Trapezius muscle activation levels and ratios during scapular retraction exercises: A comparative study between patients with subacromial impingement syndrome and healthy controls

Electromyographic comparison of exercises for scapulothoracic muscle activation in men with upper crossed syndrome: A cross-sectional study

OBJECTIVE

This study aimed to determine the optimal exercise for improving Upper Crossed Syndrome (UCS) using electromyographic (EMG) activity of upper trapezius (UT), middle trapezius (MT), lower trapezius (LT), and serratus anterior (SA) during ten exercises.

METHOD

A cross-sectional study involved 30 male students (mean age: 25.3 ± 2.5 years; height: 176.8 ± 7.2 cm; weight: 77.7 ± 2.5 kg; BMI: 23.8 ± 0.72 kg/m2) with UCS. Participants were selected based on postural assessments (forward head posture ≥44°, rounded shoulder ≥49°, thoracic kyphosis ≥42°). EMG was used to measure activation levels of UT, MT, LT, and SA, and the UT activation ratio relative to MT, LT, and SA during ten exercises. One-way ANOVA was applied for data analysis.

RESULTS

Side-lying external rotation, standing diagonal flexion with Thera-band, and lying prone "V" demonstrated the least UT activity, with the highest MT and LT activation. The standing diagonal flexion with Thera-band elicited the highest SA activity. UT/MT, UT/LT, and UT/SA ratios were less than one in multiple exercises. Significant differences in muscle activation levels and ratios were observed across all exercises (P ≤ 0.05).

CONCLUSION

The findings suggest significant clinical implications for UCS rehabilitation. The identified exercises effectively engage MT and LT while minimizing UT activation, addressing muscular imbalances. Favorable UT/MT, UT/LT, and UT/SA ratios further support these exercises in correcting UCS. These exercises may help counteract the underlying muscular imbalance in UCS by promoting a more balanced activity ratio among the shoulder girdle muscles, potentially improving posture and reducing UCS symptoms.

Effects of scapulo-humeral training on ultrasonographic and clinical evaluations in stroke: a randomized controlled trial

BACKGROUND

After stroke, the effects of focused scapulo-humeral training with simultaneous assessment of the changes in shoulder subluxation, related muscle thicknesses and upper limb performance have not been studied in the literature.

OBJECTIVES

This study aimed to investigate the effects of an 8-week scapulo-humeral training program in addition to conventional rehabilitation on upper extremity/trunk functions, shoulder pain, and sonographic measurements of the shoulder joint and periscapular muscles.

METHODS

Thirty stroke individuals were randomly separated into two groups as Group I-scapulo-humeral training (5F/10 M) and Group II - control (5F/10 M). Conventional rehabilitation program was applied to both groups, and a scapulo-humeral training exercise protocol was added for the scapulo-humeral group. All the treatments were applied for 1 hour/day, 3 days/week, 8 weeks. Clinical evaluations were made using the Fugl Meyer Assessment-Upper Extremity(FMA-UE), Action Research Arm Test(ARAT), ABILHAND, Visual Analog Scale, and Trunk Impairment Scale(TIS). Ultrasound was used to measure serratus anterior/lower trapezius muscle thicknesses, and acromion-greater tubercule/acromio-humeral distances.

RESULTS

FMA-UE, ARAT, ABILHAND and TIS scores increased in both groups, with greater increases in most parameters in the scapulo-humeral training group. Shoulder pain decreased only in the scapulo-humeral training group. Subacromial distances were decreased on the paretic side, and muscle thicknesses increased on both sides in the scapulo-humeral training group, and in the control group, only serratus anterior muscle thickness increased on the paretic side (p < 0.05 for all).

CONCLUSIONS

Additional scapulo-humeral exercises to conventional rehabilitation was seen to improve upper extremity/trunk performance and shoulder pain, and to increase scapula stabilizer muscle thicknesses in stroke individuals with mild-moderate upper extremity disability.

Effectiveness of specific scapular therapeutic exercises in patients with shoulder pain: a systematic review with meta-analysis

Background

Therapeutic exercise has been considered a useful tool to rehabilitate shoulder pain, namely through its influence on scapular dynamics. Accordingly, the effectiveness of scapular therapeutic exercise needs to be explored. The present study aims to evaluate the effectiveness of scapular therapeutic exercises in shoulder pain and to identify the most effective exercise type (focal or multijoint) and ways of delivering them (as dose and progression).

Methods

Search was conducted at EMBASE, Cochrane Library, MEDLINE via PubMed, Web of Science, PEDro (Physiotherapy Evidence Database), and trial registration databases. The meta-analysis considered randomized controlled/crossover trials that compared the effect of scapular exercises against other types of intervention in the shoulder pain, shoulder function, scapular motion, and/or muscular activity. The risk of bias was assessed through the PEDro scale.

Results

From the 8318 records identified, 8 (high to low risk of bias- scoring from 4 to 8 on the PEDro scale) were included. The overall data, before sensitivity analysis, indicated that the scapular therapeutic exercises are: a) more effective than comparators in improving shoulder function (standardized mean difference [SMD] = 0.52 [95% Cl: 0.05, 0.99], P = .03, I2 = 76%); and b) as effective as comparators in reducing shoulder pain (SMD = 0.32 [95% Cl: -0.09, 0.73], P = .13, I2 = 70%). Subgroup analysis revealed that scapular exercises are more effective in improving shoulder function when the program duration is equal to or higher than 6 weeks (SMD = 0.43 [95% Cl: 0.09, 0.76] P = .01, I2 = 21%) and/or when the maximum number of exercise repetitions per session is lower than 30 (SMD = 0.79 [95% Cl: 0.15, 1.42], P = .01, I2 = 77%). Only 1 study considered scapular motion as an outcome measure, revealing therapeutic exercise effectiveness to improve scapular range of motion.

Conclusions

Intervention programs involving scapular therapeutic exercises are effective in improving shoulder function, presenting benefits when performed for 6 or more weeks and/or when used up to a maximum of 30 repetitions per exercise, per session.

Investigation of muscle activation during kinetic chain based exercises in individuals with and without forward head posture

BACKGROUND

The Band Pull-Apart (BPA) exercise is used to strengthen the periscapular muscles. It was recently stated that the lower extremity and trunk movements should be included in the shoulder rehabilitation programs to optimize an effective energy transfer throughout the kinetic chain.

OBJECTIVE

The aim of this study is to investigate the effects of kinetic chain based BPA exercise on the muscle activations of the sternocleidomasteideous (SCM) and the trapezius muscles in individuals with and without forward head posture (FHP).

METHODS

Eighteen individuals with FHP and 18 individuals without FHP were included. Photographic measurements were made to identify individuals with FHP. The muscle activations of SCM, Upper Trapezius (UT), Middle Trapezius (MT), and Lower Trapezius (LT) were measured with surface EMG. BPA exercise was performed in the standing, unipedal standing, squat, unipedal squat, and Bulgarian split squat (BSS).

RESULTS

There was no Group × Exercise interaction for the SCM, UT, MT, LT muscle activations, or for the UT/MT and UT/LT ratios (p> 0.05). While there was a difference in the activation of all muscles between individuals with and without FHP (p< 0.05), both ratios were similar (p> 0.05). There was a statistically significant difference between exercises for SCM, MT, and LT muscle activations (p< 0.000 for these muscles), UT/MT (p< 0.000) and UT/LT ratios (p= 0.004). SCM muscle activation in squat was lower than activation in standing (Mean Difference (MD) = 2.5% Maximal Voluntary Isometric Contractions (MVIC); p= 0.004) and in unipedal standing (MD = 2.1% MVIC; p= 0.002). MT muscle activation in squat was higher than activation in standing (MD = 9.7% MVIC), unipedal standing (MD = 7.8% MVIC), unipedal squat (MD = 6.9% MVIC) and BSS (MD = 9.4% MVIC; p< 0.000 for these positions). LT muscle activation in the squat was higher than activation in the standing (MD = 8.5% MVIC) and unipedal squat (MD = 8.1% MVIC; p< 0.004 for these positions). UT/MT ratio in the squat was lower than standing (MD = 0.3), unipedal standing (MD = 0.2) and BSS (MD = 0.3; p< 0.000 for these positions). UT/LT ratio in squat was lower than unipedal squat (MD = 0.5) and BSS (MD = 0.6; p= 0.002; for these positions).

CONCLUSION

Performing the BPA exercise in the squat position is suggested in cases where lower SCM and UT muscle activation, lower UT/MT, and UT/LT ratios and higher MT and LT muscle activations are needed for individuals with and without FHP.

Utilizing Scapula Retraction Exercises With or Without Glenohumeral Rotational Exercises With a Gradual Progression for Subacromial Pain Syndrome

BACKGROUND

Although exercise interventions are recommended in the management of subacromial pain syndrome (SPS), there is a lack of data regarding the exercises focusing on the principal biomechanical deficiencies that cause symptoms.

HYPOTHESIS

Utilizing progressive scapula retraction exercises (SRE) and glenohumeral rotation exercises (GRE) in the scapula stabilization program may lead to more reduction in symptoms and greater acromiohumeral distance (AHD) values.

STUDY DESIGN

A double-blind, randomized controlled trial.

LEVEL OF EVIDENCE

Level 2.

METHODS

A total of 33 patients were assigned randomly to either SRE or SRE+GRE. Both groups received a 12-week supervised rehabilitation program, including manual therapy and exercises (stretching and progressive scapula stabilization exercises). In addition, the SRE+GRE group performed GRE exercises at gradual elevation angles. From 12 to 24 weeks, patients performed exercise programs less frequently (3 times per week). Disability (shoulder pain and disability index [SPADI]), AHD (at 5 active abduction angles), pain intensity (visual analogue scale [VAS]), and patient satisfaction were recorded at baseline, 12 weeks, and 24 weeks. A total of 16 healthy individuals were recruited as a control group to compare AHD values. Data were analyzed using mixed model analyses of variance.

RESULTS

A statistically significant group-by-time interaction was found for AHD values (F4,92 = 6.38; P = 0.001), a significant group-by-time interaction for SPADI-disability (F1,33 = 5.148; P = 0.01), SPADI-total (F1,32 = 4.172; P = 0.03), and for pain during activity (F2,62 = 3.204; P = 0.05). However, no significant group-by-time interaction for SPADI-pain (F1,33 = 0.533; P = 0.48), for pain at rest (F1,31 < 0.001; P = 0.99), and at night (F1,32 = 2.166; P = 0.15). Yet, a significant time effect was observed.

CONCLUSION

Progressive SRE and GRE in the scapula stabilization program lessens symptoms and improves AHD values in patients with SPS. Moreover, this program could preserve outcomes and further increase AHD when applied less frequently.

CLINICAL RELEVANCE

Utilizing SRE and GRE in the scapula stabilization program at gradual shoulder abduction angles provides better rehabilitation outcomes.

Kinematic, electromyographic and isokinetic measurements for the management of shoulder subacromial pain syndrome: A systematic review

BACKGROUND

Subacromial shoulder pain syndrome is a very common and challenging musculoskeletal disorder. Kinematics, electromyographic muscle activity and isokinetic dynamometry are promising non-invasive movement analysis tools to improve understanding of this condition. No review has combined their results to provide a better understanding of the effects of subacromial pain syndrome on shoulder movement. This systematic review aimed to synthesise the associations between exposure to shoulder pain due to subacromial pain syndromes or subacromial impingement and changes in shoulder movement measures.

METHODS

The databases were Scholar google, Pubmed, Science Direct, Scopus and the Cochrane Library. We included studies that observed the association of the presence of subacromial pain syndromes or subacromial impingement with changes in shoulder motion measures.

FINDINGS

Seventeen studies with 943 participants were included. The main kinematic change was a lower scapular posterior during abduction in the subacromial pain syndrome group with a "low" level of evidence (standardised mean difference = -0.61, 95% confidence interval [-0.80; -0.43]). The main electromyographic change was an earlier onset of activation of the upper trapezius in the subacromial pain syndrome group, with a "moderate" level of evidence (standardised mean difference = 1.01, 95% confidence interval: [-2.97; 0.96]). The main isokinetic change was a lower peak internal rotator torque in the subacromial pain syndrome group, with a 'low' level of evidence (standardised mean difference = -0.41, 95% confidence interval: [-0.53; -0.29]).

INTERPRETATION

The variables measured during movement are associated with subacromial pain syndrome or subacromial impingement syndrome. Consistency between the results supports the importance of scapula biomechanics measurements in these conditions.

The influence of shoulder position during multi-joint exercises in the relative scapular muscles activity in symptomatic and asymptomatic conditions

BACKGROUND

Scapular muscles changes, as increased upper trapezius activity and decreased middle and lower trapezius and serratus anterior muscle activity, have been demonstrated in shoulder pain specific or non-specific conditions. Shoulder external rotation exercises have been recommended to improve scapular activity in shoulder pain.

OBJECTIVE

To evaluate the relative scapular muscles activity during multi-joint exercises combining shoulder external rotation, trunk rotation and scapular squeeze.

METHODS

Forty-one participants with and without shoulder pain were assessed in a cross-sectional study. They performed isometric multi-joint exercises at 0∘ and 90∘ of shoulder abduction with and without support. The relative activity of upper, middle, and lower trapezius and serratus anterior (upper/middle and lower portions) was measured through electromyography. The scapular muscular balance was assessed by the ratio between relative activity of the upper trapezius and the other muscles.

Shoulder structure and function: The impact of osteoarthritis and rehabilitation strategies

STUDY DESIGN

Invited review.

BACKGROUND

Shoulder osteoarthritis can result in significant functional deficits. To improve diagnosis and treatment, we must better understand the impact of osteoarthritis on shoulder biomechanics and the known mechanical benefits of currently available treatments.

PURPOSE

The purpose of this paper is to present up-to-date data on the effects of osteoarthritis and rehabilitation on the biomechanical parameters contributing to shoulder function. With this goal, we also reviewed the anatomy and the ranges of motion of the shoulder.

METHODS

A search of electronic databases was conducted. All study designs were included to inform this qualitative, narrative literature review.

RESULTS

This review describes the biomechanics of the shoulder, the impact of osteoarthritis on shoulder function, and the treatment of shoulder osteoarthritis with an emphasis on rehabilitation.

CONCLUSIONS

The shoulder is important for the completion of activities of daily living, and osteoarthritis of the shoulder can significantly reduce shoulder motion and arm function. Although shoulder rehabilitation is an integral treatment modality to improve pain and function in shoulder osteoarthritis, few high-quality studies have investigated the effects and benefits of shoulder physical and occupational therapies. To advance the fields of therapy and rehabilitation, future studies investigating the effects of therapy intensity, therapy duration, and the relative benefits of therapy subtypes on shoulder biomechanics and function are necessary.

Scapular Dynamic Muscular Stiffness Assessed through Myotonometry: A Narrative Review

Several tools have been used to assess muscular stiffness. Myotonometry stands out as an accessible, handheld, and easy to use tool. The purpose of this review was to summarize the psychometric properties and methodological considerations of myotonometry and its applicability in assessing scapular muscles. Myotonometry seems to be a reliable method to assess several muscles stiffness, as trapezius. This method has been demonstrated fair to moderate correlation with passive stiffness measured by shear wave elastography for several muscles, as well as with level of muscle contraction, pinch and muscle strength, Action Research Arm Test score and muscle or subcutaneous thickness. Myotonometry can detect scapular muscles stiffness differences between pre- and post-intervention in painful conditions and, sometimes, between symptomatic and asymptomatic subjects.

Overhead Shoulder Position Versus Scapular Retraction Position to Normalize the Electromyographic Signal of the Lower Trapezius Muscle

This study aimed to compare electromyographic response of the lower trapezius muscle during maximal voluntary isometric contractions under two conditions: overhead shoulder position versus scapular position, rating the pain after each condition. Twenty-six participants with shoulder pain (SP; n = 15; Shoulder Pain and Disability Index-Pain = 34 [range 6-66]) and without shoulder pain (nSP; n = 11; Shoulder Pain and Disability Index-Pain = 0 [range 0-14]) performed maximal voluntary isometric contractions in those 2 conditions while the lower trapezius was monitored using surface electromyography. Pain was rated using the visual analog scale. The nSP group experienced no pain, whereas the SP group reported pain in both conditions with higher pain during the overhead movement. No differences were observed for muscle excitation between conditions, but higher levels were observed for the nSP group compared with the SP group. The overhead condition was more painful for the SP group (visual analog scale: SP = 4 vs nSP = 1.09, P = .036). Scapular position showed the same levels of LT excitation than overhead position. The scapular position is preferable, compared with overhead positioning, to normalize the lower trapezius instead of overhead positioning.

Scapular Retraction under Adduction Load: An Alternative to Overhead Exercises to Activate Infraspinatus, Upper, and Lower Trapezius in Subjects with and without Shoulder Pain

Exercises for lower trapezius (LT) often use overhead positions, causing compressive forces to the subacromial space. Scapular retraction would be an alternative to activate LT muscle. The present study aimed to assess the excitation levels of infraspinatus, upper trapezius, and lower trapezius muscles during a scapular retraction exercise under progressive adduction loads in subjects with and without painful shoulder. Electromyography of infraspinatus (IS), upper trapezius (UT), and LT was recorded during scapular retraction under progressive adduction loads of 42 participants, divided into two groups: with (SP, n = 26) and without shoulder pain (nSP, n = 16). The adduction loads of 20%, 30%, 40%, and 50% of the maximal voluntary contraction (MVC) were applied using a load cell. Normalized electromyography and the ratio between UT and LT (UT:LT) were used for statistical analysis. No differences were observed between groups, but a condition effect occurred for all muscles: UT showed higher values at 50% vs. 20% of MVC (p = 0.004); LT showed higher values on 40% and 50% of MVC (p = 0.001; 0.006). Higher values for IS were noted at 40% of MVC (vs. 20% of MVC; p = 0.04) and at 50% of MVC (vs. 20% of MVC; p = 0.001, vs. 30% of MVC, p = 0.001; vs. 40% of MVC; p = 0.001). UT:LT showed lower values at 50% of MVC (vs. 20% of MVC; p = 0.001 and vs. 30% of MVC; p = 0.016). Scapular retraction with adduction loads at 40-50% is an alternative to overhead exercises aiming to activate the LT and the IS muscles. The exercise ensures higher levels of LT and IS excitation without increasing UT excitation.

Recruitment of Shoulder Complex and Torso Stabilizer Muscles With Rowing Exercises Using a Suspension Strap Training System

BACKGROUND

Suspension training systems, which use body weight resistance under unstable conditions, may be effective for muscle strengthening in persons with scapular dyskinesis or subacromial impingement syndrome.

HYPOTHESIS

Greater arm, scapular, and trunk muscle recruitment will occur during horizontal abduction row exercises.

STUDY DESIGN

Descriptive laboratory study.

LEVEL OF EVIDENCE

Level 5.

METHODS

Surface electromyography data were collected from 28 participants (14 men, 14 women). A total of 13 right-sided muscles were studied at a sampling frequency of 1000 Hz. Maximal voluntary isometric contractions (MVICs) were established. Participants completed 3 repetitions per exercise in random order. We compared muscle recruitment during 3 rowing exercises: low row, high row, and horizontal abduction row. Data were compared with repeated-measures analyses of variance and post hoc Bonferroni corrections.

RESULTS

For high row and horizontal abduction row conditions, the upper, middle, and lower trapezius and posterior deltoid demonstrated >60% MVIC magnitudes of recruitment, and the upper erector spinae demonstrated 40% to 60% MVIC magnitudes of recruitment, respectively. In contrast, in the low row exercise, 40% to 60% MVIC magnitudes of recruitment were observed only in the middle trapezius, latissimus dorsi, and posterior deltoid.

CONCLUSION

With the suspension system, high row and horizontal abduction row exercises promote muscle strengthening (>50% MVIC) in the upper, middle, and lower fibers of the trapezius, posterior deltoid, and upper erector spinae.

CLINICAL RELEVANCE

Rowing exercises performed with suspension straps may be recommended for muscle strengthening in patients with scapular dyskinesis and subacromial impingement syndrome as well as for healthy persons in need of enhanced scapular muscle performance.

Do surface electrodes validly represent lower trapezius activation patterns during shoulder tasks?

Because of its superficial location, surface electrodes are commonly used to record lower trapezius activity. Recent evidence, however, would suggest that surface electromyography is not a valid to record activity from other superficially placed shoulder muscles. Therefore, the aim of this study was to determine the validity of using surface electrodes to record lower trapezius activity. Ten asymptomatic subjects performed ramped isometric (0-100% maximum load) and dynamic (70% maximum load) shoulder tasks. Intramuscular electrodes were inserted into lower trapezius and rhomboid major. Surface electrodes were placed over lower trapezius around the intramuscular electrodes. Differences in the recorded activity of lower trapezius between surface and intramuscular electrodes were tested using a 2 factor repeated measures analysis of variance with factors: test and electrode type. Similarity in the recorded activity patterns between the two electrodes was tested using Pearson's correlation coefficient (r). Results indicated that there was no difference in lower trapezius activity levels (p = 0.98) or activation patterns (r ≥ 0.74) recorded by the intramuscular and surface electrodes. The results of this study indicate that any potential crosstalk contamination in the surface electrode signal is having little influence on the recorded activity from lower trapezius and therefore, support the common practice of surface electromyography to investigate lower trapezius function.