Glenohumeral Muscles Research Articles

Effects of Tear-Associated Scapula Shape on the Stabilizing Potential of Glenohumeral Muscles

Glenohumeral muscles stabilize the humerus by providing compressive forces directed into the glenoid or by resisting opposing forces from larger muscles like the deltoid. Scapula shape is correlated to rotator cuff tear likelihood and previous research found that tear-associated shapes shift the supraspinatus’ line-of-action (LOA) anteriorly, potentially inhibiting its stabilizing potential. We predicted that the tear-associated scapula shape would cause an anterior shift in all glenohumeral muscles’ LOA. We expanded previous finite element models and computational scripts to compute the stability ratios of the teres major, teres minor, infraspinatus, supraspinatus and subscapularis on tear-associated and non-tear control scapulas. We identified insertion and attachment points for each muscle and created respective straight muscle meshes in Matlab. Then, we wrapped those meshes around the scapula and humerus surfaces and simulated an arm-raising motion in the open-source modelling package, Artisynth. In Matlab, we computed the muscle LOAs and their anterior-posterior (AP) and superior-inferior (SI) stability ratios, which describe how muscles tend to pull on the humerus relative to the glenoid. We found that the mean AP stability ratios of all five glenohumeral muscles were higher in the tear-associated scapula shape compared to the control shape, indicating an anterior shift in the muscles’ LOA. Aside from the teres minor, all other muscles exhibited slightly larger SI ratios for the tear-associated scapula shape, indicating a shift superiorly in their LOA. The tear-associated scapula shape may impact certain glenohumeral muscles’ ability to stabilize the humerus, placing higher demand on posterior fibres, subscapularis and teres major to maintain anterior stability. These findings indicate a potential injury mechanism caused by scapula shape and may help to inform rotator cuff tear prevention and rehabilitation. This method can also be applied to in vivo measurements of shoulder motions and bones to provide precise, patient-specific information on rotator cuff stabilizing potential.

Ex-vivo experimental strategies for assessing unconstrained shoulder biomechanics: a scoping review protocol.

Background: Shoulder biomechanics cannot be measured directly in living persons. While different glenohumeral joint simulators have been developed to investigate the role of the glenohumeral muscles in shoulder biomechanics, a standard for these simulators has not been defined. With this scoping review we want to describe available ex-vivo experimental strategies for assessing unconstrained shoulder biomechanics. Objective: The scoping review aims at identifying methodological and/or experimental studies describing or involving ex-vivo simulators that assess unconstrained shoulder biomechanics and synthesizing their strengths and limitations. Inclusion criteria: All unconstrained glenohumeral joint simulators published in connection with ex-vivo or mechanical simulation experiments will be included. Studies on glenohumeral simulators with active components to mimic the muscles will be included. We will exclude studies where the experiment is static or the motion is induced through an external guide, e.g., a robotic device. Methods: We will perform database searching in PubMed, Embase via Elsevier and Web of Science. Two reviewers will independently assess full texts of selected abstracts. Direct backward and forward citation tracking on included articles will be conducted. We will narratively synthesize the results and derive recommendations for designing ex-vivo simulators for assessing unconstrained shoulder biomechanics.

EFFECTS OF MYOFASCIAL TRIGGER POINT RELEASE AND THERABAND STRENGTHENING AMONG THE COLLEGIATE VOLLEY BALL PLAYERS WITH GLENOHUMERAL IMPINGEMENT

Background: Volley ball is one of the common sport and most of the college students choose this as a recreational game. Almost 80% of the shoulder injuries are related to spiking movement during the game. This stress the upper arm and the shoulder leading to increased risk of injuries. The common factors that results in shoulder injuries are Glenohumeral internal rotation deficit, Glenohumeral impingement syndrome, scapular dyskinesis and altered biomechanics of ball striking movement. Aim of The Study: The present aim of the study is to identify the effectiveness of Myofascial trigger point release technique and Theraband strengthening on Glenohumeral muscles among the collegiate volley ball players with Glenohumeral impingement syndrome. Methods: There were 30 players taken for the study and pretreatment values were taken. Myofascial trigger point therapy have been applied to supraspinatus muscle. The outcome measures used for the study is Numerical pain rating scale, range of motion and shoulder pain and disability index. The post treatment values were taken. Results: The results of the present study were analyzed using pairedt test and Wilcoxon signed rank test and the test statistics shows statistically significant improvement in the posttest p value < 0.05. Conclusion: The present study concluded that Myofascial trigger point release and Theraband strengthening exercises shows significant improvement in pain reduction, improves range of motion and functional ability among the collegiate volley ball players.

Factors affecting the shoulder functional profile in elite judo athletes

ABSTRACT The aim was to investigate the effects of sex, age, preferred judo technique, dominance, and injury history on the shoulder functional status of elite judo athletes. Sixty-one elite judo athletes (38 males, age: 18.1 ± 1.2 years, body mass: 69.3 ± 13.3 kg, body height: 172.2 ± 9.8 cm, brown belt to second-degree black belt) completed three questionnaires: Western Ontario Shoulder Instability, Western Ontario Rotator Cuff, and Shoulder Instability-Return to Sport after Injury. They performed four physical tests: the glenohumeral rotator isometric strength test, upper quarter Y-balance test, unilateral seated shot put test, and modified Closed Kinetic Chain Upper Extremity Stability Test. The results showed that the female athletes had less shoulder functional abilities than the male athletes (p < 0.001 to p = 0.02). The younger athletes had poorer shoulder stability and upper extremity power than the older athletes (p < 0.001 to p = 0.02), but their glenohumeral muscles were stronger in both internal (p = 0.03) and external (p = 0.005) rotations. All the judo athletes had similar bilateral differences in shoulder functional status, except for judokas who preferred throwing techniques (p = 0.01). Injury history affected self-perceived functional status (p < 0.001), as well as upper extremity muscle capacity and neuromuscular control (p = 0.01 to p = 0.05). This study provides new insight into the shoulder functional status of elite judo athletes, which may aid in the development of sports-specific injury prevention and return-to-sport programmes to reduce the risk of shoulder injury occurrence and recurrence. Highlights Normalized levels of upper extremity abilities must be sex- and age-specific in prevention programmes. Prevention programmes may focus on muscle bilateral and anteroposterior symmetry. Prevention programmes may include psychological training tailored to the sex of judo athletes.

Ex-vivo experimental strategies for assessing unconstrained shoulder biomechanics: a scoping review protocol

Background: Shoulder biomechanics cannot be measured directly in living persons. While different glenohumeral joint simulators have been developed to investigate the role of the glenohumeral muscles in shoulder biomechanics, a standard for these simulators has not been defined. With this scoping review we want to describe available ex-vivo experimental strategies for assessing unconstrained shoulder biomechanics. Objective: The scoping review aims at identifying methodological and/or experimental studies describing or involving ex-vivo simulators that assess unconstrained shoulder biomechanics and synthesizing their strengths and limitations. Inclusion criteria: All unconstrained glenohumeral joint simulators published in connection with ex-vivo or mechanical simulation experiments will be included. Studies on glenohumeral simulators with active components to mimic the muscles will be included. We will exclude studies where the experiment is static or the motion is induced through an external guide, e.g., a robotic device. Methods: We will perform database searching in PubMed, Embase via Elsevier and Web of Science. Two reviewers will independently assess full texts of selected abstracts. Direct backward and forward citation tracking on included articles will be conducted. We will narratively synthesize the results and derive recommendations for designing ex-vivo simulators for assessing unconstrained shoulder biomechanics.

Ex-vivo experimental strategies for assessing unconstrained shoulder biomechanics: a scoping review protocol.

Background: Shoulder biomechanics cannot be measured directly in living persons. While different glenohumeral joint simulators have been developed to investigate the role of the glenohumeral muscles in shoulder biomechanics, a standard for these simulators has not been defined. With this scoping review we want to describe available ex-vivo experimental strategies for assessing unconstrained shoulder biomechanics. Objective: The scoping review aims at identifying methodological and/or experimental studies describing or involving ex-vivo simulators that assess unconstrained shoulder biomechanics and synthesizing their strengths and limitations. Inclusion criteria: All unconstrained glenohumeral joint simulators published in connection with ex-vivo or mechanical simulation experiments will be included. Studies on glenohumeral simulators with active components to mimic the muscles will be included. We will exclude studies where the experiment is static or the motion is induced through an external guide, e.g., a robotic device. Methods: We will perform database searching in PubMed, Embase via Elsevier and Web of Science. Two reviewers will independently assess full texts of selected abstracts. Direct backward and forward citation tracking on included articles will be conducted. We will narratively synthesize the results and derive recommendations for designing ex-vivo simulators for assessing unconstrained shoulder biomechanics.

Exercise-Based Muscle Development Programmes and Their Effectiveness in the Functional Recovery of Rotator Cuff Tendinopathy: A Systematic Review.

(1) Background: Rotator cuff (RC) tendinopathy causes pain and functional limitation of the shoulder. Physical exercises are effective therapies but there is no consensus on which exercise programme is the most appropriate. Objective: To analyze and compare the effectiveness of different intervention modalities-based exclusively on physical exercise muscle-development programs to improve shoulder pain and function in RC tendinopathy. (2) Methods: Systematic review (PRISMA) through a search in PubMed, WOS, PEDro, Cinahl, Scopus and Dialnet. The PEDro Scale and the Cochrane Risk of Bias analyzed the methodological quality. A pre-established table collected data on: patients, interventions, outcome measures and results. A narrative synthesis of the results was conducted. (3) Results: eight articles were selected (Cochrane: low risk of bias; PEDro: good quality). All assessed programs were effective. Only one study found statistically and clinically significant differences in favour of eccentric training. The exercises used were: eccentric/concentric/conventional, open/closed kinetic chain, with/without co-activation of glenohumeral muscle, with/without pain, and in clinic/at home. (4) Conclusions: All exercise programs were effective in RC tendinopathy, improving pain and shoulder function. No solid results were obtained when the interventions were compared due to their heterogeneity. Patients perception assessment tools were the most widely used. Amount of load applied should be considered.

Exploring the functional morphology of the Gorilla shoulder through musculoskeletal modelling.

Musculoskeletal computer models allow us to quantitatively relate morphological features to biomechanical performance. In non‐human apes, certain morphological features have long been linked to greater arm abduction potential and increased arm‐raising performance, compared to humans. Here, we present the first musculoskeletal model of a western lowland gorilla shoulder to test some of these long‐standing proposals. Estimates of moment arms and moments of the glenohumeral abductors (deltoid, supraspinatus and infraspinatus muscles) over arm abduction were conducted for the gorilla model and a previously published human shoulder model. Contrary to previous assumptions, we found that overall glenohumeral abduction potential is similar between Gorilla and Homo. However, gorillas differ by maintaining high abduction moment capacity with the arm raised above horizontal. This difference is linked to a disparity in soft tissue properties, indicating that scapular morphological features like a cranially oriented scapular spine and glenoid do not enhance the abductor function of the gorilla glenohumeral muscles. A functional enhancement due to differences in skeletal morphology was only demonstrated in the gorilla supraspinatus muscle. Contrary to earlier ideas linking a more obliquely oriented scapular spine to greater supraspinatus leverage, our results suggest that increased lateral projection of the greater tubercle of the humerus accounts for the greater biomechanical performance in Gorilla. This study enhances our understanding of the evolution of gorilla locomotion, as well as providing greater insight into the general interaction between anatomy, function and locomotor biomechanics.

The Effect of Shoulder Injury Prevention Program on Shoulder Isokinetic Strength in Young Male Volleyball Players

ABSTRACT The purpose of this study was to examine the effects of an eight-week 11 + S programme on isokinetic shoulder strength in young male volleyball players. Twenty-eight top-level young male volleyball players were recruited for this study. The players were randomly assigned into intervention (14 players) and control (14 players) groups. The intervention group performed the 11 + S as a warm-up before training at least three times a week for eight weeks. Dominant shoulder strength was measured using an isokinetic dynamometer at 60°/s and 180°/s. The functional deceleration ratio (FDR) was calculated as a functional strength profile. 20% FDR improvement after eight weeks of 11 + S at 180°/s (p = 0.003) were observed. No other statistically significant effects for shoulder strength improvement was observed (p > 0.05). Eight weeks of 11 + S warm-up programme improved the glenohumeral muscle imbalance by increasing the functional deceleration ratio (FDR) of shoulder muscles in young male volleyball players.

Mechanisms of Modulation of Automatic Scapulothoracic Muscle Contraction Timings

Erected posture provides humans a large shoulder mobility that requires complex automatic muscle synergies to accomplish joint stability needs. This is evident in shoulder abduction, wherein the voluntary activation of glenohumeral muscles is coupled with an automatic recruitment of scapulothoracic muscles. Here, we investigated whether volitional modification of the scapular position, and dynamic scapular elevation, modulate the contraction timing of five shoulder muscles (middle deltoid, upper, middle and lower fiber of the trapezius, serratus anterior) during shoulder abduction. The results show matched contraction timings of the deltoid and upper trapezius across the scapular positions, whereas the contraction timings of the middle and lower fibers of the trapezius change secondary to the scapular position. These results might reflect different central strategies to coordinate the automatic sequences of contraction of the scapulothoracic muscles. This suggest a flexible and adaptable predisposition of the motor control system in exploring alternative solutions to accomplish the functional movement needs, such as the fulfillment of unconstrained movements. Intriguingly, the shoulder abduction may represent a powerful, non-invasive, and straightforward tool to deepen the understanding of the neural basis underlying the voluntary motor command modulation of the out-of-volition automatic muscle contractions.

The Coupled Kinematics of Scapulothoracic Upward Rotation.

Scapulothoracic upward rotation (UR) is an important shoulder complex motion allowing for a larger functional work space and improved glenohumeral muscle function. However, the kinematic mechanisms producing scapulothoracic UR remain unclear, limiting the understanding of normal and abnormal shoulder movements. The objective of this study was to identify the coupling relationships through which sternoclavicular and acromioclavicular joint motions contribute to scapulothoracic UR. This was a cross-sectional observational study. Sixty participants were enrolled in this study; 30 had current shoulder pain, and 30 had no history of shoulder symptoms. Shoulder complex kinematics were quantified using single-plane fluoroscopy and 2D/3D shape matching and were described as finite helical displacements for 30-degree phases of humerothoracic elevation (30 degrees-60 degrees, 60 degrees-90 degrees, and 90 degrees-120 degrees). A coupling function was derived to estimate scapulothoracic UR from its component motions of acromioclavicular UR, sternoclavicular posterior rotation, and sternoclavicular elevation as a function of acromioclavicular internal rotation. The proportional contributions of each of the component motions were also calculated and compared between phases of humerothoracic elevation and groups. Scapulothoracic UR displacement could be effectively predicted using the derived coupling function. During the 30- to 60-degree humerothoracic elevation phase, acromioclavicular UR accounted for 84.2% of scapulothoracic UR, whereas sternoclavicular posterior rotation and elevation each accounted for < 10%. During later phases, acromioclavicular UR and sternoclavicular posterior rotation each accounted for 32% to 42%, whereas sternoclavicular elevation accounted for < 11%. Error due to the tracking of sternoclavicular posterior rotation may have resulted in an underprediction of its proportional contribution and an overprediction of the proportional contribution of acromioclavicular UR. Acromioclavicular UR and sternoclavicular posterior rotation are the predominant component motions of scapulothoracic UR. More research is needed to investigate how these coupling relationships are affected by muscle function and influenced by scapular dyskinesis.

Muscle Contributions to Upper-Extremity Movement and Work From a Musculoskeletal Model of the Human Shoulder.

Musculoskeletal models enable movement scientists to examine muscle function by computing the mechanical work done by muscles during motor tasks. To estimate muscle work accurately requires a model that is physiologically plausible. Previous models of the human shoulder have coupled scapula movement to humeral movement. While coupled movement produces a stereotypical scapulohumeral rhythm, it cannot model shrugging or independent movement of the scapula and humerus. The artificial coupling of humeral elevation to scapular rotation permits muscles that cross the glenohumeral joint, such as the rotator-cuff muscles and deltoids, to do implausible work to elevate and rotate the scapula. In reality, the motion of the scapula is controlled by thoracoscapular muscles, yet the roles of these muscles in shoulder function remains unclear. To elucidate the roles of the thoracoscapular muscles, we developed a shoulder model with an accurate scapulothoracic joint and includes scapular muscles to drive its motion. We used the model to compute the work done by the thoracoscapular muscles during shrugging and arm elevation. We found that the bulk of the work done in upper-extremity tasks is performed by the largest muscles of the shoulder: trapezius, deltoids, pectoralis major, and serratus-anterior. Trapezius and serratus anterior prove to be important synergists in performing upward-rotation of the scapula. We show that the large thoracoscapular muscles do more work than glenohumeral muscles during arm-elevation tasks. The model, experimental data and simulation results are freely available on SimTK.org to enable anyone to explore our results and to perform further studies in OpenSim 4.0.

Asymmetry in glenohumeral muscle strength of sitting volleyball players: an isokinetic profile of shoulder rotations strength.

Sitting volleyball (SV) is a popular Paralympic game, in which shoulders of SV players are overloaded continuously during play. Nevertheless, shoulder girdle muscle function has never been measured in this population yet. The objective of this study was to investigate the dominant and non-dominant strength profile of male and female elite SV players on a glenohumeral level. A total of 13 Brazilian SV national team players volunteered to participate in this study (male: N.=6, age 32.8±4.1 years, body mass 83.2±19.4 kg, seated height 1.47±0.04 m; female: N.=7, age 32.8±4.1 years, body mass 80.1±17.9 kg, seated height 1.36±0.05 m). A Biodex dynamometer was used to measure internal rotation (IR) and external rotation (ER) of the glenohumeral muscle strength at 60°/s and 180°/s velocities in a concentric/concentric mode. It was observed that male SV players were stronger than the female players at both upper limbs. Concerning the side effects, significant differences were found for IR at 60°/s velocity (F=7.55, P=0.02) and ER at 180°/s velocity (F=5.91, P=0.03), with higher values on the dominant limb in comparison to the non-dominant limb for both the male and female players. There were significant gender differences for the IR inter-limb asymmetry at 180°/s velocity, with a greater asymmetry between both shoulders in the male players compared to the female players, preference for the dominant side in both groups. The SV players have an asymmetrical rotational strength profile. As muscular imbalance is a common injury pattern among overhead players. The findings of this study may assist the SV coaches and physiotherapists for evaluation and training of strength of the ER and IR shoulders of these players.

P39 Physiotherapy management of long thoracic nerve injury (LTNI) post-flu vaccine in an immunocompromised patient with vasculitis: what is the best strategy?

Abstract Background We describe the case of a 12 year-old boy with polyarteritis nodosa presenting with long thoracic nerve injury (LTNI) post flu vaccination. Polyarteritis nodosa is an inflammatory vasculitis treated with immunosuppressive medication. Children with immunosuppression require seasonal flu vaccination, and LTNI is a recognised complication, rare in children, with no incidence documented. Physiotherapy plays a role in the conservative management of LTNI, however, there is debate regarding the most effective regime. Methods Case description with literature review of aetiology, treatment strategies and recommendations for effective therapeutic approach. Results Our patient was diagnosed with polyarteritis nodosa following an admission with intra-abdominal bleed, coeliac axis thrombosis and mesenteric artery aneurysm seen on angiogram. He responded well to steroids and immunosuppressive medication. Due to the risk of infection from immune suppression, he received seasonal intra-muscular influenza vaccination to the right deltoid. There were no initial complications, however, two weeks later, burning shoulder pain and sleep disturbance were reported. There was paraesthesia in the right hand although grip strength was not impaired. Of note, the patient is left hand-dominant. Examination revealed elevation of the right shoulder girdle and winging of the medial border of the scapula. Range of movement at the shoulder was full and pain-free. Palpation of the gleno-humeral joint line and deltoid were unremarkable. The clinical findings suggested long thoracic nerve denervation. Physiotherapy assessment demonstrated weakness in the serratus anterior muscle and abnormal scapula movement patterns, including decreased protraction. Nerve conduction studies reported decreased activation of the long thoracic nerve. Scapula recruitment exercises were advised, as well as posture correction. After a year, scapula-humeral rhythm and strength of the scapula muscles improved. Conclusion Causes of scapula-winging in children include osteochondromas, exostoses and sports-related injuries. Scapula-winging associated with LTNI is a recognised complication of flu vaccine but very rarely reported in under 16-year olds. Treatment of LTNI is poorly evidenced in the literature. However, physiotherapy including bracing to enhance proprioception, mobility exercises in supine to correct scapula position and strengthening of scapula muscles is reported. There is a lack of evidence to inform the most effective approach. The literature outlines that general gleno-humeral muscle strengthening is beneficial in improving shoulder function in LTNI. However, there is limited research investigating the specific role of scapula muscle strengthening in LTNI in children. The literature suggests that poor scapula function can impair the biomechanics of the shoulder and exercises that address scapula muscle control can improve movement patterns. The time to recovery from LTNI is estimated between 1-2 years and maintaining muscle bulk is our challenge, as the nerve recovers. Clinicians need to be aware of LTNI complicating flu vaccine in immuno-compromised children. We highlight the importance of physiotherapy in improving scapula biomechanics. Conflicts of Interest The authors declare no conflicts of interest.

Sex differences in glenohumeral muscle activation and coactivation during a box lifting task

Manual material handling is associated with shoulder musculoskeletal disorders, especially for women. Sex differences in glenohumeral muscle activity may contribute to women’s higher injury risk by affecting shoulder load and stability. We assessed the effects of sex (25 women vs 26 men) and lifting load (6 kg vs 12 kg) on muscle activation during box lifting from hip to eye level. Surface and intramuscular electromyography were recorded from 10 glenohumeral muscles. Most muscles were more activated for the heavier box and for women. These effects were larger for ‘prime movers’ than for stabilisers and antagonists. Despite their apparently heterogeneous effects on muscle activity, sex and mass did not affect Muscle Focus, a metric of coactivation. This may be partly related to the limited sensitivity of the Muscle Focus. Nevertheless, sex differences in strength, more than in coactivation patterns, may contribute to the sex imbalance in the prevalence of musculoskeletal disorders. Practitioner summary: We studied sex differences in glenohumeral muscle activity in a lifting task to eye level. Women lifting a 6-kg box activated their muscles similarly to men lifting a 12-kg box, i.e. up to 48% of their maximum capacity. Interventions minimising shoulder load should be implemented, especially for women. Abbreviations: BB: biceps brachii; DeltA: anterior deltoid; DeltL: lateral deltoid; DeltP: posterior deltoid; DoF: degrees of freedom; ED: effect duration; EMG: electromyography; ES: effect size; Infra: infraspinatus; Lat: latissimus dorsi; MF: muscle focus; MMH: manual material handling; MVA: maximal voluntary activation; Pect: pectoralis major; Subscap: subscapularis; Supra: supraspinatus; TB: triceps brachii

Volitional Preemptive Abdominal Contraction and Upper Extremity Muscle Latencies During D1 Flexion and Scaption Shoulder Exercises.

The abdominal-bracing maneuver, a volitional preemptive abdominal contraction (VPAC) strategy, is commonly used during resisted shoulder exercises. How VPAC affects shoulder-muscle function during resisted shoulder exercise is unknown. To identify the effects of VPAC on selected parascapular and glenohumeral muscles during specific shoulder exercises with or without resistance. Cross-sectional study. Clinical biomechanics research laboratory. Twenty-two asymptomatic volunteers between 18 and 40 years of age. Participants performed arm elevation in scaption and D1 shoulder-flexion (D1F) patterns with and without resistance and VPAC. Electromyography was used to test the muscle-contraction amplitudes and onset timing of the anterior deltoid, posterior deltoid, upper trapezius, lower trapezius, and serratus anterior. Muscle-response amplitudes were quantified using root mean square electromyography. Shoulder-muscle relative-onset timing was quantified in reference to kinematic elbow-movement initiation. The VPAC increased serratus anterior amplitude during D1F ( P < .001) and scaption ( P < .001) and upper trapezius amplitude ( P < .001) in scaption. All muscle amplitudes increased with resistance. The VPAC decreased muscle-onset latencies for the anterior deltoid ( P < .001), posterior deltoid ( P = .008), upper trapezius ( P = .001), lower trapezius ( P = .006), and serratus anterior ( P = .001) during D1F. In addition, the VPAC decreased muscle-onset latencies for the anterior deltoid ( P < .001), posterior deltoid ( P = .007), upper trapezius ( P < .001), lower trapezius ( P < .001), and serratus anterior ( P < .001) during scaption. The VPAC affected only the parascapular muscles that had the greatest scapular-stabilizing roles during the specific open chain movement we tested. It decreased latencies in all muscles. These neuromuscular changes may enhance the stability of the shoulder during D1F and scaption exercises.

Spatial dependency of shoulder muscle demand during dynamic unimanual and bimanual pushing and pulling

Work involving extensive pushing and pulling is associated with higher frequency of shoulder complaints. While reports of shoulder muscle demand during submaximal isometric tasks are abundant, dynamic submaximal push-pull exertions are not well understood. We evaluated how muscle demand (weighted EMG average) of surface glenohumeral muscles varies with task type and target. Seventeen healthy young adults performed seated unimanual and bimanual pushes and pulls to 3 thoracohumeral elevations (20°, 90°, 170°) and 4 elevation planes (0°, 45°, 90°, 135°) with loading at 15% of isometric push-pull capacity. Pulling required less demand than pushing (p < 0.0001). Muscle demand varied more with elevation than elevation plane. The lowest target had highest demand for pulling (p < 0.01), and the most elevated target had highest demand for pushing (p < 0.0001). Working above the shoulder is known to increase demand during isometric tasks, however, these results suggest that for dynamic tasks working against gravity has a larger effect on demand than task target.

The Comparison of Electromyographic Activity of Selected Shoulder Girdle Muscles in Elite Table Tennis Players with and without Shoulder Impingement Syndrome during Forehand Topspin

Introduction: Shoulder injuries are very common in sports such as table tennis in which the athletes’ upper limb operates higher than shoulder level. On the other hand, weak or inappropriate shoulder muscle activity can be related to incidence of an injury. The purpose of this study was to compare the activation of selected scapulohumeral muscles in table tennis athletes between healthy and shoulder impingement syndrome group during a strike of forehand topspin. Materials and Methods: Thirty national-level male table tennis players aged 20 to 28 years were selected purposefully and divided into shoulder impingement syndrome (n = 15), and healthy (n = 15) groups. The surface electromyographic activity of selected muscles from scapulothoracic and glenohumeral joints was recorded during the strike of forehand topspin . Results: The level of the activity of the serratus anterior muscle (P = 0.007) and supraspinatus muscle (P = 0.001) in the shoulder impingement syndrome group was significantly lower and the level of upper trapezius muscle activation in the shoulder impingement syndrome subjects was significantly higher (P = 0.009) in shoulder impingement syndrome group compared to the healthy group. However, no significant differences were observed in the activation level of lower trapezius (P = 0.301), anterior deltoid (P = 0.314), and biceps brachii (P = 0.291) muscles. Conclusion: The results of this study showed that patients with impingement syndrome demonstrated unnatural and changed levels of muscle activity in scapulohumeral articulation during the forehand topspin strike. The findings confirm the theories that shoulder impingement may be related to changes in the activity level of scapulothoracic and glenohumeral muscles.

National Athletic Trainers' Association Position Statement: Evaluation, Management, and Outcomes of and Return-to- Play Criteria for Overhead Athletes With Superior Labral Anterior-Posterior Injuries.

To present recommendations for the diagnosis, management, outcomes, and return to play of athletes with superior labral anterior-posterior (SLAP) injuries. In overhead athletes, SLAP tears are common as either acute or chronic injuries. The clinical guidelines presented here were developed based on a systematic review of the current evidence and the consensus of the writing panel. Clinicians can use these guidelines to inform decision making regarding the diagnosis, acute and long-term conservative and surgical treatment, and expected outcomes of and return-to-play guidelines for athletes with SLAP injuries. Physical examination tests may aid diagnosis; 6 tests are recommended for confirming and 1 test is recommended for ruling out a SLAP lesion. Combinations of tests may be helpful to diagnose SLAP lesions. Clinical trials directly comparing outcomes between surgical and nonoperative management are absent; however, in cohort trials, the reports of function and return-to-sport outcomes are similar for each management approach. Nonoperative management that includes rehabilitation, nonsteroidal anti-inflammatory drugs, and corticosteroid injections is recommended as the first line of treatment. Rehabilitation should address deficits in shoulder internal rotation, total arc of motion, and horizontal-adduction motion, as well as periscapular and glenohumeral muscle strength, endurance, and neuromuscular control. Most researchers have examined the outcomes of surgical management and found high levels of satisfaction and return of shoulder function, but the ability to return to sport varied widely, with 20% to 94% of patients returning to their sport after surgical or nonoperative management. On average, 55% of athletes returned to full participation in prior sports, but overhead athletes had a lower average return of 45%. Additional work is needed to define the criteria for diagnosing and guiding clinical decision making to optimize outcomes and return to play.

A descriptive analysis of shoulder muscle activities during individual stages of the Turkish Get-Up exercise

The Turkish Get-Up (TGU) is a complex and multi-planar exercise; the performer begins in a supine lying position, progresses toward upright standing through a series of 7 stages while holding a mass overhead in one hand, and returns to the original supine lying position through a reversal of the same 7 stages. A descriptive analysis of shoulder muscle activity during the TGU may provide insight toward its use in training and rehabilitation contexts. Our objectives were to: (1) describe the activity patterns from a subset of muscles that span the glenohumeral joint during individual stages of the TGU, and (2) interpret these patterns through comparisons between left- and right-side muscles, and between the up and down phases of the TGU. Twelve individuals with at least one-year experience performing the TGU were included in this study. Surface electromyographic (EMG) recordings were bilaterally obtained from 8 glenohumeral muscle groups while participants performed ten trials of the TGU with a kettlebell in their right hand. Instants representing the start and end of each TGU stage were identified from a synchronized video for each trial, and EMG activities for each muscle were integrated over the duration of each stage. Average integrated EMG and within-participant coefficients of variation were calculated. Overall, the greatest muscular demand occurred during the second (press to elbow support) and fifth (leg sweep) stages. Activities from muscles on the ipsilateral side to the kettlebell (right-side) were greater during stages when the contralateral upper limb did not contribute to supporting the body; however, contralateral (left-side) muscles were invoked during stages when the non-kettlebell-bearing forearm or hand contributed to supporting the body. The results suggest the importance of training both phases of the TGU to gain the most benefit from the exercise and highlights the asymmetric nature of the exercise, which may be particularly relevant for athletes engaged in activities with rotational demands.