Postural adjustments associated with rapid voluntary arm movements 1. Electromyographic data (original) (raw)
Related papers
Goal-directed arm movements: I. Analysis of EMG records in shoulder and elbow muscles
Journal of Electromyography and Kinesiology, 1992
The coordinated control of shoulder and elbow muscles during goaldirected arm movements has been studied. Timing and amplitude of the electromyographic activity of 13 muscles and muscle parts have been analyzed. Triphasic alternating agonist-antagonist activity commonly associated with acceleration and deceleration of the limb has been found in eight shoulder muscles or muscle parts. Of these muscles, the pectoralis major (pars clavicularis), the deltoideus (pars anterior and posterior), and the latissimus dorsi act on the humerus and can be regarded as prime movers of the upper arm. The serratus anterior and the trapezius (pars descendens, transversalis, and ascendens) act on the scapula. In these scapular muscles, agonist activity similar to that in the prime movers has been found. This indicates an important role of scapular muscles during acceleration of the arm. Significant differences in timing between synergist muscles have been demonstrated: Activity of the latissimus dorsi precedes the deltoideus pars posterior by up to 62 ms. Only minor differences in timing were observed between scapular muscles and prime movers. In biarticular (shoulder and elbow) muscles and in muscles acting only on the elbow, continued activity has been observed throughout the movement. This activity yielded coactivation of functional antagonist muscles. The movement direction in which the largest activity occurred is consistent with the function of overcoming a resistance in the elbow resulting from the cocontraction found.
Gait & Posture, 2008
To elucidate the effect on movement-related potentials (MRPs) of anticipatory postural adjustments (APAs) accompanied by voluntary focal movement, we examined the MRPs of shoulder flexion movement under standing and sitting postural conditions in 12 normal subjects. MRPs were evaluated based on three components: readiness potential (RP), motor potential (MP), and movement-monitoring potential. APAs were observed in the activities of postural muscles including the biceps femoris and erector spinae muscles only under standing conditions. The amplitudes of the three MRP components were larger under standing conditions than under sitting conditions for all recorded electrode positions, and the RP and MP amplitudes at the vertex position, which lies over the supplementary motor area (SMA), showed a prominent increase under standing conditions with the highest statistical significance. These results suggest that a recruited neural process of the cortical area including the SMA may be necessary to generate voluntary movement accompanied by APA. #
Experimental Brain Research, 2008
The hypothesis that anticipatory postural adjustments (APAs) may concur in generating the directional preference experienced during limb coupled movements was tested by measuring the electromyographic and mechanic postural actions elicited when moving: i) one single arm/hand and, ii) both limbs, iso-or antidirectionally coupled. During fast adduction of the right arm in the horizontal plane (prime mover, pectoralis Major, RPM) APAs were recorded in the contralateral LPM as well as in the right ischiocruralis (RIC) muscle. This last action was associated to a transient increase of Tz (torque around body vertical axis) in the direction opposite to arm rotation. Both the APAs in RIC and the Tz changes nearly doubled in size when arms were coupled isodirectionally (adduction of one arm and abduction on the other) while they vanished when both arms were simultaneously adducted (antidirectional coupling). Conformably, during rhythmic arm oscillations APAs and Tz were cyclically modulated when movements were isodirectional, the modulation amplitude being strongly enhanced by increasing the movement frequency. When oscillations were antidirectional neither APAs nor Tz changes were observed, even if frequency was incremented. The postural actions linked to unidirectional or cyclic movements of the hand were affected by either coupling or frequency in the same way as arm movements, albeit much smaller in size In conclusion, during antidirectional movements APAs in prime movers are synergic with voluntary activation and no postural engagement is requested to leg muscles. Conversely, during isodirectional movements, APAs in prime movers conflict with the voluntary commands and a strong, frequency dependent, postural effort is required to leg muscles. How these factors may cooperate in determining the preference for antidirectional coupling is discussed.
European Journal of Applied Physiology and Occupational Physiology, 1990
The electromyographical (EMG) response to isometric ramp contractions of the fight arm, the left arm, and both arms was studied using four pairs of surface electrodes above the right upper trapezius muscle (UT) of six men and six women. Contractions were made against gravity with the active arm(s) in eight positions, ranging from flexion to abduction. To describe arm positions, a new, simple terminology was developed. Root mean square (rms)-converted EMG-signals were normalized (EMG .... ) with respect to a reference contraction. The EMG .... corresponding to a 15 N.m torque in the fight glenohumeral (GH) joint was strongly related to the position of the fight arm (P< 0.001). The shape of this relationship depended on the electrode position (P<0.001). The ratio between EMG .... at 30 N.m and 15 N.m GH torques was related to arm position (P< 0.001) and differed between electrodes (P< 0.001). A left-side GH torque resulted in fight-side (contralateral) EMG activity, typically corresponding to 20%-30% of that obtained during similar fight-side GH torque. Bilateral GH torque implied 0%-50% increase in EMG activity as compared to that obtained with the fight arm alone. The results have shown that signals from one pair of surface electrodes above UT cannot be taken as representative of the EMG activity from electrodes located elsewhere above UT. The EMG recordings reflected a complex pattern of muscular activation, significantly related to both outwardly visible factors (arm position, GH torque), and withinbody servosystems (motor control reflexes).
Postural Dependence of Muscle Actions: Implications for Neural Control
The Journal of Neuroscience, 1997
The neural control of reaching entails the specification of a precise pattern of muscle activation distributed across the many muscles of the arm. Musculoskeletal geometry limits the possible solutions to this problem. Insight into the nature of this constraint was obtained by quantifying the postural variation in the mechanical actions of six human shoulder muscles. Estimates of muscle mechanical actions were obtained by electrically stimulating muscles to the point of contraction and recording the resulting forces and torques with a six-degree-of-freedom force-torque transducer. In a given experiment, data were obtained for up to 29 different arm postures. The mechanical actions of each muscle varied systematically with arm posture, regardless of the frame of reference used to define these actions. The nature of this dependence suggests that a relatively simple strategy can be used by the nervous system to account for the changing mechanical actions of arm muscles.
Experimental Brain Research, 2008
While sitting on a turnable stool, with both shoulder flexed at 90° or, alternatively, with arms parallel to the trunk and the elbow flexed at 90°-the hands being semisupine-subjects performed unidirectional and cyclic movements on the horizontal plane of the right arm (adduction and abduction) or hand (flexion-extension). The left arm was still, in a position symmetrical to that of the right limb and with the hand contacting a fixed support by the palmar or dorsal surface. During both unidirectional and cyclic arm or hand movements, activation of the prime mover muscles (right Pectoralis Major for arm adduction and Infraspinatus for abduction; right Flexor Carpi Radialis and Extensor Carpi Radialis for the hand movements) was accompanied by activation of the homologous muscles of the contralateral arm and inhibition of antagonists. The contralateral activities 1) regularly preceded the burst in the movement prime movers and 2) were organised in fixation chains that, exerting forces on the hand fixed support, will counterbalance the rotatory action exerted on the trunk by the primary movement. Based on these features, these activities may be classified as Anticipatory Postural Adjustments (APAs). The observed APAs distribution is such as to favour the preferential (mirror symmetrical) coupling of upper limb movements on the horizontal plane. The possible role of these APAs in determining the different constraints experienced when performing mirror symmetrical versus isodirectional coupling is discussed.
Electromyographic response of the trunk muscles to postural perturbation in sitting subjects
Journal of Electromyography and Kinesiology, 1998
Electromyographic (EMG) patterns of the trunk muscles were investigated during balance perturbations in a sitting position. Five healthy subjects (two females and three males, mean age 24.4 yr) were seated on a platform allowing rotational perturbations in the frontal and sagittal planes. Each of the forward, backward, right and left perturbations were delivered with and without expectation at the velocities 8°s Ϫ 1 (SD ± 4°s Ϫ 1 ) and 26°s Ϫ 1 (SD ± 6°s Ϫ 1 ). The fast expected and unexpected perturbations were compared in blindfolded subjects. In the slow perturbations the effect of a blindfold on the balance reactions was tested. The root mean square (RMS) EMG signals from 12 trunk muscles were recorded and analysed to determine the EMG magnitudes. During the forward and backward rotations there was always a symmetrical EMG pattern between corresponding muscles on the right and left sides. A reciprocal phasic EMG activity between the left and right back muscles was found during frontal rotations. No reciprocal phasic activity was found in the abdominal muscles. Neither verbal instruction about the upcoming perturbation nor the blindfold changed the activation patterns.
Influence of stimulus parameters on human postural responses. J. Neurophysiol
Journal of Neurophysiology
AND CONCLUSIONS 1. The role of sensory information in shaping muscle activation patterns to postural perturbations in humans was investigated by varying velocity, amplitude, or duration of the perturbing stimulus. Ten normal subjects were exposed to 120 backward translations of the support surface under conditions of varying velocities ( 1 O-35 cm/s, constant amplitude), varying amplitudes (1.2-12 cm, constant velocity), or varying durations (40-800 ms). The effects of perturbation parameters on movement kinematics and EMG latencies, patterns, and integrated areas in six trunk and leg muscles were examined. Integrated EMG activity was normalized across subjects and the early (first 75 ms), middle (second 75 ms), and late (last 350 ms) components were analyzed separately.
The effect of the amplitude of motor action on anticipatory postural adjustments
Journal of Electromyography and Kinesiology, 2004
The purpose of this study was to determine whether changes in the amplitude of a motor action triggering the same perturbation affect anticipatory postural adjustments (APAs). Healthy subjects performed releases of the same load with shoulder abduction movements of different amplitudes. Changes in the electrical activity of trunk and leg muscles, as well as displacements of the center of pressure were recorded. Generally, there were no differences in anticipatory activity of muscles and displacements of the center of pressure between series of load releases induced by motor actions of different amplitudes. We suggest that the CNS arranges APAs based on the magnitude of the perturbation if the same muscle groups generate motor actions of different amplitudes. #