scholarly journals Effects of assistive force on the agonist and antagonist muscles in elbow flexion

2017 ◽  
Vol 6 (2) ◽  
Author(s):  
Nursalbiah Nasir ◽  
Keisuke Hayashi ◽  
Ping Yeap Loh ◽  
Satoshi Muraki
Keyword(s):  
Muscle Contraction ◽  
Perceived Exertion ◽  
Elbow Flexion ◽  
Emg Activity ◽  
Antagonist Muscle ◽  
Isometric Muscle Contraction ◽  
Antagonist Muscles ◽  
Agonist And Antagonist ◽  
Agonist And Antagonist Muscles ◽  
Isometric Muscle

This study investigated the responses of the agonist and antagonist muscles against assistive force during isometric muscle contraction. Participants performed isometric elbow flexion at 90º for 30 seconds under two workload conditions (20% and 40% of the maximal voluntary workload) with three levels of assistive force (0%, 50%, and 100% theoretical effectiveness) for 10 seconds. Electromyography (EMG) of the biceps (agonist muscle) and triceps (antagonist muscle) was measured during the task, and perceived exertion was obtained after the task. Assistive force significantly reduced EMG activity in the agonist muscle and the perceived exertion score only at 40% workload. However, the reduction of EMG activity and perceived exertion score were lower than that for the physical estimated effect. In addition, the EMG activity in the antagonist muscle was not influenced, irrespective of workload conditions and the level of assistive force. These results suggested that although the assistive force during isometric muscle contraction relieves exertion of the agonist muscle that accompanies the decrease in perceived exertion, their assistive effects are influenced by various human physiological and anatomical factors. 

Neck Muscle Responses to Stimulation of Monkey Superior Colliculus. II. Gaze Shift Initiation and Volitional Head Movements

2002 ◽  
Vol 88 (4) ◽  
pp. 2000-2018 ◽  
Author(s):  
Brian D. Corneil ◽  
Etienne Olivier ◽  
Douglas P. Munoz
Keyword(s):  
Superior Colliculus ◽  
Neck Muscles ◽  
Head Movements ◽  
Emg Activity ◽  
Neck Muscle ◽  
Gaze Shift ◽  
Antagonist Muscles ◽  
Agonist And Antagonist ◽  
Agonist And Antagonist Muscles ◽  
Stimulation Of

We report neck muscle activity and head movements evoked by electrical stimulation of the superior colliculus (SC) in head-unrestrained monkeys. Recording neck electromyography (EMG) circumvents complications arising from the head's inertia and the kinetics of muscle force generation and allows precise assessment of the neuromuscular drive to the head plant. This study served two main purposes. First, we sought to test the predictions made in the companion paper of a parallel drive from the SC onto neck muscles. Low-current, long-duration stimulation evoked both neck EMG responses and head movements either without or prior to gaze shifts, testifying to a SC drive to neck muscles that is independent of gaze-shift initiation. However, gaze-shift initiation was linked to a transient additional EMG response and head acceleration, confirming the presence of a SC drive to neck muscles that is dependent on gaze-shift initiation. We forward a conceptual neural architecture and suggest that this parallel drive provides the oculomotor system with the flexibility to orient the eyes and head independently or together, depending on the behavioral context. Second, we compared the EMG responses evoked by SC stimulation to those that accompanied volitional head movements. We found characteristic features in the underlying pattern of evoked neck EMG that were not observed during volitional head movements in spite of the seemingly natural kinematics of evoked head movements. These features included reciprocal patterning of EMG activity on the agonist and antagonist muscles during stimulation, a poststimulation increase in the activity of antagonist muscles, and synchronously evoked responses on agonist and antagonist muscles regardless of initial horizontal head position. These results demonstrate that the electrically evoked SC drive to the head cannot be considered as a neural replicate of the SC drive during volitional head movements and place important new constraints on the interpretation of electrically evoked head movements.

scholarly journals Biomechanics of Submaximal Recumbent Cycling in Adolescents With and Without Cerebral Palsy

2007 ◽  
Vol 87 (5) ◽  
pp. 572-585 ◽  
Author(s):  
Therese E Johnston ◽  
Ann E Barr ◽  
Samuel CK Lee
Keyword(s):  
Cerebral Palsy ◽  
Motor Control ◽  
Energy Expenditure ◽  
Muscle Activity ◽  
Perceived Exertion ◽  
Circular Data ◽  
Typical Development ◽  
Antagonist Muscles ◽  
Agonist And Antagonist ◽  
Agonist And Antagonist Muscles

Background and Purpose The purpose of this study was to compare the biomechanics of recumbent cycling between adolescents with cerebral palsy (CP) classified at Gross Motor Function Classification System (GMFCS) levels III and IV and adolescents with typical development (TD). Subjects Twenty subjects, ages (X̄±SD) 15.2±1.6 years (10 with TD, 10 with CP), participated. Methods Lower-extremity kinematics and muscle activity were measured at 30 and 60 rpm while subjects pedaled on a recumbent cycle. Energy expenditure and perceived exertion were measured during a 5-minute test, and efficiency was calculated. Noncircular data were analyzed with analyses of variance. Circular data were analyzed using circular t tests. Results Differences were found between groups for joint kinematics for all motions. Subjects with CP displayed earlier onsets and later offsets of muscle activity, increased co-contraction of agonist and antagonist muscles, and decreased efficiency compared with subjects with TD. There were no differences in perceived exertion. Discussion and Conclusion Differences in cycling biomechanics between children with CP and children with TD may be due to decreased strength and motor control in the children with CP.

Coactivation of the antagonist muscle does not covary with steadiness in old adults

2000 ◽  
Vol 89 (1) ◽  
pp. 61-71 ◽  
Author(s):  
Rebecca A. Burnett ◽  
Douglass H. Laidlaw ◽  
Roger M. Enoka
Keyword(s):  
Index Finger ◽  
Constant Load ◽  
Left Index Finger ◽  
Antagonist Muscle ◽  
Lengthening Contractions ◽  
Old Adults ◽  
Antagonist Muscles ◽  
Agonist And Antagonist ◽  
Shortening Contractions ◽  
Agonist And Antagonist Muscles

The purpose of the study was to determine the association between steadiness and activation of the agonist and antagonist muscles during isometric and anisometric contractions. Young ( n = 14) and old ( n = 15) adults used the first dorsal interosseus muscle to perform constant-force and constant-load tasks (2.5, 5, 20, 50, and 75% maximum) with the left index finger. Steadiness was quantified as the coefficient of variation of force and the SD of acceleration normalized to the load lifted. The old adults were less steady at most target forces with isometric contractions (2.5, 5, and 50%) and with most loads during the anisometric contractions (2.5, 5, and 20%). Furthermore, the old adults were less steady when performing lengthening contractions (up to 50%) compared with shortening contractions, whereas there was no difference for young adults. The reduced steadiness exhibited by the old adults during these tasks was not associated with differences in the average level of agonist muscle electromyogram or with coactivation of the antagonist muscle.

scholarly journals Actomyosin energy turnover declines while force remains constant during isometric muscle contraction

2004 ◽  
Vol 555 (1) ◽  
pp. 27-43 ◽  
Author(s):  
Timothy G. West ◽  
N. A. Curtin ◽  
Michael A. Ferenczi ◽  
Zhen-He He ◽  
Yin-Biao Sun ◽  
...  
Keyword(s):  
Muscle Contraction ◽  
Energy Turnover ◽  
Isometric Muscle Contraction ◽  
Isometric Muscle
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