Reciprocal effect of single corticomotoneuronal cells on wrist extensor and flexor muscle activity in the primate

1982 ◽  
Vol 247 (1) ◽  
pp. 164-168 ◽  
Author(s):  
Paul D. Cheney ◽  
Richard Kasser ◽  
James Holsapple
Keyword(s):  
Muscle Activity ◽  
Flexor Muscle ◽  
Reciprocal Effect ◽  
Wrist Extensor ◽  
Corticomotoneuronal Cells

Evaluation of an adjustable support shoulder exoskeleton on static and dynamic overhead tasks

2018 ◽  
Vol 62 (1) ◽  
pp. 804-808 ◽  
Author(s):  
Logan Van Engelhoven ◽  
Nathan Poon ◽  
Homayoon Kazerooni ◽  
Alan Barr ◽  
David Rempel ◽  
...  
Keyword(s):  
Muscle Activity ◽  
Muscle Activation ◽  
Peak Torque ◽  
Industrial Workers ◽  
Human Engineering ◽  
Shoulder Injuries ◽  
Flexor Muscle ◽  
Work Related ◽  
Upper Trapezius ◽  
Shoulder Complex

Introduction: Overhead tasks increase the risk of work related musculoskeletal disorders to industrial workers. A shoulder supporting exoskeleton with adjustable and angle dependent torque (referred to as shoulderX in this paper for brevity) was designed and built at the University of California Berkeley Human Engineering and Robotics Laboratory for workers performing overhead tasks. shoulderX was designed specifically to reduce the exposure to large muscle exertion forces on the shoulder complex from overhead work. Methods: We evaluated shoulderX by measuring the muscle activation of the upper trapezius (UT), anterior deltoid (AD), triceps long head (TR), and infraspinatus (IF) during static and dynamic overhead tasks. Thirteen male subjects with experience in the construction or manufacturing industries were recruited to perform overhead tasks using light (.45 kg) and heavy (2.25 kg) weight tools with four exoskeleton support levels (0, 8.5, 13.0, 20.0 Nm peak torque). Results: During all conditions, the wearer’s shoulder flexor muscle activity of UT, AD were reduced with increasing strength of shoulderX by up to 80%. Subjects unanimously preferred the use of shoulderX over the unassisted condition for all task types (static and dynamic overhead tasks) and tool weights (.45 kg and 2.25 kg). Conclusion: shoulderX reduces the wearer’s primary muscle activity in overhead static and dynamic work and results in a more desirable and balanced pattern of shoulder complex activation. This investigation indicates that shoulderX reduces the risk of work related shoulder injuries during overhead tasks.

Wrist Splint Effects on Muscle Activity and Force during a Handgrip Task

2008 ◽  
Vol 24 (3) ◽  
pp. 298-303 ◽  
Author(s):  
Jennifer Di Domizio ◽  
Jeremy P.M. Mogk ◽  
Peter J. Keir
Keyword(s):  
Muscle Activity ◽  
Extensor Muscle ◽  
External Loading ◽  
Wrist Motion ◽  
Wrist Extensor ◽  
Custom Made ◽  
Flexor Muscles ◽  
Light Activity ◽  
Extensor Carpi Radialis ◽  
Wrist Splint

Wrist splints are commonly prescribed to limit wrist motion and provide support at night and during inactive periods but are often used in the workplace. In theory, splinting the wrist should reduce wrist extensor muscle activity by stabilizing the joint and reducing the need for co-contraction to maintain posture. Ten healthy volunteers underwent a series of 24 10-s gripping trials with surface electromyography on 6 forearm muscles. Trials were randomized between splinted and nonsplinted conditions with three wrist postures (30° flexion, neutral, and 30° extension) and four grip efforts. Custom-made Plexiglas splints were taped to the dorsum of the hand and wrist. It was found that when simply holding the dynamometer, use of a splint led to a small (<1% MVE) but significant reduction in activity for all flexor muscles and extensor carpi radialis (all activity <4% maximum). At maximal grip, extensor muscle activity was significantly increased with the splints by 7.9–23.9% MVE. These data indicate that splinting at low-to-moderate grip forces may act to support the wrist against external loading, but appears counterproductive when exerting maximal forces. Wrist bracing should be limited to periods of no to light activity and avoided during tasks that require heavy efforts.

Electromyographic Responses to Affective Visual Stimulation

1971 ◽  
Vol 33 (3) ◽  
pp. 755-758
Author(s):  
Douglas Carroll
Keyword(s):  
Muscle Activity ◽  
Visual Stimulation ◽  
Visual Stimuli ◽  
Flexor Muscle ◽  
Extensor Muscles ◽  
Affective Visual Stimuli

EMGs from flexor and extensor muscles were recorded during the presentation of affective visual stimuli. Dominant flexor muscle activity was observed with unpleasant visual stimuli. Extensor EMG was not differentially influenced by stimuli of different affect.

scholarly journals Advanced Rock Climbers Exhibit Greater Finger Force and Resistance to Fatigue Compared to Novices During Treadwall Climbing

2020 ◽  
Author(s):  
Philip F. Ferrara ◽  
James Becker ◽  
John G. Seifert
Keyword(s):  
Muscle Activity ◽  
Force Plate ◽  
Force Production ◽  
Median Frequency ◽  
Finger Force ◽  
Flexor Muscle ◽  
Significant Group ◽  
Maximum Voluntary Isometric Contraction ◽  
Before And After ◽  
Flexor Digitorum

AbstractBackgroundThe purpose of the study was to investigate the effects of rock climbing experience on time to fatigue (TTF), finger flexor force production relative to body weight (REL FP), and changes in finger flexor muscle activity during tread wall climbing.MethodsEight advanced and seven novice sport rock climbers performed a climbing protocol on a treadwall system. The protocol consisted of climbing for six 5-minute intervals or until voluntary failure. A mounted force plate was used to measure finger force production before and after the climbing protocol. Subjects performed a 20-second maximum voluntary isometric contraction (MVIC) against the force plate with the dominant and non-dominant fingertips in a common climbing hand configuration known as a half crimp. Muscle activity was monitored with electromyographic electrodes placed bilaterally over the subject’s flexor digitorum superficialis. Median frequency (MF) and root mean square (RMS) were analyzed. The treadwall was set at a difficulty of 9 IRCRA/5.9 YDS. It rotated at 7 m/min and was fixed at 7° overhanging.ResultsSignificant group differences were observed in subject characteristics, TTF (30±0 vs. 25.7±3.6 min), REL FP (5.6±1.2 vs. 3.2±0.9 N/kg BW), ΔFP (+1.5±12.3% vs. -31±16%), and ΔMF (+6.3±22.4% vs. -17.6±10.9%).ConclusionThe results of this study demonstrate that advanced climbers possess greater finger flexor force production and resistance to fatigue compared to novices during bouts of climbing on a treadwall system. This may be attributed to physiological changes due to years of training, such as metabolic adaptations and oxygenation capacity in the forearm musculature.

scholarly journals Triceps surae torque-length relationships relevant for walking activity levels with and without an ankle exoskeleton

2019 ◽  
Author(s):  
Anthony L. Hessel ◽  
Brent J. Raiteri ◽  
Michael J. Marsh ◽  
Daniel Hahn
Keyword(s):  
Muscle Activity ◽  
Metabolic Cost ◽  
Activity Levels ◽  
Plantar Flexor ◽  
Plantar Flexors ◽  
Flexor Muscle ◽  
Fascicle Length ◽  
Lateral Gastrocnemius ◽  
Work Requirements ◽  
Ankle Exoskeleton

AbstractAnkle exoskeletons have been developed to assist walking by offloading the plantar flexors work requirements, which reduces muscle activity level. However, reduced muscle activity alters plantar flexor muscle-tendon unit dynamics in a way that is poorly understood. We therefore evaluated torque-fascicle length properties of the soleus and lateral gastrocnemius during voluntary contractions at simulated activity levels typical during late stance with and without an ankle exoskeleton. Soleus activity levels (100, 30, and 22% maximal voluntary activity) were produced by participants via visual electromyography feedback at ankle angles ranging from −10° plantar flexion to 35° dorsiflexion. Using dynamometry and ultrasound imaging, torque-fascicle length data of the soleus and lateral gastrocnemius were produced. The results indicate that muscle activity reductions observed with an exoskeleton shift the torque-angle and torque-fascicle length curves to more dorsiflexed ankle angles and longer fascicle lengths where no descending limb is physiologically possible. This shift is in line with previous simulations that predicted a similar increase in the operating fascicle range when wearing an exoskeleton. These data suggest that a small reduction in muscle activity causes changes to torque-fascicle length properties, which has implications for the design and testing of future ankle exoskeletons for assisted walking.Significance StatementAssistive lower-limb exoskeletons reduce the metabolic cost of walking by reducing the positive work requirements of the plantar flexor muscles. However, if the exoskeleton reduces plantar flexor muscle activity too much, then the metabolic benefit is lost. The biological reasons for this are unclear and hinder further exoskeleton development. This research study is the first to directly evaluate if a reduction in plantar flexor muscle activity similar to that caused by wearing an exoskeleton affects muscle function. We found that reduced muscle activity changes the torque-length properties of two plantar flexors, which could explain why reducing muscle activity too much can increase metabolic cost.

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