scholarly journals An Electromyographic Study of the Hip Abductor Muscles as Subjects With a Hip Prosthesis Walked With Different Methods of Using a Cane and Carrying a Load

1999 ◽  
Vol 79 (12) ◽  
pp. 1163-1173 ◽  
Author(s):  
Donald A Neumann
Keyword(s):  
Body Weight ◽  
Muscle Activity ◽  
Hip Prosthesis ◽  
Load Condition ◽  
Surface Emg ◽  
Emg Activity ◽  
Emg Signal ◽  
Hip Abductor ◽  
Load Conditions

Abstract Background and Purpose. Certain methods of carrying handheld loads or using a cane can reduce the demands placed on the hip abductor (HA) muscles and the loads on the underlying prosthetic hip. In certain conditions, unusually large forces from the HA muscles may contribute to premature loosening of a prosthetic hip. The purpose of this study was to examine HA use by measuring the amplitude of the electromyographic (EMG) signal from the HA muscles as subjects carried a load and simultaneously used a cane. Subjects. Twenty-four active subjects (mean age=63.3 years, SD=10.7, range=40–86) with a unilateral prosthetic hip were tested. Methods. The HA muscle surface EMG activity was analyzed as subjects carried loads weighing 5%, 10%, or 15% of body weight held by either their contralateral or ipsilateral arm relative to their prosthetic hip. They simultaneously used a cane with their free hand. Results. The contralateral cane and ipsilateral load conditions produced HA muscle EMG activity that was approximately 40% less than the EMG activity produced while walking without carrying a load or using a cane. Conclusion and Discussion. People who are in danger of premature loosening of their prosthetic hip should, if possible, avoid carrying loads. If a load must be carried, however, then the contralateral cane and ipsilateral load condition appears to minimize the loads placed on the prosthetic hip due to HA muscle activity.

scholarly journals Semi-automated Detection of the Timing of Respiratory Muscle Activity: Validation and First Application

2022 ◽  
Vol 12 ◽  
Author(s):  
Antenor Rodrigues ◽  
Luc Janssens ◽  
Daniel Langer ◽  
Umi Matsumura ◽  
Dmitry Rozenberg ◽  
...  
Keyword(s):  
Muscle Activity ◽  
Respiratory Muscle ◽  
Respiratory Muscles ◽  
Failure Surface ◽  
Surface Emg ◽  
Emg Activity ◽  
Emg Signal ◽  
Activity Duration ◽  
Millisecond Accuracy ◽  
Respiratory Muscle Activity

Background: Respiratory muscle electromyography (EMG) can identify whether a muscle is activated, its activation amplitude, and timing. Most studies have focused on the activation amplitude, while differences in timing and duration of activity have been less investigated. Detection of the timing of respiratory muscle activity is typically based on the visual inspection of the EMG signal. This method is time-consuming and prone to subjective interpretation.Aims: Our main objective was to develop and validate a method to assess the respective timing of different respiratory muscle activity in an objective and semi-automated manner.Method: Seven healthy adults performed an inspiratory threshold loading (ITL) test at 50% of their maximum inspiratory pressure until task failure. Surface EMG recordings of the costal diaphragm/intercostals, scalene, parasternal intercostals, and sternocleidomastoid were obtained during ITL. We developed a semi-automated algorithm to detect the onset (EMG, onset) and offset (EMG, offset) of each muscle’s EMG activity breath-by-breath with millisecond accuracy and compared its performance with manual evaluations from two independent assessors. For each muscle, the Intraclass Coefficient correlation (ICC) of the EMG, onset detection was determined between the two assessors and between the algorithm and each assessor. Additionally, we explored muscle differences in the EMG, onset, and EMG, offset timing, and duration of activity throughout the ITL.Results: More than 2000 EMG, onset s were analyzed for algorithm validation. ICCs ranged from 0.75–0.90 between assessor 1 and 2, 0.68–0.96 between assessor 1 and the algorithm, and 0.75–0.91 between assessor 2 and the algorithm (p < 0.01 for all). The lowest ICC was shown for the diaphragm/intercostal and the highest for the parasternal intercostal (0.68 and 0.96, respectively). During ITL, diaphragm/intercostal EMG, onset occurred later during the inspiratory cycle and its activity duration was shorter than the scalene, parasternal intercostal, and sternocleidomastoid (p < 0.01). EMG, offset occurred synchronously across all muscles (p ≥ 0.98). EMG, onset, and EMG, offset timing, and activity duration was consistent throughout the ITL for all muscles (p > 0.63).Conclusion: We developed an algorithm to detect EMG, onset of several respiratory muscles with millisecond accuracy that is time-efficient and validated against manual measures. Compared to the inherent bias of manual measures, the algorithm enhances objectivity and provides a strong standard for determining the respiratory muscle EMG, onset.

One-trial adaptation of movement to changes in load

1996 ◽  
Vol 75 (1) ◽  
pp. 60-74 ◽  
Author(s):  
D. L. Weeks ◽  
M. P. Aubert ◽  
A. G. Feldman ◽  
M. F. Levin
Keyword(s):  
Equilibrium State ◽  
Joint Angle ◽  
Biceps Brachii ◽  
Isometric Force ◽  
Dominant Role ◽  
Load Condition ◽  
Emg Activity ◽  
Positional Error ◽  
Rapid Adaptation ◽  
Load Conditions

1. We analyzed the rapid adaptation of elbow movement to unexpected changes in external load conditions at the elbow joint. The experimental approach was based on the lambda model, which defines control variables (CVs) setting the positional frames of reference for recruitment of flexor and extensor motoneurons. CVs may be specified by the nervous system independently of the current values of output variable such as electromyographic (EMG) activity, muscle torques, and kinematics. The CV R specifies the referent joint angle (R) at which the transition of flexor to extensor activity or vice versa can be observed during changes in the actual joint angle, theta, elicited by an external force. The other CV, the coactivation (C) command, instead of a single transition angle, defines an angular range in which flexor and extensor muscles may be simultaneously active (if C > 0) or silent (if C < 0). Changes in the R command result in shifts in the equilibrium state of the system, a dynamic process leading to EMG modifications resulting in movement or isometric force production if movement is obstructed. Fast movements are likely produced by combining the R command with a positive C command, which provides movement stability and effective energy dissipation, diminishing oscillations at the end of movement. 2. According to the model, changes in the load characteristic (e.g., from a 0 to a springlike load) influence the system's equilibrium state, leading to a positional error. This error may be corrected by a secondary movement produced by additional changes in R and C commands. In subsequent trials, the system may reproduce the CVs specified after correction in the previous trial. This behavior is called the recurrent strategy. It allows the system to adapt to the new load condition in the subsequent trials without corrections (1-trial adaptation). Alternatively, the system may reproduce the CVs specified before correction (invariant strategy). If the movement was perturbed only in a single trial, the invariant strategy allows the system to reach the target in the subsequent trials without corrections. 3. To test the assumption on the dominant role of the recurrent strategy in rapid adaptation of movement to new load conditions, we performed experiments in which subjects (n = 6) used a pivoting manipulandum and made fast 60 degrees movements to a target. After a random number of trials (5-10) with no load, we introduced opposing (experiment 1), assisting (experiment 2), or randomly varied opposing or assisting loads (experiment 3) for 5-10 trials before unexpectedly switching loads again (14-18 switches in total). The opposing or assisting torque was created by position feedback to a torque motor and was a linear function of the displacement of the manipulandum form the initial position (springlike load). Subjects were instructed to correct positional errors as soon as possible to reach the target. The EMG activity of two elbow flexors (biceps brachii and brachioradialis) and two elbow extensors (triceps brachii and anconeus), elbow position, velocity, and torque were recorded. Kinematic and EMG patterns were compared with those obtained in similar experiments in which subjects were instructed not to correct errors. 4. In 94% of the trials in which a change in the load occurred, the primary movement was in error and was followed by a corrective secondary movement. In primary movements, both the phasic and tonic levels of EMG activity as well as the kinematics were load dependent, implicating reflex and intramuscular mechanisms in the adaptation of muscle forces counteracting external loads. These mechanisms, however, were not sufficient to eliminate positional errors. 5. An undershoot error occurred in trials with an opposing load after those with no load or in trials with no load after those with an assisting load. After adaptation to a new load condition, a sudden return to the previous load condition resulted in an error of the oppo

scholarly journals Low-Frequency Oscillations (<0.3 Hz) in the Electromyographic (EMG) Activity of the Human Trapezius Muscle During Sleep

2002 ◽  
Vol 88 (3) ◽  
pp. 1177-1184 ◽  
Author(s):  
R. H. Westgaard ◽  
P. Bonato ◽  
K. A. Holte
Keyword(s):  
Heart Rate ◽  
Muscle Activity ◽  
Activity Pattern ◽  
Sudden Change ◽  
Mean Amplitude ◽  
Activity Level ◽  
Emg Activity ◽  
Similar Frequency ◽  
Emg Signal ◽  
The Mean

The surface electromyographic (EMG) signal from right and left trapezius muscles and the heart rate were recorded over 24 h in 27 healthy female subjects. The root-mean-square (RMS) value of the surface EMG signals and the heartbeat interval time series were calculated with a time resolution of 0.2 s. The EMG activity during sleep showed long periods with stable mean amplitude, modulated by rhythmic components in the frequency range 0.05–0.2 Hz. The ratio between the amplitude of the oscillatory components and the mean amplitude of the EMG signal was approximately constant over the range within which the phenomenon was observed, corresponding to a peak-to-peak oscillatory amplitude of ∼10% of the mean amplitude. The duration of the periods with stable mean amplitude ranged from a few minutes to ∼1 h, usually interrupted by a sudden change in the activity level or by cessation of the muscle activity. Right and left trapezius muscles presented the same pattern of FM. In supplementary experiments, rhythmic muscle activity pattern was also demonstrated in the upper extremity muscles of deltoid, biceps, and forearm flexor muscles. There was no apparent association between the rhythmic components in the muscle activity pattern and the heart rate variability. To our knowledge, this is the first time that the above-described pattern of EMG activity during sleep is documented. On reanalysis of earlier recorded trapezius motor unit firing pattern in experiments on awake subjects in a situation with mental stress, low-FM of firing with similar frequency content was detected. Possible sources of rhythmic excitation of trapezius motoneurons include slow-wave cortical oscillations represented in descending cortico-spinal pathways, and/or activation by monoaminergic pathways originating in the brain stem reticular formation. The analysis of muscle activity patterns may provide an important new tool to study neural mechanisms in human sleep.

Use of a Shoulder Rest for Playing the Violin Revisited: An Analysis of the Effect of Shoulder Rest Height on Muscle Activity, Violin Fixation Force, and Player Comfort

2019 ◽  
Vol 34 (1) ◽  
pp. 39-46 ◽  
Author(s):  
Laura M Kok ◽  
Jim Schrijvers ◽  
Marta Fiocco ◽  
Barend van Royen ◽  
Jaap Harlaar
Keyword(s):  
Muscle Activity ◽  
Anterior Part ◽  
Activity Patterns ◽  
Deltoid Muscle ◽  
Surface Emg ◽  
Emg Activity ◽  
Linear Regression Models ◽  
Upper Trapezius ◽  
Shoulder Muscles ◽  
Rest Condition

AIMS: For violinists, the shoulder rest is an ergonomic adaptation to reduce musculoskeletal load. In this study, we aimed to evaluate how the height of the shoulder rest affects the violin fixation force and electromyographic (EMG) activity of the superficial neck and shoulder muscles. METHODS: In professional violinists, four different shoulder rest heights during five playing conditions were evaluated. Outcome variables included the jaw-shoulder violin fixation force and bilateral surface EMG of the upper trapezius (mTP), sternocleidomastoid (mSCM), and left anterior part of the left deltoid muscle (mDTA). Playing comfort was subjectively rated on a visual analogue scale (VAS). Linear regression models were estimated to investigate the influence of the shoulder rest height on muscle activity and violin fixation force as well as the muscle activity of the five evaluated muscles on violin fixation force. RESULTS: 20 professional violinists (4 males, 16 females, mean age 29.4 yrs) participated in this study. The shoulder rest condition had a significant effect on playing comfort (p<0.001), with higher shoulder rest conditions associated with decreased subjective playing comfort. The mean violin fixation force for each shoulder rest condition ranged between 2.92 and 3.39 N; higher shoulder rests were related to a higher violin fixation force (p<0.001). CONCLUSION: In this study, violin fixation force and muscle activity of the left mDTA increased while playing with an increasing height of the shoulder rest. As the shoulder rest influences muscle activity patterns and violin fixation force, adjustment of the shoulder rest and positioning of the violin need to be carefully optimized.

scholarly journals Effects of Sampling Frequency and Sample Window Size on Median Frequency of Surface EMG

2019 ◽  
Vol 63 (1) ◽  
pp. 1369-1372
Author(s):  
Pramiti Sarker ◽  
Gary Mirka
Keyword(s):  
Biceps Brachii ◽  
Window Size ◽  
Elbow Flexion ◽  
Surface Emg ◽  
Sampling Frequency ◽  
Emg Activity ◽  
Median Frequency ◽  
Surface Electrodes ◽  
Emg Signal ◽  
Sample Window

Muscle fatigue can be evaluated through the assessment of the downward shift in the median frequency (MDF) of the electromyographic (EMG) signal collected through surface electromyography. Previous research has shown that the value of MDF may be affected by sampling parameters. The purpose of this study was to quantify the combined effect of different sampling frequencies and window sizes on the calculated MDF. A sample of 24 participants performed a simple static elbow flexion exertion (15% MVC) and the EMG activity of the biceps brachii was periodically sampled using surface electrodes for four seconds at a frequency of 4096 Hz as the biceps brachii became fatigued. These collected data were then down-sampled to create a dataset of four window sizes (1s, 2s, 3s, and 4s) and five sampling frequencies (256 Hz, 512 Hz, 1024 Hz, 2048 Hz, and 4096 Hz). Median frequencies were calculated for each combination of sampling frequency and window size and then compared with the 4096 Hz / 4 s condition (considered gold standard) and the errors were calculated. Results suggest the use of a minimum sampling frequency of 512 Hz and a window size of 4s.

scholarly journals Alterations in Shoulder Kinematics and Associated Muscle Activity in People With Symptoms of Shoulder Impingement

2000 ◽  
Vol 80 (3) ◽  
pp. 276-291 ◽  
Author(s):  
Paula M Ludewig ◽  
Thomas M Cook
Keyword(s):  
Occupational Exposure ◽  
Muscle Activity ◽  
Load Condition ◽  
Trapezius Muscle ◽  
Electromyographic Activity ◽  
Serratus Anterior Muscle ◽  
Serratus Anterior ◽  
Shoulder Impingement ◽  
Upper Trapezius ◽  
Load Conditions

AbstractBackground and Purpose. Treatment of patients with impingement symptoms commonly includes exercises intended to restore “normal” movement patterns. Evidence that indicates the existence of abnormal patterns in people with shoulder pain is limited. The purpose of this investigation was to analyze glenohumeral and scapulothoracic kinematics and associated scapulothoracic muscle activity in a group of subjects with symptoms of shoulder impingement relative to a group of subjects without symptoms of shoulder impingement matched for occupational exposure to overhead work. Subjects. Fifty-two subjects were recruited from a population of construction workers with routine exposure to overhead work. Methods. Surface electromyographic data were collected from the upper and lower parts of the trapezius muscle and from the serratus anterior muscle. Electromagnetic sensors simultaneously tracked 3-dimensional motion of the trunk, scapula, and humerus during humeral elevation in the scapular plane in 3 hand-held load conditions: (1) no load, (2) 2.3-kg load, and (3) 4.6-kg load. An analysis of variance model was used to test for group and load effects for 3 phases of motion (31°–60°, 61°–90°, and 91°–120°). Results. Relative to the group without impingement, the group with impingement showed decreased scapular upward rotation at the end of the first of the 3 phases of interest, increased anterior tipping at the end of the third phase of interest, and increased scapular medial rotation under the load conditions. At the same time, upper and lower trapezius muscle electromyographic activity increased in the group with impingement as compared with the group without impingement in the final 2 phases, although the upper trapezius muscle changes were apparent only during the 4.6-kg load condition. The serratus anterior muscle demonstrated decreased activity in the group with impingement across all loads and phases. Conclusion and Discussion. Scapular tipping (rotation about a medial to lateral axis) and serratus anterior muscle function are important to consider in the rehabilitation of patients with symptoms of shoulder impingement related to occupational exposure to overhead work.

EMG Analysis of Patients with Unilateral Neck Pain

1999 ◽  
Vol 8 (1) ◽  
pp. 32-42 ◽  
Author(s):  
Robert L. Whalen ◽  
Steven P. Konstant ◽  
Teddy W. Worrell ◽  
Sam Kegerreis
Keyword(s):  
Neck Pain ◽  
Muscle Activity ◽  
Physical Therapist ◽  
Surface Emg ◽  
High Variability ◽  
Emg Activity ◽  
Upper Trapezius ◽  
Visual Analog Scales ◽  
Vas Scores ◽  
Emg Electrodes

The purpose of this study was to determine whether differences exist in EMG activity between involved and uninvolved upper trapezius muscles in participants with unilateral neck pain. Thirteen volunteers, seen by a physical therapist, gave informed consent. Surface EMG electrodes were placed on involved and uninvolved upper trapezius muscles. Root mean squared EMG activity was measured. Visual analog scales (VASs) for pain were used for each side. Reliability data indicated high ICC (2,1) but also large SEMs and CVs. EMG activity increased from resting to shrugging to abducting positions. Participants perceived greater pain on the involved side than the uninvolved side. EMG readings for individuals were consistent, however, between participants. EMG had high variability. Although participants' VAS scores were consistent with their reports of unilateral neck pain, surface EMG readings did not support the existence of increased muscle activity on the involved side.

scholarly journals Quantification of the Differences in Electromyographic Activity Magnitude Between the Upper and Lower Portions of the Rectus Abdominis Muscle During Selected Trunk Exercises

2001 ◽  
Vol 81 (5) ◽  
pp. 1096-1101 ◽  
Author(s):  
Gregory J Lehman ◽  
Stuart M McGill
Keyword(s):  
Muscle Activity ◽  
Abdominal Muscle ◽  
Rectus Abdominis ◽  
Oblique Muscle ◽  
Emg Activity ◽  
Electromyographic Activity ◽  
Rectus Abdominis Muscle ◽  
Emg Signal ◽  
External Oblique Muscle ◽  
External Oblique

Abstract Background and Purpose. Controversy exists around exercises and clinical tests that attempt to differentially activate the upper or lower portions of the rectus abdominis muscle. The purpose of this study was to assess the activation of the upper and lower portions of the rectus abdominis muscle during a variety of abdominal muscle contractions. Subjects. Subjects (N=11) were selected from a university population for athletic ability and low subcutaneous fat to optimize electromyographic (EMG) signal collection. Methods. Controlling for spine curvature, range of motion, and posture (and, therefore, muscle length), EMG activity of the external oblique muscle and upper and lower portions of rectus abdominis muscle was measured during the isometric portion of curl-ups, abdominal muscle lifts, leg raises, and restricted or attempted leg raises and curl-ups. A one-way repeated-measures analysis of variance was used to test for differences in activity between exercises in the external oblique and rectus abdominis muscles as well as between the portions of the rectus abdominis muscle. Results. No differences in muscle activity were found between the upper and lower portions of the rectus abdominis muscle within and between exercises. External oblique muscle activity, however, showed differences between exercises. Discussion and Conclusion. Normalizing the EMG signal led the authors to believe that the differences between the portions of the rectus abdominis muscle are small and may lack clinical or therapeutic relevance.

scholarly journals Optimized Hip-Knee-Ankle Exoskeleton Assistance Reduces the Metabolic Cost of Walking With Worn Loads

2021 ◽  
Author(s):  
Gwendolyn M Bryan ◽  
Patrick Franks ◽  
Seungmoon Song ◽  
Ricardo Reyes ◽  
Meghan O’Donovan ◽  
...  
Keyword(s):  
Body Weight ◽  
Muscle Activity ◽  
Metabolic Cost ◽  
Load Carriage ◽  
Heavy Load ◽  
Human In The Loop ◽  
Light Load ◽  
Wide Range ◽  
Ankle Exoskeleton ◽  
Load Conditions

Abstract BackgroundLoad carriage is a typical activity in a wide range of professions, but prolonged load carriage is associated with increased fatigue and overuse injuries. Exoskeletons could improve the quality of life of these professionals by reducing metabolic cost to combat fatigue and reducing muscle activity to prevent injuries. Current exoskeletons have reduced the metabolic cost of loaded walking by up to 23% when assisting one or two joints. Greater metabolic reductions may be possible with optimized assistance of the entire leg. MethodsWe used human-in the-loop optimization to optimize hip-knee-ankle exoskeleton assistance with no additional load, a light load (15% of body weight), and a heavy load (30% of body weight) for three participants. All loads were applied through a weight vest with an attached waist belt. We measured metabolic cost, exoskeleton assistance, kinematics, and muscle activity. We performed one-tailed paired t-tests to determine significant reductions for metabolic cost and muscle activity, and we performed an analysis of variance (ANOVA) to determine significant changes across load conditions for metabolic cost and applied power. ResultsExoskeleton assistance reduced the metabolic cost of walking relative to walking in the device without assistance for all tested conditions. Exoskeleton assistance reduced the metabolic cost of walking by 47% with no load (p = 0.02), 35% with the light load (p = 0.03), and 43% with the heavy load (p = 0.02). The smaller metabolic reduction with the light load may be due to insufficient participant training or lack of optimizer convergence. The total applied positive power was similar for all tested conditions, and the positive knee power decreased slightly as load increased. Optimized torque timing parameters were consistent across participants and load conditions while optimized magnitude parameters varied. ConclusionsWhole-leg exoskeleton assistance can reduce the metabolic cost of walking while carrying a range of loads. The consistent optimized timing parameters suggest that metabolic cost reductions are sensitive to torque timing. The variable torque magnitude parameters could imply that torque magnitude should be customized to the individual, or that there is a range of useful torque magnitudes. Future work should test whether applying the load to the exoskeleton rather than the person's torso results in larger benefits.

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