedly different force levels.

Effects of galvanic mastoid stimulation in seated human subjects

2009 ◽  
Vol 106 (3) ◽  
pp. 893-903 ◽  
Author(s):  
Z. Ghanim ◽  
J. C. Lamy ◽  
A. Lackmy ◽  
V. Achache ◽  
N. Roche ◽  
...  
Keyword(s):  
Human Subjects ◽  
Normal Subjects ◽  
Standing Position ◽  
Reflex Response ◽  
Emg Activity ◽  
Free Standing ◽  
Vestibular Response ◽  
Vestibular Reflex ◽  
Tendon Jerk ◽  
Biphasic Responses

The vestibular responses evoked by transmastoid galvanic stimulation (GS) in the rectified soleus electromyogram (EMG) in freely standing human subjects disappear when seated. However, a GS-induced facilitation of the soleus monosynaptic (H and tendon jerk) reflex has been described in few experiments in subjects lying prone or seated. This study addresses the issue of whether this reflex facilitation while seated is of vestibulospinal origin. GS-induced responses in the soleus (modulation of the rectified ongoing EMG and of the monosynaptic reflexes) were compared in the same normal subjects while freely standing and sitting with back and head support. The polarity-dependent biphasic responses in the free-standing position were replaced by a non-polarity-dependent twofold facilitation while seated. The effects of GS were hardly detectable in the rectified ongoing voluntary EMG activity, weak for the H reflex, but large and constant for the tendon jerk. They were subject to habituation. Anesthesia of the skin beneath the GS electrodes markedly reduced the reflex facilitation, while a similar, although weaker, facilitation of the tendon jerk was observed when GS was replaced with purely cutaneous stimulation, a tap to the tendon of the sternomastoid muscle, or an auditory click. The stimulation polarity independence of the GS-induced reflex facilitation argues strongly against a vestibular response. However, the vestibular afferent volley, insufficient to produce a vestibular reflex response while seated, could summate with the GS-induced tactile or proprioceptive volley to produce a startle-like response responsible for the reflex facilitation.

scholarly journals Control Strategies for the Transition From Multijoint to Single-Joint Arm Movements Studied Using a Simple Mechanical Constraint

2000 ◽  
Vol 83 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Robert A. Scheidt ◽  
W. Zev Rymer
Keyword(s):  
Control Strategies ◽  
Human Subjects ◽  
Dynamic Performance ◽  
Activity Patterns ◽  
Adaptive Controller ◽  
Emg Activity ◽  
Joint Control ◽  
Primary Role ◽  
Joint Task ◽  
Normal Human

Changes were studied in neuromotor control that were evoked by constraining the motion of the elbow joint during planar, supported movements of the dominant arm in eight normal human subjects. Electromyograph (EMG) recordings from shoulder and arm muscles were used to determine whether the normal multijoint muscle activity patterns associated with reaching to a visual target were modified when the movement was reduced to a single-joint task, by pinning the elbow to a particular location in the planar work space. Three blocks of 150 movements each were used in the experiments. Subjects were presented with the unconstrained task in the first and third blocks with an intervening block of constrained trials. Kinematic, dynamic, and EMG measures of performance were compared across blocks. The imposition of the pin constraint caused predictable changes in kinematic performance, in that near-linear motions of the hand became curved. This was followed by changes in limb dynamic performance at the elbow. However, changes in EMG activity at the shoulder lagged the kinematic changes substantially (by about 15 trials). The gradual character of the changes in EMG timing does not support a primary role for segmental reflex action in mediating the transition between multijoint and single-joint control strategies. Furthermore, the scope and magnitude of these changes argues against the notion that human motor performance is driven by the optimization of muscle- or joint-related criteria alone. The findings are best described as reflecting the actions of a feedforward adaptive controller that has properties that are modified progressively according to the environmental state.

Electrical Activity from the Superior Pharyngeal Constrictor During Reflexive and Nonreflexive Tasks

1989 ◽  
Vol 32 (4) ◽  
pp. 749-754 ◽  
Author(s):  
Adrienne L. Perlman ◽  
Erich S. Luschei ◽  
Charles E. Du Mond
Keyword(s):  
Electrical Activity ◽  
Healthy Subjects ◽  
General Trend ◽  
Human Subjects ◽  
Electrode Placement ◽  
Emg Activity ◽  
Constrictor Muscle ◽  
Natural Logarithm ◽  
Quantitative Manner ◽  
Normal Human

The purpose of this investigation was to determine, in a quantitative manner, which, if any, nonswallowing tasks produce significant levels of activation in the superior pharyngeal constrictor muscle of normal human subjects. Bipolar hooked wire electrodes were inserted in the superior pharyngeal constrictor muscle of 15 healthy subjects. Electrode placement was controlled. Each subject performed two reflexive tasks, six voluntary tasks requiring phonation, and four nonspeech voluntary tasks. The electromyogram (EMG) was rectified and integrated. The resulting number was then transformed by taking its natural logarithm. An ANOVA was performed and a linear model was estimated. The magnitude of the EMG activity was related to the location of the electrodes. The largest values were recorded in the lateral-superior placement, followed by the lateral-inferior, medial-inferior and medial-superior. The superior pharyngeal contrictor was found to be a muscle activated primarily during reflexive activity. There was a general trend in the amplitude of EMG activity in relationship to task. Swallowing produced the greatest amount of activity and a gag produced about 60% of the activity produced by the swallow. Two tasks, production of the work /hk/ in which the phoneme /k/ was stressed, and a "modified Valsalva," which was actually a hard /k/ held for several seconds, produced the next greatest level of EMG.

Use of a Shoulder Rest for Playing the Violin Revisited: An Analysis of the Effect of Shoulder Rest Height on Muscle Activity, Violin Fixation Force, and Player Comfort

2019 ◽  
Vol 34 (1) ◽  
pp. 39-46 ◽  
Author(s):  
Laura M Kok ◽  
Jim Schrijvers ◽  
Marta Fiocco ◽  
Barend van Royen ◽  
Jaap Harlaar
Keyword(s):  
Muscle Activity ◽  
Anterior Part ◽  
Activity Patterns ◽  
Deltoid Muscle ◽  
Surface Emg ◽  
Emg Activity ◽  
Linear Regression Models ◽  
Upper Trapezius ◽  
Shoulder Muscles ◽  
Rest Condition

AIMS: For violinists, the shoulder rest is an ergonomic adaptation to reduce musculoskeletal load. In this study, we aimed to evaluate how the height of the shoulder rest affects the violin fixation force and electromyographic (EMG) activity of the superficial neck and shoulder muscles. METHODS: In professional violinists, four different shoulder rest heights during five playing conditions were evaluated. Outcome variables included the jaw-shoulder violin fixation force and bilateral surface EMG of the upper trapezius (mTP), sternocleidomastoid (mSCM), and left anterior part of the left deltoid muscle (mDTA). Playing comfort was subjectively rated on a visual analogue scale (VAS). Linear regression models were estimated to investigate the influence of the shoulder rest height on muscle activity and violin fixation force as well as the muscle activity of the five evaluated muscles on violin fixation force. RESULTS: 20 professional violinists (4 males, 16 females, mean age 29.4 yrs) participated in this study. The shoulder rest condition had a significant effect on playing comfort (p<0.001), with higher shoulder rest conditions associated with decreased subjective playing comfort. The mean violin fixation force for each shoulder rest condition ranged between 2.92 and 3.39 N; higher shoulder rests were related to a higher violin fixation force (p<0.001). CONCLUSION: In this study, violin fixation force and muscle activity of the left mDTA increased while playing with an increasing height of the shoulder rest. As the shoulder rest influences muscle activity patterns and violin fixation force, adjustment of the shoulder rest and positioning of the violin need to be carefully optimized.

Fast corrective responses are evoked by perturbations approaching the natural variability of posture and movement tasks

2012 ◽  
Vol 107 (10) ◽  
pp. 2821-2832 ◽  
Author(s):  
F. Crevecoeur ◽  
I. Kurtzer ◽  
S. H. Scott
Keyword(s):  
Motor Tasks ◽  
Small Perturbations ◽  
Voluntary Motor ◽  
Intersegmental Dynamics ◽  
Shoulder Muscles ◽  
Long Latency ◽  
Evoked Activity ◽  
Perturbation Magnitude ◽  
Elbow Motion ◽  
Muscle Responses

A wealth of studies highlight the importance of rapid corrective responses during voluntary motor tasks. These studies used relatively large perturbations to evoke robust muscle activity. Thus it remains unknown whether these corrective responses (latency 20–100 ms) are evoked at perturbation levels approaching the inherent variability of voluntary control. To fill this gap, we examined responses for large to small perturbations applied while participants either performed postural or reaching tasks. To address multijoint corrective responses, we induced various amounts of single-joint elbow motion with scaled amounts of combined elbow and shoulder torques. Indeed, such perturbations are known to elicit a response at the unstretched shoulder muscle, which reflects an internal model of arm intersegmental dynamics. Significant muscle responses were observed during both postural control and reaching, even when perturbation-related joint angle, velocity, and acceleration overlapped in distribution with deviations encountered in unperturbed trials. The response onsets were consistent across the explored range of perturbation loads, with short-latency onset for the muscles spanning the elbow joints (20–40 ms), and long-latency for shoulder muscles (onset > 45 ms). In addition, the evoked activity was strongly modulated by perturbation magnitude. These results suggest that multijoint responses are not specifically engaged to counter motor errors that exceed a certain threshold. Instead, we suggest that these corrective processes operate continuously during voluntary motor control.

scholarly journals A comprehensive assessment of genioglossus electromyographic activity in healthy adults

2015 ◽  
Vol 113 (7) ◽  
pp. 2692-2699 ◽  
Author(s):  
Jennifer R. Vranish ◽  
E. Fiona Bailey
Keyword(s):  
Fiber Type ◽  
Human Subjects ◽  
Body Position ◽  
Critical Role ◽  
Emg Activity ◽  
Electromyographic Activity ◽  
Quarter Century ◽  
Airway Patency ◽  
Human Tongue ◽  
Electrode Recording

The genioglossus (GG) is an extrinsic muscle of the human tongue that plays a critical role in preserving airway patency. In the last quarter century, >50 studies have reported on respiratory-related GG electromyographic (EMG) activity in human subjects. Remarkably, of the studies performed, none have duplicated subject body position, electrode recording locations, and/or breathing task(s), making interpretation and integration of the results across studies extremely challenging. In addition, more recent research assessing lingual anatomy and muscle contractile properties has identified regional differences in muscle fiber type and myosin heavy chain expression, giving rise to the possibility that the anterior and posterior regions of the muscle fulfill distinct functions. Here, we assessed EMG activity in anterior and posterior regions of the GG, across upright and supine, in rest breathing and in volitionally modulated breathing tasks. We tested the hypotheses that GG EMG is greater in the posterior region and in supine, except when breathing is subject to volitional modulation. Our results show differences in the magnitude of EMG (%regional maximum) between anterior and posterior muscle regions (7.95 ± 0.57 vs. 11.10 ± 0.99, respectively; P < 0.001), and between upright and supine (8.63 ± 0.73 vs. 10.42 ± 0.90, respectively; P = 0.008). Although the nature of a task affects the magnitude of EMG ( P < 0.001), the effect is similar for anterior and posterior muscle regions and across upright and supine ( P > 0.2).

scholarly journals Muscle Activation During Selected Strength Exercises in Women With Chronic Neck Muscle Pain

2008 ◽  
Vol 88 (6) ◽  
pp. 703-711 ◽  
Author(s):  
Lars L Andersen ◽  
Michael Kjær ◽  
Christoffer H Andersen ◽  
Peter B Hansen ◽  
Mette K Zebis ◽  
...  
Keyword(s):  
Clinical Diagnosis ◽  
Muscle Pain ◽  
Muscle Activation ◽  
Trapezius Muscle ◽  
Emg Activity ◽  
Neck Muscle ◽  
Electromyographic Activity ◽  
Trapezius Myalgia ◽  
Shoulder Muscles ◽  
Strength Exercises

Background and PurposeMuscle-specific strength training has previously been shown to be effective in the rehabilitation of chronic neck muscle pain in women. The aim of this study was to determine the level of activation of the neck and shoulder muscles using surface electromyography (EMG) during selected strengthening exercises in women undergoing rehabilitation for chronic neck muscle pain (defined as a clinical diagnosis of trapezius myalgia).SubjectsThe subjects were 12 female workers (age=30–60 years) with a clinical diagnosis of trapezius myalgia and a mean baseline pain intensity of 5.6 (range=3–8) on a scale of 0 to 9.MethodElectromyographic activity in the trapezius and deltoid muscles was measured during the exercises (lateral raises, upright rows, shrugs, one-arm rows, and reverse flys) and normalized to EMG activity recorded during a maximal voluntary static contraction (MVC).ResultsFor most exercises, the level of muscle activation was relatively high (&gt;60% of MVC), highlighting the effectiveness and specificity of the respective exercises. For the trapezius muscle, the highest level of muscle activation was found during the shrug (102±11% of MVC), lateral raise (97±6% of MVC), and upright row (85±5% of MVC) exercises, but the latter 2 exercises required smaller training loads (3–10 kg) compared with the shrug exercise (20–30 kg).Discussion and ConclusionThe lateral raise and upright row may be suitable alternatives to shrugs during rehabilitation of chronic neck muscle pain. Several of the strength exercises had high activation of neck and shoulder muscles in women with chronic neck pain. These exercises can be used equally in the attempt to achieve a beneficial treatment effect on chronic neck muscle pain.

Spinal reciprocal inhibition in human locomotion

2004 ◽  
Vol 96 (5) ◽  
pp. 1969-1977 ◽  
Author(s):  
Aiko Kido ◽  
Naofumi Tanaka ◽  
Richard B. Stein
Keyword(s):  
Nerve Stimulation ◽  
Tibial Nerve ◽  
Human Subjects ◽  
Tibialis Anterior Muscle ◽  
Reciprocal Inhibition ◽  
Emg Activity ◽  
Healthy Human ◽  
Fast Walking ◽  
Tibial Nerve Stimulation ◽  
The Difference

The purpose of this paper was to study spinal inhibition during several different motor tasks in healthy human subjects. The short-latency, reciprocal inhibitory pathways from the common peroneal (CP) nerve to the soleus muscle and from the tibial nerve to the tibialis anterior muscle were studied as a depression of ongoing voluntary electromyograph (EMG) activity. First, the effect of stimulus intensity on the amount of inhibition was examined to decide an appropriate stimulation to study the task-dependent modulation of inhibition. Then, the inhibition at one level of stimulation (1.5 × motor threshold) was investigated during standing, walking, and running. The change in slope of inhibition vs. EMG level, which approximates the fraction of ongoing activity that is inhibited, decreased with CP stimulation from 0.52 during standing to 0.30 during fast walking (6 km/h) to 0.17 during running at 9 km/h. Similarly, the slope decreased with tibial nerve stimulation from 0.68 (standing) to 0.42 (fast walking) to 0.35 (running at 9 km/h). All differences, except the last one, were highly significant ( P < 0.01, Student's t-test). However, the difference between walking (0.42) and running (0.36) at the same speed (6 km/h) was not significant with tibial nerve stimulation and only significant at P < 0.05 with CP nerve stimulation (0.30, 0.20). Also, the difference between standing (0.52) and slow walking (3 km/h; 0.41) with CP stimulation was not significant, but it was significant ( P < 0.01) with tibial nerve stimulation (0.68, 0.49). In conclusion, our findings indicate that spinal reciprocal inhibition decreases substantially with increasing speed and only changes to a lesser extent with task.

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