Cutting Force and EMG Recordings for Ergonomics Assessment of Meat Cutting Tasks: Influence of the Workbench Height and the Cutting Direction on Muscle Activation Levels

2012 ◽  
Author(s):  
Charles Pontonnier ◽  
Georges Dumont ◽  
Mark de Zee ◽  
Afshin Samani ◽  
Pascal Madeleine
Keyword(s):  
Upper Extremity ◽  
Muscle Activation ◽  
Biceps Brachii ◽  
Control Strategies ◽  
Arm Movement ◽  
Design Parameters ◽  
Assessment Protocol ◽  
Upper Trapezius ◽  
Long Head ◽  
Cutting Direction

Repetitive arm movement and force exertion are common in meat cutting tasks and often lead to musculosketal disorders. In this study, the effects of the workbench height and the cutting direction on the levels of muscular activation of the upper extremity during meat cutting tasks were investigated. Seven subjects performed 4 trials of 20s each at the 4 different heights (0 cm, −10 cm, −20 cm and −30 cm below the elbow height), alternating two cutting directions. Activation levels of upper extremity muscles (biceps brachii, triceps long head, deltoideus anterior, deltoideus medialis and upper trapezius) and cutting forces were recorded synchronously. Then the trends of the normalized activations with regard to the workplace design parameters (table height and cutting direction) were computed. Results showed that the optimal configuration is a partially related to the task, whereas motor control strategies have also an influence on it. The present results provide new key information about the effects of workbench heights during a repetitive meat cutting task and a complete assessment protocol to analyse workstation design parameters influence on muscles activation levels.

scholarly journals Glenohumeral Muscle Activation During Provocative Tests Designed to Diagnose Superior Labrum Anterior-Posterior Lesions

2011 ◽  
Vol 39 (12) ◽  
pp. 2670-2678 ◽  
Author(s):  
Vanessa J.C. Wood ◽  
Michelle B. Sabick ◽  
Ron P. Pfeiffer ◽  
Seth M. Kuhlman ◽  
Jason H. Christensen ◽  
...  
Keyword(s):  
Muscle Activity ◽  
Muscle Activation ◽  
Biceps Brachii ◽  
External Rotation ◽  
Slap Lesion ◽  
Radiographic Findings ◽  
Superior Labrum ◽  
Long Head ◽  
Supination External Rotation ◽  
Anterior Posterior

Background: Despite considerable medical advances, arthroscopy remains the only definitive means of superior labrum anterior-posterior (SLAP) lesion diagnosis. Natural shoulder anatomic variants limit the reliability of radiographic findings and clinical evaluations are not consistent. Accurate clinical diagnostic techniques would be advantageous because of the invasiveness, patient risk, and financial cost associated with arthroscopy. Purpose: The purpose of this study was to examine the behavior of the joint-stabilizing muscles in provocative tests for SLAP lesions. Electromyography was used to characterize the muscle behavior, with particular interest in the long head of the biceps brachii (LHBB), as activation of the long head and subsequent tension in the biceps tendon should, based on related research, elicit labral symptoms in SLAP lesion patients. Study Design: Controlled laboratory study. Methods: Volunteers (N = 21) without a history of shoulder injury were recruited. The tests analyzed were active compression, Speed’s, pronated load, biceps load I, biceps load II, resisted supination external rotation, and Yergason’s. Tests were performed with a dynamometer to improve reproducibility. Muscle activity was recorded for the long and short heads of the biceps brachii, anterior deltoid, pectoralis major, latissimus dorsi, infraspinatus, and supraspinatus. Muscle behavior for each test was characterized by peak activation and proportion of muscle activity. Results: Speed’s, active compression palm-up, bicep I, and bicep II produced higher long head activations. Resisted supination external rotation, bicep I, bicep II, and Yergason’s produced a higher LHBB proportion. Conclusion: Biceps load I and biceps load II elicited promising long head behavior (high activation and selectivity). Speed’s and active compression palm up elicited higher activation of the LHBB, and resisted supination and Yergason’s elicited selective LHBB activity. These top performing tests utilize a unique range of test variables that may prove valuable for optimal SLAP test design and performance. Clinical Relevance: This study examines several provocative tests that are frequently used in the clinical setting as a means of evaluating a potential SLAP lesion.

Shoulder Muscle Activation Levels During the Push-Up-Plus Exercise on Stable and Unstable Surfaces

2017 ◽  
Vol 26 (4) ◽  
pp. 281-286 ◽  
Author(s):  
Rafaela J.B. Torres ◽  
André L.T. Pirauá ◽  
Vinícius Y.S. Nascimento ◽  
Priscila S. dos Santos ◽  
Natália B. Beltrão ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Biceps Brachii ◽  
Emg Activity ◽  
Activity Levels ◽  
Triceps Brachii ◽  
Serratus Anterior ◽  
Upper Trapezius ◽  
Unstable Surface ◽  
Hands And Feet ◽  
Push Up

The aim of this study was to evaluate the acute effect of the use of stable and unstable surfaces on electromyography (EMG) activity and coactivation of the scapular and upper-limb muscles during the push-up plus (with full protraction of the scapula). Muscle activation of anterior deltoid (AD), posterior deltoid (PD), pectoralis major, biceps brachii (BB), triceps brachii (TB), upper trapezius (UT), middle trapezius (MT), lower trapezius (LT), and serratus anterior (SA) levels and coactivation index were determined by surface EMG in 20 young men during push-up plus performed on a stable and unstable condition (2 unstable devices applied to hands and feet). The paired t test and Cohen d were used for statistical analysis. The results showed that during the execution of the push-up plus on the unstable surface an increased EMG activity of the scapular stabilizing muscles (SA, MT, and LT) was observed, while AD and PD muscles showed a decrease. During exercise execution on the unstable surface there was a higher index of coactivation of the scapular muscles (SA–MT and UT–LT pairs). No significant differences were observed in TB–BB and AD–PD pairs. These results suggest that the push-up-plus exercise associated with unstable surfaces produced greater EMG activity levels and coactivation index of the scapular stabilizing muscle. On the other hand, the use of an unstable surface does not promote the same effect for the shoulder muscles.

scholarly journals Upper extremity biomechanics in native and non-native signers

Work ◽  
2021 ◽  
pp. 1-9
Author(s):  
Gretchen Roman ◽  
Daniel S. Peterson ◽  
Edward Ofori ◽  
Meghan E. Vidt
Keyword(s):  
Upper Extremity ◽  
Injury Risk ◽  
Muscle Activation ◽  
Joint Angle ◽  
Wrist Flexion ◽  
Upper Trapezius ◽  
Flexion Extension ◽  
Deaf Parents ◽  
Native Signers ◽  
Anterior Posterior

BACKGROUND: Individuals fluent in sign language (signers) born to non-signing, non-deaf parents (non-natives) may have a greater injury risk than signers born to signing, deaf parents (natives). A comprehensive analysis of movement while signing in natives and non-natives has not been completed and could provide insight into the greater injury prevalence of non-natives. OBJECTIVE: The objective of this study was to determine differences in upper extremity biomechanics between non-natives and natives. METHODS: Strength, ‘micro’ rests, muscle activation, ballistic signing, joint angle, and work envelope were captured across groups. RESULTS: Non-natives had fewer rests (p = 0.002) and greater activation (p = 0.008) in non-dominant upper trapezius. For ballistic signing, natives had greater anterior-posterior jerk (p = 0.033) and for joint angle, natives demonstrated greater wrist flexion-extension range of motion (p = 0.040). Natives also demonstrated greater maximum medial-lateral (p = 0.015), and greater minimum medial-lateral (p = 0.019) and superior-inferior (p = 0.027) positions. CONCLUSIONS: We observed that natives presented with more rests and less activation, but greater ballistic tendencies, joint angle, and envelope compared to non-natives. Additional work should explore potential links between these outcomes and injury risk in signers.

Muscle activation and biceps brachii strength under manual fixation of the scapula and different loading conditions

2020 ◽  
pp. 1-7
Author(s):  
Sungjoon Yun ◽  
Yongwook Kim
Keyword(s):  
Muscle Activation ◽  
Biceps Brachii ◽  
Elbow Flexion ◽  
Emg Activity ◽  
Loading Conditions ◽  
Serratus Anterior ◽  
Upper Trapezius ◽  
Exercise Condition ◽  
Increased Strength ◽  
Flexion Force

BACKGROUND: Few studies have reported the contribution of isometric-specific exercise of the biceps brachii muscle to increased strength under manual fixation of the scapula. OBJECTIVE: To investigate the activation amplitude of the biceps brachii (BB), serratus anterior (SA), and upper trapezius (UT) in a supine lying posture based on various exercise conditions. METHODS: The EMG activity of BB, SA, and UT was measured in 25 healthy adults while performing maximal elbow flexion exercise with or without manual stabilization of the scapula in two different loading conditions. RESULTS: Muscle activation of the BB was significantly greater when performed with manual fixation of the scapula under the wrist-loading exercise condition (p< 0.05) but manual fixation of the scapula or absence thereof did not have an effect. Elbow flexion force was significantly increased when applying manual fixation to the scapula in both the hand and wrist-loading exercise conditions (p< 0.05). There were no interaction effects between exercise conditions and manual fixation (with or without) in any of the EMG activation values (p> 0.05). CONCLUSION: Manual stabilization of the scapula is a useful therapeutic technique to increase BB strength. Such an intervention may also be indicated for accurate strength measurement of this muscle.

Shoulder Muscle Activation Levels During Exercises With Axial and Rotational Load on Stable and Unstable Surfaces

2017 ◽  
Vol 33 (2) ◽  
pp. 118-123 ◽  
Author(s):  
Vinícius Yan Santos Nascimento ◽  
Rafaela Joyce Barbosa Torres ◽  
Natália Barros Beltrão ◽  
Priscila Soares dos Santos ◽  
André Luiz Torres Pirauá ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Bench Press ◽  
Biceps Brachii ◽  
Emg Activity ◽  
Triceps Brachii ◽  
Serratus Anterior ◽  
Upper Trapezius ◽  
Unstable Surface ◽  
Lower Trapezius ◽  
Rotational Load

This study evaluated the effects of instability on the EMG activity of scapular stabilizing and upper limb muscles during exercises with axial and rotational load. Twenty male volunteers (20.9 ± 1.8 years, 174.1 ± 0.04 cm, 73.17 ± 8.77 kg) experienced in strength training participated in a crossover design. Muscle activation of anterior deltoid (AD), posterior deltoid (PD), pectoralis major (PM), biceps brachii (BB), triceps brachii (TB), upper trapezius (UT), middle trapezius (MT), lower trapezius (LT), and serratus anterior (SA) were determined on both conditions. Participants performed a single series of 10 repetitions of bench press and fly exercises on stable (bench) and unstable (proprioceptive disc) conditions at 60% of 1-RM. The Friedman test and post hoc Dunn’s indicated that the unstable condition showed greater EMG activity for AD (P = .001) and BB (P = .002) on the fly exercise, SA (P = .001) and LT (P = .048) on the bench press, and PM (P ≤ .002) on both exercises. These results show that using an unstable surface in exercises with rotational load provides superior EMG activity of the agonist muscles, while in exercise with axial load, the instability favors EMG activity of the scapular stabilizing muscles.

scholarly journals The comparison of the shoulder muscle activation in patients with rotator cuff tear under an abduction brace among the three postures

2021 ◽  
pp. 14
Author(s):  
Keyword(s):  
Rotator Cuff ◽  
Rotator Cuff Tear ◽  
Supine Position ◽  
Repeated Measures ◽  
Muscle Activation ◽  
Biceps Brachii ◽  
Sitting Position ◽  
Cuff Tear ◽  
Upper Trapezius ◽  
Anterior Deltoid

Background: Immobilization using an abduction brace is essential for the relaxation of the rotator cuff and scapular muscles and the prevention of a retear in patients with rotator cuff tear after arthroscopic rotator cuff repair (ARCR). However, thus far, the comparison of the scapular muscle activities has not been compared among different postures under an abduction brace in patients after ARCR. Objectives: The purpose of our study was to compare the scapular muscle activities among the supine position, sitting position, and walking under an abduction brace before and after ARCR Study Design: Observational, repeated measures study. Methods: Twelve patients with full-thickness rotator cuff tears were studied. The mean patient age was 64.7 years. The scapular muscle activations of the ipsilateral limbs were measured using surface electromyography in three postures: supine position, sitting position, and walking. The integrated electromyography relative values of the upper trapezius, anterior deltoid, middle deltoid, and biceps brachii were compared preoperatively and at two weeks after ARCR. Results: The trapezius, biceps brachii, and middle deltoid in the walking showed significantly higher integrated electromyography relative values than those in the supine position, preoperatively and at two weeks after surgery. The anterior deltoid in the sitting position had significantly higher integrated electromyography relative values than those in the supine position. Conclusions: Postures affected the scapular muscle activities in ARCR patients under an abduction brace. Understanding the influence of posture on the scapular muscle activity after ARCR will help rehabilitation accurately and appropriately.

scholarly journals Investigating the Effects of Mental Fatigue on Resistance Exercise Performance

2021 ◽  
Vol 18 (13) ◽  
pp. 6794
Author(s):  
Denver M. Y. Brown ◽  
Amanda Farias Zuniga ◽  
Daanish M. Mulla ◽  
Divya Mendonca ◽  
Peter J. Keir ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Perceived Exertion ◽  
Biceps Brachii ◽  
Experimental Manipulation ◽  
Mental Fatigue ◽  
Erector Spinae ◽  
Future Research ◽  
Dynamic Resistance ◽  
Triceps Brachii ◽  
Upper Trapezius

Mental fatigue can impart negative effects on subsequent physical performance, although the mechanisms underlying these effects are not well understood. This study examined whether mental fatigue confers negative carryover effects on the performance of a set of biceps curls, while also investigating physiological and psychological mechanisms proposed to explain the predicted effect. A randomized, cross-over design was employed. On visit 1, participants (N = 10) performed a barbell biceps curl one-repetition maximum (1RM) test. On visits 2–3, participants performed 20 biceps curls at 50% of their 1RM, followed by their respective 10 min experimental manipulation (high vs. low cognitive exertion) and then a second set of biceps curls to exhaustion. Ratings of perceived exertion and electromyography of the biceps brachii, triceps brachii, upper trapezius, thoracic erector spinae and lumbar erector spinae were recorded during the physical task. The total number of repetitions completed was similar across the conditions. Results also failed to show between-condition differences for muscle activation and perceptions of exertion. Future research is needed to build an adequate knowledge base to determine whether there is an effect of mental fatigue on dynamic resistance-based task performance and, if so, identify the mechanisms explaining how and why.

Sensitivity of muscle proton spin-spin relaxation time as an index of muscle activation

1994 ◽  
Vol 77 (1) ◽  
pp. 84-92 ◽  
Author(s):  
G. Yue ◽  
A. L. Alexander ◽  
D. H. Laidlaw ◽  
A. F. Gmitro ◽  
E. C. Unger ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Spin Relaxation ◽  
Muscle Activation ◽  
Biceps Brachii ◽  
Proton Spin ◽  
Spin Relaxation Time ◽  
Elbow Flexor ◽  
Flexor Muscles ◽  
Elbow Flexor Muscles ◽  
Long Head

The purpose of this study was to determine the minimum number of contractions that are needed to detect an increase in the muscle proton spin-spin relaxation time (T2) at a given exercise intensity. Five healthy human subjects performed five sets of an exercise that included concentric and eccentric contractions of the elbow-flexor muscles with loads that were 25 or 80% of maximum. With the 80% load, the five sets involved 1, 2, 5, 10, or 20 repetitions of the exercise; with the 25% load the five sets were 2, 5, 10, 20, or 40 repetitions. The upper arm of each subject was imaged before and immediately after each set of the exercise. Spin-echo images (repetition time/echo time = 2,000 ms/30, 60, 90, and 120 ms) were collected using an extremity coil, and T2 values were calculated. The signal intensity was measured from the elbow-flexor and -extensor muscles and from the bone marrow of the humerus. With the 80% load, T2 increased in the short head of the biceps brachii after two repetitions of the elbow exercise and after five repetitions in the brachialis and the long head of the biceps brachii. With the 25% load, T2 became longer after five repetitions of the exercise for the short head of the biceps brachii and after 10 repetitions for the brachialis and the long head of the biceps brachii. T2 varied linearly with the number of contraction repetitions for each of the elbow-flexor muscles at either load (r2 > or = 0.97, P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Swimming Practice and Scapular Kinematics, Scapulothoracic Muscle Activity, and the Pressure-Pain Threshold in Young Swimmers

2018 ◽  
Vol 53 (11) ◽  
pp. 1056-1062
Author(s):  
Fernanda A. P. Habechian ◽  
Ana Letícia Lozana ◽  
Ann M. Cools ◽  
Paula R. Camargo
Keyword(s):  
Upper Extremity ◽  
Analysis Of Variance ◽  
Muscle Activity ◽  
Pain Sensitivity ◽  
Muscle Activation ◽  
Pain Threshold ◽  
Pressure Pain Threshold ◽  
Scapular Kinematics ◽  
Upper Trapezius ◽  
Competitive Swimmers

Context Whereas alterations in scapular kinematics, scapulothoracic muscle activity, and pain sensitivity have been described in adult swimmers, no researchers have examined these outcomes in young swimmers. Objectives To compare scapular kinematics, scapulothoracic muscle activation, and the pressure-pain threshold (PPT) of the shoulder muscles among young nonpractitioners (those who were not involved in sports involving the upper limbs), amateur swimmers, and competitive swimmers. Design Cross-sectional study. Setting Laboratory. Patients or Other Participants A total of 90 individuals (age = 11.63 ± 0.61 years) in 3 groups: nonpractitioners, amateur swimmers, and competitive swimmers. Intervention(s) Scapular kinematics and activity of the upper trapezius, lower trapezius, and serratus anterior (SA) were measured during upper extremity elevation in the scapular plane. The PPT was assessed in the upper trapezius, infraspinatus, supraspinatus, middle deltoid, and tibialis anterior. Main Outcome Measure(s) Scapular kinematics, scapulothoracic muscle activation, and PPT. We conducted a 2-way mixed-model analysis of variance and a 1-way analysis of variance for scapular rotation and PPT, respectively. A Kruskal-Wallis test was used to assess muscle activity. The α level was set at .05. Results Competitive swimmers presented more internal rotation at 90° (P = .03) and 120° (P = .047) and more anterior tilt at 90° (P = .03) than nonpractitioners. Amateur swimmers demonstrated more anterior tilt at 90° (P = .004) and 120° (P = .005) than nonpractitioners. Competitive swimmers had greater SA activation in the intervals from 60° to 90° (P = .02) and 90° to 120° (P = .01) than amateur swimmers. They also displayed more SA activation in the interval from 90° to 120° than nonpractitioners (P = .04). No differences were found in any of the muscles for the PPT (P &gt; .05). Conclusions Young competitive swimmers presented alterations in scapular kinematics and scapulothoracic muscle activation during upper extremity elevation that may be due to sport practice. Mechanical pain sensitivity was not altered in young swimmers.

scholarly journals Investigating the effects of mental fatigue on resistance exercise performance

2021 ◽  
Author(s):  
Denver M. Y. Brown ◽  
Amanda Farias Zuniga ◽  
Daanish Mulla ◽  
Divya Mendonca ◽  
Peter Keir ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Perceived Exertion ◽  
Biceps Brachii ◽  
Experimental Manipulation ◽  
Mental Fatigue ◽  
Erector Spinae ◽  
Future Research ◽  
Dynamic Resistance ◽  
Triceps Brachii ◽  
Upper Trapezius

Mental fatigue can impart negative effects on subsequent physical performance, although the mechanisms underlying these effects are not well understood. This study examined whether mental fatigue confers negative carryover effects on the performance of a set of biceps curls, while also investigating physiological and psychological mechanisms proposed to explain the predicted effect. A randomized, cross-over design was employed. On Visit 1, participants (N = 10) performed a barbell biceps curl one-repetition maximum (1RM) test. On Visits 2/3, participants performed 20 biceps curls at 50% of their 1RM, followed by their respective 10-minute experimental manipulation (high vs. low cognitive exertion), and then a second set of biceps curls to exhaustion. Ratings of perceived exertion and electromyography of the biceps brachii, triceps brachii, upper trapezius, thoracic erector spinae, and lumbar erector spinae were recorded during the physical task. The total number of repetitions completed was similar across the conditions. Results also failed to show between-condition differences for muscle activation and perceptions of exertion. Future research is needed to build an adequate knowledge base to determine whether there is an effect of mental fatigue on dynamic resistance-based task performance, and if so, identifying the mechanisms explaining how and why.

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