Combined effect of repetitive work and cold on muscle function and fatigue

2002 ◽  
Vol 92 (1) ◽  
pp. 354-361 ◽  
Author(s):  
Juha Oksa ◽  
Michel B. Ducharme ◽  
Hannu Rintamäki
Keyword(s):  
Muscle Function ◽  
Voluntary Contraction ◽  
Overuse Injuries ◽  
Emg Activity ◽  
Wrist Flexion ◽  
Fatigue Index ◽  
Local Cooling ◽  
Repetitive Work ◽  
Flexion Extension ◽  
Forearm Muscle

This study compared the effect of repetitive work in thermoneutral and cold conditions on forearm muscle electromyogram (EMG) and fatigue. We hypothesize that cold and repetitive work together cause higher EMG activity and fatigue than repetitive work only, thus creating a higher risk for overuse injuries. Eight men performed six 20-min work bouts at 25°C (W-25) and at 5°C while exposed to systemic (C-5) and local cooling (LC-5). The work was wrist flexion-extension exercise at 10% maximal voluntary contraction. The EMG activity of the forearm flexors and extensors was higher during C-5 (31 and 30%, respectively) and LC-5 (25 and 28%, respectively) than during W-25 ( P < 0.05). On the basis of fatigue index (calculated from changes in maximal flexor force and flexor EMG activity), the fatigue in the forearm flexors at the end of W-25 was 15%. The corresponding values at the end of C-5 and LC-5 were 37% ( P < 0.05 in relation to W-25) and 20%, respectively. Thus repetitive work in the cold causes higher EMG activity and fatigue than repetitive work in thermoneutral conditions.

Characterizing forearm muscle activity in young adults during dynamic wrist flexion–extension movement using a wrist robot

2020 ◽  
Vol 108 ◽  
pp. 109908
Author(s):  
Davis A. Forman ◽  
Garrick N. Forman ◽  
Edwin J. Avila-Mireles ◽  
Maddalena Mugnosso ◽  
Jacopo Zenzeri ◽  
...  
Keyword(s):  
Young Adults ◽  
Muscle Activity ◽  
Wrist Flexion ◽  
Flexion Extension ◽  
Forearm Muscle

Postmovement Changes in the Frequency and Amplitude of Physiological Tremor Despite Unchanged Neural Output

2010 ◽  
Vol 104 (4) ◽  
pp. 2020-2023 ◽  
Author(s):  
Raymond Reynolds ◽  
Martin Lakie
Keyword(s):  
Passive Movement ◽  
Muscle Stiffness ◽  
Emg Activity ◽  
Hand Position ◽  
Vertical Acceleration ◽  
Physiological Tremor ◽  
Joint Mechanics ◽  
Wrist Flexion ◽  
Temporary Reduction ◽  
Flexion Extension

Active or passive movement causes a temporary reduction in muscle stiffness that gradually returns to baseline levels when the muscle remains still. This effect, termed muscle thixotropy, alters the mechanical properties of the joint around which the muscle acts, reducing its resonant frequency. Because physiological tremor is affected by joint mechanics, this suggests that prior movement may alter tremor independently of neural output. To address this possibility, vertical acceleration of the outstretched prone hand was recorded in eight healthy subjects, along with EMG activity of the extensor digitorum communis muscle. A series of voluntary wrist flexion/extension movements was performed every 20 s, interspersed by periods during which hand position was maintained. Time-dependent changes in the amplitude and frequency of acceleration and EMG were analyzed using a continuous wavelet transform. Immediately following movement, acceleration displayed a significant increase in wavelet power accompanied by a reduction in peak frequency. During the postmovement period, power declined by 63%, and frequency increased from 7.2 to 8.0 Hz. These changes occurred with an exponential time constant of 2–4 s, consistent with a thixotropic mechanism. In contrast to acceleration, EMG activity showed no significant changes despite being strongly related to acceleration during the movement itself. These results show that prior movement transiently increases the amplitude and reduces the frequency of physiological tremor, despite unchanging neural output. This effect is best explained by a reduction in joint stiffness caused by muscle thixotropy, highlighting the importance of mechanical factors in the genesis of physiological tremor.

Effects of vibratory massage therapy on grip strength, endurance time and forearm muscle performance

Work ◽  
2021 ◽  
Vol 68 (3) ◽  
pp. 619-632
Author(s):  
Mohd Mukhtar Alam ◽  
Abid Ali Khan ◽  
Mohd Farooq
Keyword(s):  
Grip Strength ◽  
Pearson Correlation ◽  
Massage Therapy ◽  
Voluntary Contraction ◽  
Muscle Performance ◽  
Emg Activity ◽  
Endurance Time ◽  
Vibration Therapy ◽  
Forearm Muscle ◽  
Grip Endurance

BACKGROUND: Vibration therapy (VT) causes an increase in motor unit activation tendency, an involuntary recruitment of earlier sedentary motor units, which increases the muscle fiber force generating capacity and muscle performance. OBJECTIVE: To evaluate the effect of vibratory massage therapy at 23 Hz and 35 Hz on grip strength, endurance, and forearm muscle performance (in terms of EMG activity). METHODS: Ten healthy and right-handed men participated voluntarily in this study. The experiment was characterized by the measurement of MVC (maximal voluntary contraction) grip strength and grip endurance time at 50%MVC, accompanied by the corresponding measurement of the EMG signals of the muscles viz., flexor digitorum superficialis (FDS); flexor carpi ulnaris (FCU); extensor carpi radialis brevis (ECRB); and extensor carpi ulnaris (ECU) in supine posture. RESULTS: MANCOVA results showed significant effects of VT frequency on endurance time (p < 0.001); but no significant effect on the grip strength (p = 0.161) and muscle performance (in terms of EMG activities of the forearm muscles). However, VT improves the MVC grip strength and grip endurance time (better at 35 Hz). The Pearson correlation was significant between: weight, palm length, palm circumference, and forearm length with MVC grip strength; and the palm length with the endurance time. In addition, the palm length, palm circumference, and forearm circumference generally serve to better predict MVC grip strength and grip endurance time. CONCLUSIONS: Vibration therapy at 35 Hz for 10 minutes on the forearms had a significant positive effect on the neuromuscular performance to enhance muscle performance of upper extermitites and can be used as the optimal range to study the effect of VT. Findings may be used to prepare guidelines for VT in rehabilitation, healthcare, sports, and medical for therapists.

Microstimulation mapping of precentral cortex during trained movements

1990 ◽  
Vol 64 (6) ◽  
pp. 1668-1682 ◽  
Author(s):  
E. M. Schmidt ◽  
J. S. McIntosh
Keyword(s):  
Emg Activity ◽  
Cortical Region ◽  
Intracortical Microstimulation ◽  
Joint Movement ◽  
Wrist Flexion ◽  
Motoneuron Pool ◽  
Different Types ◽  
Muscle Inhibition ◽  
Forearm Muscle ◽  
Flexion And Extension

1. The precentral cortex of three Macaca mulatta monkeys were mapped with intracortical microstimulation (ICMS) while the monkeys performed alternating wrist flexion and extension movements. A forearm cocontraction task was also employed with one monkey. Electromyogram (EMG) recordings from forearm muscles were used to evaluate the results of ICMS. 2. We have found that the results of ICMS can be misleading if EMG activity is not recorded from the responding muscle. Inhibition can be interpreted as excitation if muscle palpation or joint movement are the only response criteria. 3. Movement of the stimulating electrode by as little as 200 microns in a single radial column sometimes changed EMG responses from inhibition to excitation or vice versa, indicating that cortical inhibitory areas for a muscle can be located very close to excitatory zones. 4. Both excitation and inhibition of muscles could be produced with ICMS of precentral cortex when the animal was performing a task involving the muscles being mapped. EMG responses to ICMS were stable, provided that the stimulation was applied at the same time during a repetitive task such that the motoneurons were at a given level of excitability. 5. Zones where ICMS produced inhibition of a particular forearm muscle were interspersed among zones that produced excitation for that muscle. 6. Regions exist in precentral cortex where ICMS activates antagonistic wrist muscles producing cocontraction. 7. The extensive cortical region from which any individual muscle can be activated or suppressed with ICMS and the various combinations of muscles that are activated from within this region suggest that different types of movements involving a single muscle are represented at different locations within this region. 8. At a few locations in precentral cortex, the EMG responses to ICMS were not just a function of the level of excitation of the motoneuron pool at the time of stimulation but were also dependent on the specific task the monkey was performing at the time of stimulation.

Upper Extremity Kinetics in Poultry Processing: A Comparison between Two Different Cutting Tasks

2003 ◽  
Vol 19 (2) ◽  
pp. 169-177 ◽  
Author(s):  
Dwight E. Waddell ◽  
Craig Wyvill ◽  
Robert J. Gregor
Keyword(s):  
Risk Factors ◽  
Upper Extremity ◽  
Assessment System ◽  
Emg Activity ◽  
Wrist Flexion ◽  
External Work ◽  
Factors Associated ◽  
Flexion Extension ◽  
Poultry Processing ◽  
Trauma Disorders

A field study was performed using a new data collection system looking at upper extremity kinetics during two different cutting tasks, wing vs. tender cuts, in three poultry plants. The Ergonomic Work Assessment System (EWAS) was designed to simultaneously record knife forces (Fx, Fy, and Fz), electromyographic (EMG) activity (forearm flexors/extensors), and goniometric data (wrist flexion/extension), all of which may represent risk factors associated with cumulative trauma disorders, specifically carpal tunnel syndrome (CTS). The objective of this study was to monitor workers in an unencumbered fashion as they performed two different poultry cutting tasks. It was assumed that the variables measured by EWAS would be able to discriminate between the two cuts and quantify possible differences between the two. The results confirmed that EWAS successfully showed significant differences in knife forces between the wing and tender cuts. Knife force differences were also observed between plants for the same cut. Differences in the two cuts were also identified in the EMG and wrist angles. EWAS successfully quantified variables that may represent risk factors associated with CTS in three poultry plants. Knowledge of a better quantitatively described external work environment may enable plants to better design rotation schedules for their deboners.

scholarly journals Design and Development of Continuous Passive Motion (CPM) for Fingers and Wrist Grounded-Exoskeleton Rehabilitation System

2021 ◽  
Vol 11 (2) ◽  
pp. 815
Author(s):  
Husam Almusawi ◽  
Géza Husi
Keyword(s):  
Experimental Testing ◽  
Hand Movement ◽  
Evaluation Process ◽  
Continuous Passive Motion ◽  
Wrist Flexion ◽  
Design And Development ◽  
Passive Motion ◽  
Assistive Robots ◽  
Flexion Extension ◽  
Design Characteristics

Impairments of fingers, wrist, and hand forearm result in significant hand movement deficiencies and daily task performance. Most of the existing rehabilitation assistive robots mainly focus on either the wrist training or fingers, and they are limiting the natural motion; many mechanical parts associated with the patient’s arms, heavy and expensive. This paper presented the design and development of a new, cost-efficient Finger and wrist rehabilitation mechatronics system (FWRMS) suitable for either hand right or left. The proposed machine aimed to present a solution to guide individuals with severe difficulties in their everyday routines for people suffering from a stroke or other motor diseases by actuating seven joints motions and providing them repeatable Continuous Passive Motion (CPM). FWRMS approach uses a combination of; grounded-exoskeleton structure to provide the desired displacement to the hand’s four fingers flexion/extension (F/E) driven by an indirect feed drive mechanism by adopting a leading screw and nut transmission; and an end-effector structure to provide angular velocity to the wrist flexion/ extension (F/E), wrist radial/ulnar deviation (R/U), and forearm supination/pronation (S/P) driven by a rotational motion mechanism. We employed a single dual-sided actuator to power both mechanisms. Additionally, this article presents the implementation of a portable embedded controller. Moreover, this paper addressed preliminary experimental testing and evaluation process. The conducted test results of the FWRMS robot achieved the required design characteristics and executed the motion needed for the continuous passive motion rehabilitation and provide stable trajectories guidance by following the natural range of motion (ROM) and a functional workspace of the targeted joints comfortably for all trainable movements by FWRMS.

Unraveling Interlimb Interactions Underlying Bimanual Coordination

2005 ◽  
Vol 94 (5) ◽  
pp. 3112-3125 ◽  
Author(s):  
Arne Ridderikhoff ◽  
C. (Lieke) E. Peper ◽  
Peter J. Beek
Keyword(s):  
Bimanual Coordination ◽  
Feedforward Control ◽  
Emg Activity ◽  
Minor Role ◽  
Error Corrections ◽  
Flexion Extension ◽  
Contralateral Hand ◽  
Phase Coordination ◽  
The Stability ◽  
Passive Movements

Three sources of interlimb interactions have been postulated to underlie the stability characteristics of bimanual coordination but have never been evaluated in conjunction: integrated timing of feedforward control signals, phase entrainment by contralateral afference, and timing corrections based on the perceived error of relative phase. In this study, the relative contributions of these interactions were discerned through systematic comparisons of five tasks involving rhythmic flexion–extension movements about the wrist, performed bimanually (in-phase and antiphase coordination) or unimanually with or without comparable passive movements of the contralateral hand. The main findings were the following. 1) Contralateral passive movements during unimanual active movements induced phase entrainment to interlimb phasing of either 0° (in-phase) or 180° (antiphase). 2) Entrainment strength increased with the passive movements' amplitude, but was similar for in-phase and antiphase movements. 3) Coordination of unimanual active movements with passive movements of the contralateral hand (kinesthetic tracking) was characterized by similar bilateral EMG activity as observed in active bimanual coordination. 4) During kinesthetic tracking the timing of the movements of the active hand was modulated by afference-based error corrections, which were more pronounced during in-phase coordination. 5) Indications of in-phase coordination being more stable than antiphase coordination were most prominent during active bimanual coordination and marginal during kinesthetic tracking. Together the results indicated that phase entrainment by contralateral afference contributed equally to the stability of in-phase and antiphase coordination, and that differential stability of these patterns depended predominantly on integrated timing of feedforward signals, with only a minor role for afference-based error corrections.

scholarly journals Isolated Core Training Improves Sprint Performance in National-Level Junior Swimmers

2015 ◽  
Vol 10 (2) ◽  
pp. 204-210 ◽  
Author(s):  
Matthew Weston ◽  
Angela E. Hibbs ◽  
Kevin G. Thompson ◽  
Iain R. Spears
Keyword(s):  
Beneficial Effect ◽  
National Level ◽  
Intervention Group ◽  
Voluntary Contraction ◽  
Emg Activity ◽  
Control Group ◽  
Front Crawl ◽  
Swim Performance ◽  
The Core ◽  
Core Training

Purpose:To quantify the effects of a 12-wk isolated core-training program on 50-m front-crawl swim time and measures of core musculature functionally relevant to swimming.Methods:Twenty national-level junior swimmers (10 male and 10 female, 16 ± 1 y, 171 ± 5 cm, 63 ± 4 kg) participated in the study. Group allocation (intervention [n = 10], control [n = 10]) was based on 2 preexisting swim-training groups who were part of the same swimming club but trained in different groups. The intervention group completed the core training, incorporating exercises targeting the lumbopelvic complex and upper region extending to the scapula, 3 times/wk for 12 wk. While the training was performed in addition to the normal pool-based swimming program, the control group maintained their usual pool-based swimming program. The authors made probabilistic magnitude-based inferences about the effect of the core training on 50-m swim time and functionally relevant measures of core function.Results:Compared with the control group, the core-training intervention group had a possibly large beneficial effect on 50-m swim time (–2.0%; 90% confidence interval –3.8 to –0.2%). Moreover, it showed small to moderate improvements on a timed prone-bridge test (9.0%; 2.1–16.4%) and asymmetric straight-arm pull-down test (23.1%; 13.7–33.4%), and there were moderate to large increases in peak EMG activity of core musculature during isolated tests of maximal voluntary contraction.Conclusion:This is the first study to demonstrate a clear beneficial effect of isolated core training on 50-m front-crawl swim performance.

scholarly journals Electrical Stimulation Frequency and Skeletal Muscle Characteristics: Effects on Force and Fatigue

2017 ◽  
Vol 27 (4) ◽  
Author(s):  
Maria Vromans ◽  
Pouran Faghri
Keyword(s):  
Electrical Stimulation ◽  
Vastus Lateralis ◽  
Voluntary Contraction ◽  
Current Intensity ◽  
Muscle Size ◽  
Emg Activity ◽  
Abductor Pollicis Brevis ◽  
Fiber Composition ◽  
Initial Drop ◽  
Initial Force

This investigation aimed to determine the force and muscle surface electromyography (EMG) responses to different frequencies of electrical stimulation (ES) in two groups of muscles with different size and fiber composition (fast- and slow-twitch fiber proportions) during a fatigue-inducing protocol. Progression towards fatigue was evaluated in the abductor pollicis brevis (APB) and vastus lateralis (VL) when activated by ES at three frequencies (10, 35, and 50Hz). Ten healthy adults (mean age: 23.2 ± 3.0 years) were recruited; participants signed an IRB approved consent form prior to participation. Protocols were developed to 1) identify initial ES current intensity required to generate the 25% maximal voluntary contraction (MVC) at each ES frequency and 2) evaluate changes in force and EMG activity during ES-induced contraction at each frequency while progressing towards fatigue. For both muscles, stimulation at 10Hz required higher current intensity of ES to generate the initial force. There was a significant decline in force in response to ES-induced fatigue for all frequencies and for both muscles (p<0.05). However, the EMG response was not consistent between muscles. During the progression towards fatigue, the APB displayed an initial drop in force followed by an increase in EMG activity and the VL displayed a decrease in EMG activity for all frequencies. Overall, it appeared that there were some significant interactions between muscle size and fiber composition during progression towards fatigue for different ES frequencies. It could be postulated that muscle characteristics (size and fiber composition) should be considered when evaluating progression towards fatigue as EMG and force responses are not consistent between muscles.

Quantification of Hand Grip Force under Dynamic Conditions

1993 ◽  
Vol 37 (10) ◽  
pp. 715-719 ◽  
Author(s):  
Katherine R. Lehman ◽  
W. Gary Allread ◽  
P. Lawrence Wright ◽  
William S. Marras
Keyword(s):  
Grip Force ◽  
Wrist Flexion ◽  
Range Of Movement ◽  
Ulnar Deviation ◽  
Dynamic Conditions ◽  
Radial Deviation ◽  
Hand Grip ◽  
Flexion Extension ◽  
Maximum Grip ◽  
Lower Grip

A laboratory experiment was conducted to determine whether grip force capabilities are lower when the wrist is moved than in a static position. The purpose was to determine the wrist velocity levels and wrist postures that had the most significant effect on grip force. Maximum grip forces of five male and five female subjects were determined under both static and dynamic conditions. The dominant wrist of each subject was secured to a CYBEX II dynamometer and grip force was collected during isokinetic wrist deviations for four directions of motion (flexion to extension, extension to flexion, radial to ulnar, and ulnar to radial). Six different velocity levels were analyzed and grip forces were recorded at specific wrist positions throughout each range of movement. For flexion-extension motions, wrist positions from 45 degrees flexion to 45 degrees extension were analyzed whereas positions from 20 degrees radial deviation to 20 degrees ulnar deviation were studied for radial-ulnar activity. Isometric exertions were also performed at each desired wrist position. Results showed that, for all directions of motion, grip forces for all isokinetic conditions were significantly lower than for the isometric exertions. Lower grip forces were exhibited at extreme wrist flexion and extreme radial and ulnar positions for both static and dynamic conditions. The direction of motion was also found to affect grip strength; extension to flexion exertions produced larger grip forces than flexion to extension exertions and radial to ulnar motion showed larger grip forces than ulnar to radial deviation. Although, males produced larger grip forces than females in all exertions, significant interactions between gender and velocity were noted.

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