Scapulothoracic muscle activity during elevation exercises measured with surface and fine wire EMG: A comparative study between patients with subacromial impingement syndrome and healthy controls

Trapezius Muscle Electromyographic Activity in Lawn-Mower Exercise: Standing Versus Quadruped

CONTEXT

In shoulder rehabilitation, exercises that reduce upper trapezius (UT) activity and optimize the trapezius muscle activation rate reduce the symptoms of shoulder pathologies. One such exercise, the lawn-mower (LM) exercise, is frequently used in scapular rehabilitation protocols due to its multijoint, multiplanar, and kinetic chain-based nature. Design/Objective: This study aimed to compare trapezius muscle activation levels and ratios during the LM exercise in standing and quadruped positions through a randomized controlled trial.

METHODS

Eighteen healthy volunteers (mean age [SD] = 25 [5] y, 10 women and 8 men, mean body mass index [SD] = 22.91 [2.59] kg/m2) participated in the study, and surface electromyography was employed to measure trapezius muscle activity during quadruped LM (QLM) and standing LM (SLM) exercises. The data were normalized as a percentage of maximal voluntary contraction.

RESULTS

The study revealed significantly lower UT activity (percentage of maximal voluntary contraction) during QLM compared with SLM (P < .05) in concentric and isometric phases. Conversely, QLM exhibited significantly higher activation of the middle trapezius (MT) and lower trapezius (LT) in all phases when compared with SLM (P < .05). UT/MT and UT/LT ratios were also significantly lower in all QLM phases compared with SLM (P < .05).

CONCLUSION

Study findings suggest that quadruped exercises reduce UT activation while promoting more balanced MT and LT muscle activation. This balance is essential for shoulder rehabilitation, especially in cases requiring minimal UT activation and maximal MT and LT activation. In cases where a balanced trapezius muscle activation pattern is required, including QLM exercises rather than SLM exercises may be more efficient.

Innovative diagnostic framework for shoulder instability: a narrative review on machine learning-enhanced scapular dyskinesis assessment in sports injuries

A common shoulder problem that significantly detracts from patients' quality of life is shoulder instability (SI). Abnormal scapular positioning and movement are closely associated with rotator cuff injuries and SI, as shown by several studies. The aetiology of scapular dyskinesia (SD) adversely affects shoulder stability and function, including postural abnormalities, musculoskeletal problems, and neurological conditions. Presently, there is a paucity of studies on scapular kinetic alterations in SI rehabilitation. This paper rigorously examines the correlation between SI and scapular kinetic irregularities, as well as the functional alterations of periscapular muscle groups, offering a thorough theoretical foundation and practical guidance for clinicians to enhance their understanding of the disease mechanism and develop a more holistic and effective treatment for patients with SI. We examined the particular manifestations of scapular kinetic disorders in SI patients, evaluated current clinical assessment tools, and explored novel strategies (machine learning, kinetic chain, and scapular biomechanics) for prospective clinical applications. Our objective is to furnish a thorough theoretical foundation and practical guidance for rehabilitating patients with SI, thereby enhancing clinicians' comprehension of the disease mechanism and enabling the development of more effective rehabilitation programs.

The Clinical and Sonographic Features of Cervical Muscle Involvement in Patients with Frozen Shoulder: A Retrospective Study

Background/Objectives: Frozen shoulder is a common shoulder disorder that often places limitations on the range of motion of the shoulder. The disease may induce neck pain due to overuse of the neck muscle in an attempt to compensate for lack of shoulder movement. In clinical practice, swelling and inflammation of the scalene and levator scapulae may be detected via sonography in patients with frozen shoulder. The aim of this study was, therefore, to determine whether the involvement of the scalene complex or levator scapulae could compensate for the limited motion of the shoulder in patients with frozen shoulder. Methods: We retrospectively reviewed the medical records of 362 patients with unilateral frozen shoulder. These patients were divided into four groups depending on the involvement of the scalene complex or levator scapulae muscle. The range of motion of the shoulder-encompassing flexion, abduction, and external rotation-was measured with a goniometer. We also performed an ultrasound scan on each shoulder. The involvement of the scalene complex and levator scapulae muscle was also assessed via musculoskeletal ultrasound. Results: The range of motion of the shoulder in terms of flexion, abduction, external rotation, and total range of motion differed significantly between the four groups (p < 0.05). Patients in whom the scalene complex or levator scapulae muscle was involved demonstrated a significantly wider range of motion in different shoulder directions than patients without the involvement of those muscles (p < 0.05). Conclusions: A greater range of motion in the shoulder can be obtained through the activation of the scalene complex or levator scapulae muscle, which act to compensate for the lack of shoulder movement in patients with frozen shoulder. These two muscles showed thickening and hypoechoic changes upon sonography.

Electromyographic analysis of selected shoulder muscles during shoulder rehabilitation exercises in patients after reverse total shoulder arthroplasty

BACKGROUND

Reverse shoulder arthroplasty (RSA) aims to restore function in patients with rotator cuff failure and joint arthropathy. After surgery, patients are routinely referred to a rehabilitation specialist to regain range of motion, strength, and function. A key element in these programs is active exercises. The exercises are often selected based on assumed muscle activity, investigated by electromyography (EMG). In particular, in this patient population, activation of the deltoid and the scapular muscles is the focus of exercise therapy. Currently, most studies investigating muscle activity levels during exercises are performed on healthy individuals. To our knowledge, no study exists analyzing EMG activity during exercises in a population of shoulder arthroplasty patients. Therefore, the study aimed to analyze activity in the shoulder girdle muscles during 6 commonly used rehabilitation exercises 12 weeks after reverse shoulder arthroplasty surgery.

METHODS

Forty-four patients (50 shoulders) participated in this cross-sectional study, 12 weeks postoperatively (mean 99.18 ± 12.8 days), aged 68.9 ± 7.75 years. Surface EMG activity was measured in 10 shoulder girdle muscles: the 3 trapezius parts, serratus anterior, the 3 deltoid parts, latissimus dorsi, and 2 pectoralis major parts during 6 exercises, 3 in a closed chain, and 3 open chain elevation exercises.

RESULTS

Gravity-minimized exercises (horizontal plane) show low activity for almost all muscles. Vertical closed kinetic chain exercises show an increased activity compared to horizontal plane exercises. Open kinetic chain exercises against gravity showed the greatest activity in deltoid and upper trapezius. For the other muscles, no consistency in progression was found.

CONCLUSION

This study offers a progression of exercises for patients after reverse shoulder arthroplasty based on increased muscle activity.

Analysis of the three-dimensional scapular kinematics and associated scapular muscle activity during scapular muscle exercises

OBJECTIVE

To compare scapular kinematics and muscle activity among various scapular muscle exercises.

DESIGN

A cross-sectional study.

SETTING

A university research laboratory.

PARTICIPANTS

Eighteen healthy men participated in this study.

MAIN OUTCOME MEASURES

Three-dimensional scapular kinematics was measured with an electromagnetic motion capture system. Activities of the upper trapezius (UT), lower trapezius (LT), and serratus anterior (SA) were measured by using surface electromyography (EMG). In addition, the ratio of LT to the UT (LT/UT) and SA to the UT (SA/UT) was calculated. A repeated one-way analysis of variance and Shaffer's post-hoc analysis were used to detect the differences in each outcome during five exercises.

RESULTS

The scapula was rotated upwardly during all exercises except push-up plus. The LT/UT ratio during side-lying external rotation and side-lying flexion were significantly higher than that for scapular plane elevation (P < .05), although the highest activity of the lower trapezius was produced during scapular plane elevation. The activities of the serratus anterior and SA/UT ratio during horizontal adducted elevation and push-up plus were significantly higher than that during scapular plane elevation (P < .05).

CONCLUSION

Horizontal adducted elevation might be more appropriate for increasing scapular upward rotation with high serratus anterior activity and SA/UT ratio than push-up plus.

Measuring myofascial shear strain in chronic shoulder pain with ultrasound shear strain imaging: a case report

BACKGROUND

Dysfunctional gliding of deep fascia and muscle layers forms the basis of myofascial pain and dysfunction, which can cause chronic shoulder pain. Ultrasound shear strain imaging may offer a non-invasive tool to quantitatively evaluate the extent of muscular dysfunctional gliding and its correlation with pain. This case study is the first to use ultrasound shear strain imaging to report the shear strain between the pectoralis major and minor muscles in shoulders with and without chronic pain.

CASE PRESENTATION

The shear strain between the pectoralis major and minor muscles during shoulder rotation in a volunteer with chronic shoulder pain was measured with ultrasound shear strain imaging. The results show that the mean ± standard deviation shear strain was 0.40 ± 0.09 on the affected side, compared to 1.09 ± 0.18 on the unaffected side (p<0.05). The results suggest that myofascial dysfunction may cause the muscles to adhere together thereby reducing shear strain on the affected side.

CONCLUSION

Our findings elucidate a potential pathophysiology of myofascial dysfunction in chronic shoulder pain and reveal the potential utility of ultrasound imaging to provide a useful biomarker for shear strain evaluation between the pectoralis major and minor muscles.

Effects of manual therapy in addition to stretching and strengthening exercises to improve scapular range of motion, functional capacity and pain in patients with shoulder impingement syndrome: a randomized controlled trial

BACKGROUND

The current study aimed to measure the effectiveness of manual therapy in addition to stretching and strengthening exercises in patients with shoulder impingement syndrome to improve functional capacity, pain, and scapular range of motion.

METHODS

This is a single-blinded randomized controlled trial. Thirty-two participants with chronic shoulder impingement syndrome were randomly allocated into two groups. Both groups received stretching and strengthening exercises while the treatment group was given manual therapy additionally. Treatment was started after the patients signed an informed consent form. The data were collected from the University of Lahore Teaching Hospital between March 2022 and December 2022. The study aimed to measure pain using a numeric pain rating scale, functional capacity was assessed by the disability of the arm and shoulder, and goniometry was used for scapular ranges, i.e., scapular protraction and upward rotation. Each treatment session lasted 45 min for the treatment group and 30 min for the control group. The treatment comprised five days a week for four weeks, after which post-intervention measurements were taken.

RESULTS

Thirty-two participants were enrolled in the study, and 16 were divided into each group. The mean age of the participants in the treatment group was 38.19 ± 7.31 while the comparison group was 35.69 ± 7.98. An independent sample t-test was run on the data with a 95% confidence interval, statistically significant results were obtained, i.e., p-value < 0.05, post-intervention in the treatment group. Both groups have significantly improved functional capacity and scapular protraction (p < 0.005), however, pain and scapular upward rotation were not found statistically significant in the control group (p > 0.05).

CONCLUSION

The addition of manual therapy along with exercise therapy showed clinical and statistical significant results for pain, functional capacity, and scapular range of motion. It demonstrated superior effects than exercise therapy alone for the chronic condition of SIS.

TRIAL REGISTRATION

The trial was registered in the Iranian Registry of Clinical Trials ( https://www.irct.ir/ ) with the registration number: IRCT20230526058291N1, (Date: 12/08/2023).

Normal values of scapular muscle activity ratio during arm elevation and the relationship to muscle strength and sex difference

BACKGROUND

The normal value of the scapular muscle activity ratio during arm elevation is not clear.

OBJECTIVE

To obtain normal values of the scapular muscle activity ratio during arm elevation in healthy individuals.

METHODS

This cross-sectional study enrolled 47 healthy people. The participants performed shoulder flexion and lowered task with 90-degree movements every 2 seconds. Muscle activities of scapular muscles were measured. For normalization, the maximum isometric contraction of the shoulder flexion was measured at 90∘ (reference contraction). The integrated electromyographic value (IEMG) obtained during the task was normalized by IEMG during the reference contraction and the relative IEMG value was calculated. Then, the scapular muscle activity ratio was computed. The relationship between muscle strength and other factors was also investigated.

RESULTS

The median values for upper trapezius/serratus anterior and upper trapezius/lower trapezius were often approximately 1, and that for upper trapezius/middle trapezius was often between 1 and 2. The shoulder flexion isometric strength and scapular muscle activity ratio showed significant negative correlations in multiple phases.

CONCLUSION

Normal values for upper trapezius/serratus anterior and upper trapezius/lower trapezius during arm elevation and lowering were generally 1. Low muscle strength may contribute to an abnormal scapular muscle activity balance.

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.

Exercise for rotator cuff tendinopathy: Proposed mechanisms of recovery

Rotator cuff (RC) tendinopathy is a common recurrent cause of shoulder pain, and resistance exercise is the first-line recommended intervention. Proposed causal mechanisms of resistance exercise for patients with RC tendinopathy consist of four domains: tendon structure, neuromuscular factors, pain and sensorimotor processing, and psychosocial factors. Tendon structure plays a role in RC tendinopathy, with decreased stiffness, increased thickness, and collagen disorganization. Neuromuscular performance deficits of altered kinematics, muscle activation, and force are present in RC tendinopathy, but advanced methods of assessing muscle performance are needed to fully assess these factors. Psychological factors of depression, anxiety, pain catastrophizing, treatment expectations, and self-efficacy are present and predict patient-reported outcomes. Central nervous system dysfunctions also exist, specifically altered pain and sensorimotor processing. Resisted exercise may normalize these factors, but limited evidence exists to explain the relationship of the four proposed domains to trajectory of recovery and defining persistent deficits limiting outcomes. Clinicians and researchers can use this model to understand how exercise mediates change in patient outcomes, develop subgroups to deliver patient-specific approach for treatment and define metrics to track recovery over time. Supporting evidence is limited, indicating the need for future studies characterizing mechanisms of recovery with exercise for RC tendinopathy.

Kinematics and muscle activation in subacromial pain syndrome patients and asymptomatic controls

BACKGROUND

Conflicting theories exist about the underlying cause of chronic subacromial pain in the middle-aged population. We aim to improve our understanding of kinematics and muscle activation in subacromial pain syndrome to provide insight in its pathophysiology.

METHODS

In a cross-sectional comparison of 40 patients with subacromial pain syndrome and 30 asymptomatic controls, three-dimensional shoulder kinematics and electromyography-based co-contraction in 10 shoulder muscles were independently recorded. Glenohumeral and scapulothoracic kinematics were evaluated during abduction and forward flexion. Co-contraction was expressed as an activation ratio, specifying the relative agonistic and antagonistic muscle activity in each muscle.

FINDINGS

During abduction and forward flexion, the contribution of glenohumeral motion to elevation and glenohumeral external rotation was lower in subacromial pain syndrome (at 120⁰ abduction: -9°, 95% CI -14°- -3°; and - 8°, 95% CI -13°--3°, respectively), and was compensated by more scapulothoracic motion. The pectoralis major's activation ratio was significantly lower (Z-score: -2.657, P = 0.008) and teres major's activation ratio significantly higher (Z-score: -4.088, P < 0.001) in patients with subacromial pain syndrome compared to the control group.

INTERPRETATION

Reduced glenohumeral elevation and external rotation in subacromial pain syndrome coincided with less teres major antagonistic activity during elevation. These biomechanical findings provide a scientific basis for intervention studies directed at stretching exercises to reduce glenohumeral stiffness in the treatment of subacromial pain syndrome, and teres major strengthening to improve humeral head depressor function.

Physiotherapy Rehabilitation in Subjects Diagnosed with Subacromial Impingement Syndrome Does Not Normalize Periscapular and Rotator Cuff Muscle Onset Time of Activation

Clinicians suggest that rehabilitation of Subacromial Impingement Syndrome (SIS) should target improving movement patterns to ensure better clinical outcomes. Understanding changes in onset time of activation patterns and associated changes in clinical outcomes could improve our understanding of rehabilitation strategies. In this prospective longitudinal study, we examined neuromuscular firing patterns and clinical features before and after a standardized physiotherapy program in subjects diagnosed with SIS. Electromyography (EMG) recordings of eleven shoulder muscles were taken at the initial and discharge consultation in 34 male volunteers diagnosed with SIS. EMG recording was performed during flexion, scaption, and abduction at slow, medium, and fast speeds with a loaded (3 kg) and unloaded arm, as well as rotational motion, rotational strength, pain, and shoulder function. Completion of standardized shoulder physiotherapy program for SIS resulted in improvements in clinical outcomes. Resulted showed inconsistent differences of onset time of activation mainly in some of the periscapular muscles for all movements. No differences were seen on the EMG recordings for rotator cuff muscles. Differences in range of motion, strength and function were shown. Despite some changes in onset time of activation, this study was not able to demonstrate consistent changes of onset time of activation of the periscapular and rotator cuff muscles.

Quantification of muscles activations and joints range of motions during oil palm fresh fruit bunch harvesting and loose fruit collection

Although global demand for palm oil has been increasing, most activities in the oil palm plantations still rely heavily on manual labour, which includes fresh fruit bunch (FFB) harvesting and loose fruit (LF) collection. As a result, harvesters and/or collectors face ergonomic risks resulting in musculoskeletal disorder (MSD) due to awkward, extreme and repetitive posture during their daily work routines. Traditionally, indirect approaches were adopted to assess these risks using a survey or manual visual observations. In this study, a direct measurement approach was performed using Inertial Measurement Units, and surface Electromyography sensors. The instruments were attached to different body parts of the plantation workers to quantify their muscle activities and assess the ergonomics risks during FFB harvesting and LF collection. The results revealed that the workers generally displayed poor and discomfort posture in both activities. Biceps, multifidus and longissimus muscles were found to be heavily used during FFB harvesting. Longissimus, iliocostalis, and multifidus muscles were the most used muscles during LF collection. These findings can be beneficial in the design of various assistive tools which could improve workers' posture, reduce the risk of injury and MSD, and potentially improve their overall productivity and quality of life.

The Addition of Real-time Ultrasound Visual Feedback to Manual Facilitation Increases Serratus Anterior Activation in Adults With Painful Shoulders: A Randomized Crossover Trial

OBJECTIVE

Serratus anterior (SA) muscle activation may be decreased with subacromial pain syndrome. The purpose of this study was to determine whether the addition of real-time ultrasound (RTUS) visual feedback increased activation of SA in adults with painful shoulders in comparison to manual facilitation alone.

METHODS

This assessor-blinded, 2-period, randomized cross-over trial was conducted in a university medical imaging laboratory. Adults with mild-moderate unilateral subacromial pain received both interventions in random order with at least 1-week washout between interventions. Fourteen participants were randomized to receive manual facilitation with RTUS first, and 13 were randomized to receive manual facilitation alone first. Fifteen repetitions of a supine ``serratus punch'' were facilitated by RTUS visual feedback with manual facilitation or by manual facilitation alone. Levels of SA activation via surface electromyography were normalized to a maximum voluntary isometric contraction.

RESULTS

A total of 25 participants completed the full trial of both interventions. Data from 25 participant periods for RTUS with manual facilitation and data from 26 participant periods for manual facilitation only were analyzed. The predicted marginal mean difference between interventions was 55.5% (95% CI = 13.9% to 97.1%) in favor of the addition of RTUS feedback. No adverse effects occurred.

CONCLUSION

RTUS visual feedback increases SA activation in adults with painful shoulders compared with manual facilitation alone.

IMPACT

Determining if RTUS can improve SA muscle activation may help clinicians improve physical therapist interventions for subacromial pain syndrome.

Relative Scapular-Muscle Ratios During Maximal Isokinetic Shoulder-Girdle Strength Performance in Elite Field Hockey Players

CONTEXT

The shoulder joint and girdle are highly loaded during field hockey play. To optimize performance and to better substantiate preventive programs, it is important to gain insight into shoulder-girdle muscle function and balance in this athlete population.

OBJECTIVE

To evaluate relative scapular muscle-activity ratios through surface electromyography during maximal isokinetic strength testing in elite male field hockey players compared with nonathletes.

DESIGN

Cross-sectional study.

SETTING

Institutional laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twenty-five elite field hockey players from the Belgian National Team and 25 age- and sex-matched nonathletes.

INTERVENTION(S)

We measured bilateral activity in 4 scapular muscles (upper trapezius [UT], middle trapezius [MT], lower trapezius [LT], and serratus anterior [SA]) during an external-internal rotation and protraction-retraction isokinetic shoulder protocol.

MAIN OUTCOME MEASURE(S)

Relative scapular muscle-activity ratios, or balance ratios, of the UT : MT, UT : LT, UT : SA, SA : MT, and SA : LT.

RESULTS

We noted lower ratios bilaterally in the athlete group compared with the control group for the UT : MT, UT : LT, and SA : MT ratios during protraction, retraction, and external rotation, respectively, and unilaterally (dominant side only) for the UT : LT ratio during protraction. No consistent trend was present for established side differences in the studied balance ratios.

CONCLUSIONS

Compared with nonathletes, elite field hockey players had altered intramuscular (within the trapezius) and intermuscular (between the trapezius and SA) balance ratios during maximal shoulder-girdle contractions, with relatively more MT and LT activity. This may reflect a sport-specific adaptation to optimize coordinated activity of the scapulothoracic muscles, meeting the specific demands of field hockey movements and simultaneously better protecting the shoulder against injury. Our results can assist in optimizing high-performance training and in supporting injury-prevention programs, which are key to both successful and long-lasting athletic careers.

Análise eletromiográfica de músculos do complexo do ombro durante exercícios de rotação externa com faixa elástica

RESUMO Na artrocinemática do ombro, o manguito rotador atua estabilizando a cabeça umeral em contato com a cavidade glenoidal, enquanto realiza a translação inferior para contrabalancear a força rotacional promovida principalmente pelo deltoide. Exercícios de rotação externa (RE) vêm sendo utilizados na reabilitação de pacientes com disfunções no complexo do ombro buscando restaurar a artrocinemática. Porém, poucos estudos abordam a utilização da faixa elástica e a avaliação dos músculos da cintura escapular, determinantes para uma cinemática adequada. O objetivo deste estudo é comparar a atividade eletromiográfica (EMG) de músculos do complexo do ombro durante exercícios de rotação externa com faixa elástica. Participaram 11 sujeitos do sexo masculino que foram avaliados durante os movimentos de (1) RE em ortostase; (2) RE com abdução de ombro; (3) RE em decúbito lateral (DL). Os músculos avaliados pela EMG foram: (1) trapézio superior (TS); (2) deltoide médio (DM); (3) deltoide posterior (DP); e (4) infraespinal (IN). A resistência foi determinada por uma faixa elástica cinza calibrada com carga de 5% do peso corporal. A análise dos dados foi realizada no software Biomec-SAS e as estatísticas foram calculadas por meio da Anova de medidas repetidas no software SPSS v20.0. Pôde-se constatar que os músculos TS e DM obtiveram maior atividade EMG durante o exercício de RE com abdução de ombro, o músculo DP durante a RE com abdução de ombro e RE em decúbito lateral, enquanto o IN a obteve durante a RE em ortostase e RE em decúbito lateral.

Comparison of scapular muscle activation during shoulder elevation in older and young adults: A pilot study

BACKGROUND

The prevalence of degenerative shoulder disease is increasing, and most shoulder diseases are accompanied by changed activation of the scapular muscles. However, the characteristics of scapular muscle activation in older adults have not yet been reported.

OBJECTIVE

The aim of this study was to investigate the effect of age and load on scapular muscle activation during shoulder abduction and flexion.

METHODS

Eleven older adults (5 men, 6 women; 71.1 ± 5.3 years) and ten young adults (5 men, 5 women; 25.0 ± 2.7 years) performed shoulder elevation (abduction and flexion) with and without a dumbbell. Electromyography were recorded from the upper, middle and lower trapezius, and serratus anterior muscles in the dominant side. Muscle activation was normalized by reference voluntary contractions.

RESULTS

During shoulder elevation with a dumbbell load, the activation of the middle trapezius (p= 0.036) in older adults was significantly higher than that in young adults during abduction. The activation of the upper trapezius (p= 0.001) in older adults was significantly higher than that in young adults during flexion.

CONCLUSION

The older adults have a higher activation of the upper and middle trapezius during shoulder elevation with a weighted load.

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

BACKGROUND

Little is known about trapezius muscle activities during scapular retraction exercises in patients with subacromial impingement syndrome. The aim of this study was to compare upper trapezius, middle trapezius and lower trapezius muscle activity and upper/middle and upper/lower trapezius ratios between patients with subacromial impingement syndrome and healthy individuals during six scapular retraction exercises.

METHODS

Twenty-two patients with subacromial impingement syndrome and 22 healthy individuals participated. Upper, middle, and lower trapezius activities were measured by surface electromyography, while the participants performed six scapular retraction exercises at different shoulder abduction angles in a standing position. Upper/middle and upper/lower trapezius ratios were also calculated. Repeated-measures analyses of variance were performed to determine whether muscle activation levels and ratios differed between groups during exercises.

FINDINGS

There was no significant exercise × group interactions for upper, middle, and lower trapezius activation levels and upper/middle and upper/lower trapezius ratios (P > .05). A main effect for the exercise was observed for the upper/middle and upper/lower trapezius ratios (P < .05).

INTERPRETATION

Compared to healthy individuals, patients with subacromial impingement syndrome did not exhibit different upper, middle, and lower trapezius activity and had similar upper/middle and upper/lower trapezius ratios during the various scapular retraction exercises. Therefore, scapular retraction exercises with various shoulder abduction could be safely offered for the patients with subacromial impingement syndrome since it does not lead to abnormal compensatory trapezius muscle activity. If the goal is to minimize upper/middle and upper/lower trapezius ratios, the scapular retraction exercises at 0° shoulder abduction may be used in early stage of shoulder rehabilitation.

Scapular muscle dysfunction associated with subacromial pain syndrome

STUDY DESIGN

Narrative Review.

INTRODUCTION

One of the shoulder pain disorders in which the function of the scapula is comprised is the subacromial pain syndrome. Several rehabilitation guidelines and exercises have been proposed to improve scapulothoracic muscle dysfunction. Consideration of muscle activation patterns may help to select the most appropriate rehabilitation exercise in these patients. To date, suggesting rehabilitation exercises is often based upon the knowledge of the superficial lying scapulothoracic muscles' activity. In the assumption that the deeper lying scapulothoracic muscles' activity may hinder normal scapular movement in case of tightness or hyperactivity, exercise protocols for patients with altered pattern in scapulothoracic muscles should also integrate knowledge on the deeper lying scapulothoracic muscle activity.

PURPOSE OF THE STUDY

To help clinicians choosing the most appropriate exercise in patients with subacromial pain syndrome related to scapulothoracic muscle dysfunction.

METHODS

First, a summary of key alterations in scapulothoracic (muscle) function in patients with subacromial pain was accomplished. Second, promising practical rehabilitation strategies toward restoring scapulothoracic muscle dysfunction (with a focus on scapulothoracic exercises) were developed, integrating current new research evidence (including information about the deeper lying scapulothoracic muscles) with clinical practice.

CONCLUSION

This review details clinical exercises and their muscular activity to guide clinicians to optimize individualized scapulothoracic training and treatment programs by selecting the most appropriate exercise, based on knowledge from the clinical examination.

LEVEL OF EVIDENCE

Level 5.

Rotator cuff repair: post-operative rehabilitation concepts

PURPOSE OF REVIEW

With improvements in surgical techniques and increased knowledge of rotator cuff healing, there was a need to identify a safe progression after rotator cuff repair. The rehabilitation specialist plays an integral role in the care of these patients, and by implementing an evidence and criteria-based model, patients may be able to return to their prior levels of function sooner with fewer complications.

RECENT FINDINGS

Timing of progression for rotator cuff patients should align not only with healing but also potential strain on the involved tissue. Recent electromyography studies have identified exercises which elicit highest level of muscle activation for individual dynamic stabilizers. The physical therapist should also be aware of potential complications and be prepared to manage appropriately if they should arise. During rehabilitation after rotator cuff repair, there should be constant communication with the surgical team. Awareness of complication management, healing potential of the repaired tendon, and anatomy of the shoulder complex are critical. During the early stages, reducing pain and inflammation should be prioritized followed by progressive restoration of range of motion. When advancing range of motion, progression from passive, active assisted, and active movements allow for gradual introduction of stress to the healing construct. Even though time frames are not used for progression, it is important not to place excessive stress on the shoulder for up to 12 weeks to allow for proper tendon-to-bone healing. As exercises are progressed, scapular muscle activation is initiated, followed by isometric and lastly isotonic rotator cuff exercises. When treating overhead athletes, advanced strengthening in the overhead position is performed, followed by plyometric training. Advanced strengthening is initiated when all preceding criteria have been met. It is important that patients are educated early in the rehabilitation process so that they can manage their expectations to realistic time frames.

Electromyographic activity of the shoulder muscles during rehabilitation exercises in subjects with and without subacromial pain syndrome: a systematic review

BACKGROUND

Subacromial pain syndrome (SPS) is a common cause of shoulder pain and muscle activity deficits are postulated to contribute to the development and progression of the disorder. The purpose of this systematic review was to definitively determine whether evidence exists of differences in electromyography (EMG) characteristics between subjects with and without SPS.

METHODS

Six key databases were searched: MEDLINE, EMBASE, CINAHL, SPORTdiscus, PEDro and The Cochrane Library (inception to May 2016). The search yielded 1414 records using terms relating to shoulder impingement, EMG, scapular and rotator cuff muscles. Twenty-two papers remained once duplicates were removed and selection criteria applied. Data extraction, quality assessment and data synthesis were performed. Effect sizes and 95% confidence intervals were calculated.

RESULTS

There was limited evidence that serratus anterior has lower amplitude, delayed activation and earlier termination in SPS participants. For the majority of muscles, regardless of task, load or arm position, significant differences were not demonstrated or results were contradictory.

CONCLUSIONS

The understanding of SPS is changing and EMG appears unable to capture the complexities associated with this condition. Addressing aberrant movement patterns and facilitating balanced activation of all shoulder muscles may be a more appropriate treatment direction for the future.

The influence of induced shoulder muscle pain on rotator cuff and scapulothoracic muscle activity during elevation of the arm

BACKGROUND

Altered recruitment of rotator cuff and scapulothoracic muscles has been identified in patients with subacromial impingement syndrome. To date, however, the cause-consequence relationship between pain and altered muscle recruitment has not been fully unraveled.

METHODS

The effect of experimental shoulder pain induced by injection of hypertonic saline in the supraspinatus on the activity of the supraspinatus, infraspinatus, subscapularis, trapezius, and serratus anterior activity was investigated during the performance of an elevation task by use of muscle functional magnetic resonance imaging in 25 healthy individuals. Measurements were taken at 4 levels (C6-C7, T2-T3, T3-T4, and T6-T7) at rest and after the elevation task performed without and with experimental shoulder pain.

RESULTS

During arm elevation, experimentally induced pain caused a significant activity reduction, expressed as reduction in T2 shift of the IS (P = .029). No significant changes in T2 shift values were found for the other rotator cuff muscles or the scapulothoracic muscles.

CONCLUSIONS

This study demonstrates that acute experimental shoulder pain has an inhibitory effect on the activity of the IS during arm elevation. Acute experimental shoulder pain did not seem to influence the scapulothoracic muscle activity significantly. The findings suggest that rotator cuff muscle function (infraspinatus) should be a consideration in the early management of patients with shoulder pain.

Differences in the activation and co-activation ratios of the four subdivisions of trapezius between genders following a computer typing task

The aim of this study was to provide a description of gender differences of the activation patterns of the four subdivisions of the trapezius (clavicular, upper, middle, lower) following a 60min computer work task. Surface EMG was collected from these subdivisions from 21 healthy subjects during bilateral arm elevation pre-/post- task. Subjects completed a standardized 60min computer work task at a standard, ergonomic workstation. Normalized activation and activation ratios of each trapezius subdivision were compared between genders and condition with repeated measures ANOVAs. The interaction effect of Gender×Condition for upper trapezius% activation approached significance at p=0.051with males demonstrating greater activation post-task. The main effect of Condition was statistically significant for% activation of middle and lower trapezius (p<0.05), with both muscles demonstrating increase activation post-task. There was a statistically significant interaction effect of Gender×Condition for the Middle Trapezius/Upper Trapezius ratio and main effect of Condition for the Clavicular Trapezius/Upper Trapezius ratio, with a decreased ratio post-typing. Gender differences exist following 60min of a low force computer typing task. Imbalances in muscle activation and activation ratios following computer work may affect total shoulder kinematics and should be further explored.