scholarly journals Scapular Muscle-Activation Ratios in Patients With Shoulder Injuries During Functional Shoulder Exercises

2014 ◽  
Vol 49 (3) ◽  
pp. 345-355 ◽  
Author(s):  
Chad R. Moeller ◽  
Kellie C. Huxel Bliven ◽  
Alison R. Snyder Valier
Keyword(s):  
Muscle Activity ◽  
Muscle Activation ◽  
External Rotation ◽  
Whole Body ◽  
Shoulder Injuries ◽  
Individual Muscle ◽  
Study Results ◽  
Bow And Arrow ◽  
Healthy Control ◽  
Injured Athletes

Context: Alterations in scapular muscle activation, which are common with glenohumeral (GH) injuries, affect stability and function. Rehabilitation aims to reestablish activation between muscles for stability by progressing to whole-body movements. Objective: To determine scapular muscle-activation ratios and individual muscle activity (upper trapezius [UT], middle trapezius [MT], lower trapezius [LT], serratus anterior [SA]) differences between participants with GH injuries and healthy control participants during functional rehabilitation exercises. Design: Cross-sectional study. Setting: Laboratory. Patients or Other Participants: Thirty-nine participants who had GH injuries (n = 20; age = 23.6 ± 3.2 years, height = 170.7 ± 11.5 cm, mass = 74.7 ± 13.1 kg) or were healthy (n = 19; age = 24.4 ± 3.3 years, height = 173.6 ± 8.6 cm, mass = 74.7 ± 14.8 kg) were tested. Intervention(s): Clinical examination confirmed each participant's classification as GH injury or healthy control. Participants performed 4 exercises (bow and arrow, external rotation with scapular squeeze, lawnmower, robbery) over 3 seconds with no load while muscle activity was recorded. Main Outcome Measure(s): We used surface electromyography to measure UT, MT, LT, and SA muscle activity. Scapular muscle-activation ratios (UT:MT, UT:LT, and UT:SA) were calculated (normalized mean electromyography of the UT divided by normalized mean electromyography of the MT, LT, and SA). Exercise × group analyses of variance with repeated measures were conducted. Results: No group differences for activation ratios or individual muscle activation amplitude were found (P > .05). Similar UT:MT and UT:LT activation ratios during bow-and-arrow and robbery exercises were seen (P > .05); both had greater activation than external-rotation-with-scapular-squeeze and lawnmower exercises (P < .05). The bow-and-arrow exercise elicited the highest activation from the UT, MT, and LT muscles; SA activation was greatest during the external-rotation-with-scapular-squeeze exercise. Conclusions: Scapular muscle activation was similar between participants with GH injuries and healthy control participants when performing the unloaded multiplanar, multijoint exercises tested. High activation ratios during the bow-and-arrow exercise indicate UT hyperactivity or decreased MT, LT, and SA activity. Our GH injury group may be comparable to high-functioning injured athletes. Study results may assist clinicians in selecting appropriate exercises for scapular muscle activation when caring for injured athletes.

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.

Individual Muscle Control Using an Exoskeleton Robot for Muscle Function Testing

2009 ◽  
Author(s):  
Jun Ueda ◽  
Moiz Hyderabadwala ◽  
Ming Ding ◽  
Tsukasa Ogasawara ◽  
Vijaya Krishnamoorthy ◽  
...  
Keyword(s):  
Muscle Activity ◽  
Muscle Function ◽  
Muscle Activation ◽  
Muscle Control ◽  
Wearable Robot ◽  
Activity Data ◽  
Individual Muscle ◽  
Exoskeleton Robot ◽  
Function Tests ◽  
Function Testing

A functionality test at the level of individual muscles by investigating the activity of a muscle of interest on various tasks may enable muscle-level force grading. This paper proposes a new method for muscle function tests using an exoskeleton robot for obtaining a wider variety of muscle activity data than standard motor tasks, e.g., pushing a handle by his/her hand. A computational algorithm systematically computes control commands to a wearable robot with actuators (an exoskeleton robot, or a power-assisting device) so that a desired muscle activation pattern for target muscle forces is induced. This individual muscle control method enables users (e.g., therapists) to efficiently conduct neuromuscular function tests for target muscles by arbitrarily inducing muscle activation patterns. Simulation results justify the use of an exoskeleton robot for muscle function testing in terms of the variety of muscle activity data.

scholarly journals Shoulder External Rotation Fatigue and Scapular Muscle Activation and Kinematics in Overhead Athletes

2011 ◽  
Vol 46 (4) ◽  
pp. 349-357 ◽  
Author(s):  
Mithun Joshi ◽  
Charles A. Thigpen ◽  
Kevin Bunn ◽  
Spero G. Karas ◽  
Darin A. Padua
Keyword(s):  
Muscle Fatigue ◽  
Muscle Activation ◽  
External Rotation ◽  
Shoulder Injuries ◽  
Serratus Anterior ◽  
Overhead Athletes ◽  
Scapular Kinematics ◽  
Fatigue Protocol ◽  
Upper Trapezius ◽  
Lower Trapezius

Context: Glenohumeral external rotation (GH ER) muscle fatigue might contribute to shoulder injuries in overhead athletes. Few researchers have examined the effect of such fatigue on scapular kinematics and muscle activation during a functional movement pattern. Objective: To examine the effects of GH ER muscle fatigue on upper trapezius, lower trapezius, serratus anterior, and infraspinatus muscle activation and to examine scapular kinematics during a diagonal movement task in overhead athletes. Setting: Human performance research laboratory. Design: Descriptive laboratory study. Patients or Other Participants: Our study included 25 overhead athletes (15 men, 10 women; age = 20 ± 2 years, height = 180 ± 11 cm, mass = 80 ± 11 kg) without a history of shoulder pain on the dominant side. Intervention(s): We tested the healthy, dominant shoulder through a diagonal movement task before and after a fatiguing exercise involving low-resistance, high-repetition, prone GH ER from 0° to 75° with the shoulder in 90° of abduction. Main Outcome Measure(s): Surface electromyography was used to measure muscle activity for the upper trapezius, lower trapezius, serratus anterior, and infraspinatus. An electromyographic motion analysis system was used to assess 3-dimensional scapular kinematics. Repeated-measures analyses of variance (phase × condition) were used to test for differences. Results: We found a decrease in ascending-phase and descending-phase lower trapezius activity (F1,25 = 5.098, P = .03) and an increase in descending-phase infraspinatus activity (F1,25 = 5.534, P = .03) after the fatigue protocol. We also found an increase in scapular upward rotation (F1,24 = 3.7, P = .04) postfatigue. Conclusions: The GH ER muscle fatigue protocol used in this study caused decreased lower trapezius and increased infraspinatus activation concurrent with increased scapular upward rotation range of motion during the functional task. This highlights the interdependence of scapular and glenohumeral force couples. Fatigue-induced alterations in the lower trapezius might predispose the infraspinatus to injury through chronically increased activation.

Torso and Hip Muscle Activity and Resulting Spine Load and Stability while Using the ProFitter 3-D Cross Trainer

2009 ◽  
Vol 25 (1) ◽  
pp. 73-84 ◽  
Author(s):  
Priyanka Banerjee ◽  
Stephen H.M Brown ◽  
Samuel J. Howarth ◽  
Stuart M. McGill
Keyword(s):  
Muscle Activity ◽  
Muscle Activation ◽  
Clinical Decision Making ◽  
Dynamic Balance ◽  
Gluteus Medius ◽  
Clinical Decision ◽  
Whole Body ◽  
Motor Patterns ◽  
Hip Muscle ◽  
Spine Mechanics

The ProFitter 3-D Cross Trainer is a labile surface device used in the clinic and claimed to train spine stability. The purpose of this study was to quantify the spine mechanics (compression and shear forces and stability), together with muscle activation mechanics (surface electromyography) of the torso and hip, during three ProFitter exercises. Trunk muscle activity was relatively low while exercising on the device (<25%MVC). Gluteus medius activity was phasic with the horizontal sliding position, especially for an experienced participant. Sufficient spinal stability was achieved in all three exercise conditions. Peak spinal compression values were below 3400 N (maximum 3188 N) and peak shear values were correspondingly low (under 500 N). The exercises challenge whole-body dynamic balance while producing very conservative spine loads. The motion simultaneously integrates hip and torso muscles in a way that appears to ensure stabilizing motor patterns in the spine. This information will assist with clinical decision making about the utility of the device and exercise technique in rehabilitation and training programs.

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.

scholarly journals Cortical control of locomotor muscle activity through muscle synergies in humans: a neural decoding study

2018 ◽  
Author(s):  
Hikaru Yokoyama ◽  
Naotsugu Kaneko ◽  
Tetsuya Ogawa ◽  
Noritaka Kawashima ◽  
Katsumi Watanabe ◽  
...  
Keyword(s):  
Muscle Activity ◽  
Muscle Activation ◽  
Indirect Evidence ◽  
Muscle Synergy ◽  
Muscle Synergies ◽  
Neural Decoding ◽  
Individual Muscle ◽  
Cortical Involvement ◽  
Decoding Accuracy

AbstractWalking movements are orchestrated by the activation of a large number of muscles. The control of numerous muscles during walking is believed to be simplified by flexible activation of groups of muscles called muscle synergies. Although significant corticomuscular connectivity during walking has been reported, the level at which the cortex controls locomotor muscle activity (i.e., muscle synergy or individual muscle level) remains unclear. Here, we examined cortical involvement in muscle control during walking by brain decoding of the activation of muscle synergies and individual muscles from electroencephalographic (EEG) signals using linear decoder models. First, we demonstrated that activation of locomotor muscle synergies was decoded from slow cortical waves with significant accuracy. In addition, we found that decoding accuracy for muscle synergy activation was greater than that for individual muscle activation and that decoding of individual muscle activation was based on muscle synergy-related cortical information. Taken together, these results provide indirect evidence that the cerebral cortex hierarchically controls multiple muscles through a few muscle synergies during walking. Our findings extend the current understanding of the role of the cortex in muscular control during walking and could accelerate the development of effective brain-machine interfaces for people with locomotor disabilities.

Characterization of the Frequency and Muscle Responses of the Lumbar and Thoracic Spines of Seated Volunteers During Sinusoidal Whole Body Vibration

2014 ◽  
Vol 136 (10) ◽  
Author(s):  
Hassam A. Baig ◽  
Daniel B. Dorman ◽  
Ben A. Bulka ◽  
Bethany L. Shivers ◽  
Valeta C. Chancey ◽  
...  
Keyword(s):  
Back Pain ◽  
Muscle Activity ◽  
Muscle Activation ◽  
Whole Body Vibration ◽  
Whole Body ◽  
Vibration Exposure ◽  
Body Vibration ◽  
Male Volunteers ◽  
Seat Vibration ◽  
Muscle Responses

Whole body vibration has been postulated to contribute to the onset of back pain. However, little is known about the relationship between vibration exposure, the biomechanical response, and the physiological responses of the seated human. The aim of this study was to measure the frequency and corresponding muscle responses of seated male volunteers during whole body vibration exposures along the vertical and anteroposterior directions to define the transmissibility and associated muscle activation responses for relevant whole body vibration exposures. Seated human male volunteers underwent separate whole body vibration exposures in the vertical (Z-direction) and anteroposterior (X-direction) directions using sinusoidal sweeps ranging from 2 to 18 Hz, with a constant amplitude of 0.4 g. For each vibration exposure, the accelerations and displacements of the seat and lumbar and thoracic spines were recorded. In addition, muscle activity in the lumbar and thoracic spines was recorded using electromyography (EMG) and surface electrodes in the lumbar and thoracic region. Transmissibility was determined, and peak transmissibility, displacement, and muscle activity were compared in each of the lumbar and thoracic regions. The peak transmissibility for vertical vibrations occurred at 4 Hz for both the lumbar (1.55 ± 0.34) and thoracic (1.49 ± 0.21) regions. For X-directed seat vibrations, the transmissibility ratio in both spinal regions was highest at 2 Hz but never exceeded a value of 1. The peak muscle response in both spinal regions occurred at frequencies corresponding to the peak transmissibility, regardless of the direction of imposed seat vibration: 4 Hz for the Z-direction and 2–3 Hz for the X-direction. In both vibration directions, spinal displacements occurred primarily in the direction of seat vibration, with little off-axis motion. The occurrence of peak muscle responses at frequencies of peak transmissibility suggests that such frequencies may induce greater muscle activity, leading to muscle fatigue, which could be a contributing mechanism of back pain.

Lower Limb Joint Angular Position and Muscle Activity During Elliptical Exercise in Healthy Young Men

2015 ◽  
Vol 31 (1) ◽  
pp. 19-27 ◽  
Author(s):  
Max R. Paquette ◽  
Audrey Zucker-Levin ◽  
Paul DeVita ◽  
Joseph Hoekstra ◽  
David Pearsall
Keyword(s):  
Lower Extremity ◽  
Muscle Activity ◽  
Muscle Activation ◽  
External Rotation ◽  
Angular Position ◽  
Frontal Plane ◽  
Contact Forces ◽  
Step Motion ◽  
Peak Knee ◽  
Gluteus Muscle

The purpose of this study was to compare lower extremity joint angular position and muscle activity during elliptical exercise using different foot positions and also during exercise on a lateral elliptical trainer. Sixteen men exercised on a lateral elliptical and on a standard elliptical trainer using straight foot position, increased toe-out angle, and a wide step. Motion capture and electromyography systems were used to obtain 3D lower extremity joint kinematics and muscle activity, respectively. The lateral trainer produced greater sagittal and frontal plane knee range of motion (ROM), greater peak knee flexion and extension, and higher vastus medialis activation compared with other conditions (P < .05). Toe-out and wide step produced the greatest and smallest peak knee adduction angles, respectively (P < .05). The lateral trainer produced greater sagittal and frontal plane hip ROM and greater peak hip extension and flexion compared with all other conditions (P < .05). Toe-out angle produced the largest peak hip external rotation angle and lowest gluteus muscle activation (P < .05). Findings from this study indicate that standard elliptical exercise with wide step may place the knee joint in a desirable frontal plane angular position to reduce medial knee loads, and that lateral elliptical exercise could help improve quadriceps strength but could also lead to larger knee contact forces.

scholarly journals Skeletal muscle power and fatigue at the tolerable limit of ramp-incremental exercise in COPD

2016 ◽  
Vol 121 (6) ◽  
pp. 1365-1373 ◽  
Author(s):  
Daniel T. Cannon ◽  
Ana Claudia Coelho ◽  
Robert Cao ◽  
Andrew Cheng ◽  
Janos Porszasz ◽  
...  
Keyword(s):  
Muscle Fatigue ◽  
Muscle Activity ◽  
Muscle Activation ◽  
Muscle Power ◽  
Incremental Exercise ◽  
Exercise Intolerance ◽  
Whole Body ◽  
Peak Exercise ◽  
Median Frequency ◽  
Copd Patients

Muscle fatigue (a reduced power for a given activation) is common following exercise in chronic obstructive pulmonary disease (COPD). Whether muscle fatigue, and reduced maximal voluntary locomotor power, are sufficient to limit whole body exercise in COPD is unknown. We hypothesized in COPD: 1) exercise is terminated with a locomotor muscle power reserve; 2) reduction in maximal locomotor power is related to ventilatory limitation; and 3) muscle fatigue at intolerance is less than age-matched controls. We used a rapid switch from hyperbolic to isokinetic cycling to measure the decline in peak isokinetic power at the limit of incremental exercise (“performance fatigue”) in 13 COPD patients (FEV1 49 ± 17%pred) and 12 controls. By establishing the baseline relationship between muscle activity and isokinetic power, we apportioned performance fatigue into the reduction in muscle activation and muscle fatigue. Peak isokinetic power at intolerance was ~130% of peak incremental power in controls (274 ± 73 vs. 212 ± 84 W, P < 0.05), but ~260% in COPD patients (187 ± 141 vs. 72 ± 34 W, P < 0.05), greater than controls ( P < 0.05). Muscle fatigue as a fraction of baseline peak isokinetic power was not different in COPD patients vs. controls (0.11 ± 0.20 vs. 0.19 ± 0.11). Baseline to intolerance, the median frequency of maximal isokinetic muscle activity, was unchanged in COPD patients but reduced in controls (+4.3 ± 11.6 vs. −5.5 ± 7.6%, P < 0.05). Performance fatigue as a fraction of peak incremental power was greater in COPD vs. controls and related to resting (FEV1/FVC) and peak exercise (V̇E/maximal voluntary ventilation) pulmonary function ( r2 = 0.47 and 0.55, P < 0.05). COPD patients are more fatigable than controls, but this fatigue is insufficient to constrain locomotor power and define exercise intolerance.

Rehabilitation Exercises for Dysfunction of the Scapula: Exploration of Muscle Activity Using Fine-Wire EMG

2021 ◽  
pp. 036354652110250
Author(s):  
Kelly R. Berckmans ◽  
Birgit Castelein ◽  
Dorien Borms ◽  
Thierry Parlevliet ◽  
Ann Cools
Keyword(s):  
Muscle Activity ◽  
Muscle Activation ◽  
Clinical Decision Making ◽  
External Rotation ◽  
Clinical Decision ◽  
Moderate Activity ◽  
Serratus Anterior ◽  
Maximal Voluntary Isometric Contraction ◽  
Forward Flexion ◽  
Muscle Balance

Background: Scapular muscle activity during shoulder exercises has been explored with surface electromyography (EMG). However, knowledge about the activity of deeper-layer scapular muscles is still limited. Purpose: To investigate EMG activation of the deeper-layer scapular stabilizers (levator scapulae [LS], rhomboid major [RM], pectoralis minor [Pm] muscles) together with superficial muscle activity (upper [UT], middle [MT], and lower trapezius [LT] and serratus anterior [SA]) during 4 exercises often used for training scapular function. Based on the amplitude EMG of the deeper-layer muscles, scapular muscle activation ratios for the 4 exercises were calculated, hereby providing knowledge of the optimal muscle balance. Study Design: Descriptive laboratory study. Methods: A total of 26 healthy participants performed 4 shoulder exercises (side-lying external rotation [ER], side-lying forward flexion, prone horizontal abduction with ER, and prone extension) while simultaneously measuring scapular muscle activity. Intramuscular electrodes were used for the deeper layer, in contrast to surface electrodes for the superficial muscles. All data were normalized to percentage of maximal voluntary isometric contraction (%MVIC), and the activation ratios (the muscle activity of the deeper layer relative to the other muscles) were calculated. A 1-way analysis of variance with Bonferroni correction was applied for statistical analysis. Results: Moderate activity was found in all exercises for the LS and RM (25%-45% MVIC). The Pm resulted in low activity during both side-lying exercises (13%-18% MVIC). Ratios involving LS or RM showed values >1 for all exercises (1.28-12.41) except for LS/MT, LS/LT, and LS/RM (0.85-0.98) during side-lying ER, and LS/MT, RM/MT and RM/LS (0.85-0.99) during side-lying forward flexion. Likewise, values <1 were found when MT (0.85) and LS (0.99) were involved with RM in the numerator during side-lying forward flexion. Ratios with Pm in the numerator showed values <1, apart from the ratios with UT and SA in the denominator. Conclusion: The study provides extended knowledge about the deeper-layer scapular muscle activity and related ratios during the 4 shoulder exercises mentioned here. Putting theory into practice, based on our results, we advise both side-lying exercises to be performed to strengthen LT and MT, even in case of hyperactivity of the Pm. However, the 4 exercises should be given carefully to patients with hyperactivity in the LS and/or RM. Clinical Relevance: The findings of this study may assist clinical decision making in exercise selection for restoring scapular function.

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