Electromyographic activity of selected shoulder muscles in commonly used therapeutic exercises

The Effects of Body Positions and Abduction Angles on Shoulder Muscle Activity Patterns during External Rotation Exercises

BACKGROUND

Excess and repetitive glenohumeral external rotation (ER) is at a higher risk for shoulder injuries, which occurs frequently in professional sports and specific occupations. Current rehabilitation programs emphasize selective targeting of muscle activity, which can help restore dysfunctional muscle imbalances or prevent injuries. However, the impact of different body postures on GH muscle activity during ER exercises has not been fully understood. Therefore, the purpose of this study was to investigate shoulder EMG activity for different body positions and humeral abduction angles during ER exercises.

METHOD

Twenty-three healthy young men (age: 22.3 ± 2.3, height: 175.75 ± 4.02, mass: 75.37 ± 9.14) participated in this study. Surface Electromyography was recorded from seven shoulder muscles: upper trapezius, lower trapezius, serratus anterior, infraspinatus, and deltoid. Six ER exercises: three postures (sitting, supine lying, and prone lying) and two abduction angles (ABD; 45° and 90°) were tested using an isokinetic dynamometer.

RESULTS

During a sitting position, the lower trapezius/upper trapezius muscle activity ratios were significantly increased for sitting compared to supine lying and prone lying (p < 0.001, p = 0.004). Serratus anterior/upper trapezius co-contraction indices were significantly increased for 90° than 45° ABD (p < 0.001).

CONCLUSION

These findings can provide insight into new training programs aimed at restoring GH muscle imbalances.

Effects of Exercise Intervention (with and without Joint Mobilization) in Patients with Adhesive Capsulitis: A Systematic Review and Meta-Analysis

This review aimed to investigate the effects of exercise and exercise with joint mobilization on shoulder range of motion (ROM) and subjective symptom recovery in patients with adhesive capsulitis (AC). Related Studies published from 2000 to 2021 that were peer-reviewed and for which pre-and post-values could be calculated were extracted from PubMed, CINAHL, SPORTDiscus, and Web of Science. Nine studies met our inclusion criteria. As a result of calculating the standard mean difference (SMD) and 95% confidence intervals (CI), both exercise and exercise with joint mobilization showed a large effect on shoulder ROM and subjective outcomes. The combination showed a more significant effect than exercise alone on shoulder flexion (SMD = -1.59 [-2.34, -0.65]), extension (SMD = -1.47 [-2.05, -0.89]), internal rotation (SMD = -1.77 [-2.17, -1.36], external rotation (SMD = -2.18 [-2.92, -1.44]), and abduction ROM (SMD = -1.99 [CI -3.86, -0.12]). Patients who performed exercise alone showed a higher effect of improvement in subjective function (SMD = 3.15 [2.06, 4.24]) and pain (SMD = 4.13 [1.86, 6.41]). Based on these results, an AC rehabilitation exercise program should be developed by adjusting the amount of exercise and joint mobilization by identifying the patient's needs, subjective symptoms, and ROM.

Co-creation of an exercise inventory to improve scapular stabilization and control among individuals with rotator cuff-related shoulder pain: a survey-based study amongst physiotherapists

Background

Scapular stabilization exercises (SSE) are often included in the treatment of individuals with rotator cuff-related shoulder pain (RCRSP) to decrease pain and improve function. These SSE typically aim to strengthen the scapular muscles and optimize dynamic neuromuscular control of the scapula, which may improve overall shoulder stability and movement quality. No consensus of the recommended SSE for the management of RCRSP is available. Hence, this study aimed to consult physiotherapists to co-create an inventory of recommended SSE based on the exercise’s relevance and frequency of prescriptions for the rehabilitation of individuals with RCRSP.

Methods

A group of 16 physiotherapists with experience in treating shoulder pain participated in a sequential consultation incorporating two distinct rounds of consultation focusing on SSE (modified Delphi design). In round 1, physiotherapists identified and demonstrated up to 10 SSE that they commonly recommend or use among individuals with RCRSP. The description and performance of all SSE were audio and video recorded. All SSE suggested by more than one participant in round 1 advanced to round 2. In round 2, physiotherapists rated these SSE on a 4-point Likert scale according to their perceived relevance and frequency of prescription for this population.

Results

In round 1, out of the 25 SSE recommended by participants, 19 SSE (76.0%) were recommended by more than one physiotherapist and advanced to round 2. In round 2, 13 SSE were consensually classified (agreement ≥75%) as being relevant for the rehabilitation of individuals with RCRSP. SSE targeting the recruitment of the serratus anterior and lower trapezius muscles were considered the most relevant for the management of RCRSP, whereas SSE targeting neuromuscular scapular control were the most prescribed SSE for the management of RCRSP.

Conclusions

An inventory composed of 13 SSE was co-created by physiotherapists based on their relevance and frequency of prescription for the rehabilitation of individuals with RCRSP. When designing an exercise program, physiotherapists can use this SSE inventory to inform their exercise selection, in combination with their current knowledge on shoulder rehabilitation, as well as patients’ preferences.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40945-022-00132-7.

Band Pull-Apart Exercise: Effects of Movement Direction and Hand Position on Shoulder Muscle Activity

Background/Purpose

The Elastic band pull-apart exercise is commonly used in rehabilitation. It involves pulling an elastic resistance band with both hands in horizontal abduction or diagonal arm movements. The extent of muscle activation during this exercise is unknown. The purpose of this study was to measure the electromyographic (EMG) activity of shoulder-girdle muscles during the pull-apart exercise using resistance bands and to determine the effects of arm position and movement direction on shoulder-girdle muscle activity.

Materials/Methods

Surface EMG activity was measured on the infraspinatus, upper trapezius, middle trapezius, lower trapezius and posterior deltoid of the dominant shoulder. After measurement of maximal voluntary contraction (MVC) for each muscle, subjects performed the band pull-apart exercise in three hand positions (palm up, neutral, palm down) and three movement directions (diagonal up, horizontal, diagonal down). Elastic band resistance was chosen to elicit moderate exertion (5/10 on the Borg CR10 scale). The order of the exercises was randomized and three repetitions of each exercise were performed. Mean peak EMG activity in each muscle across the repetitions was calculated and expressed as a percentage of MVC. Peak normalized EMG activity in each muscle was compared in two-way (hand position x direction) repeated-measures ANOVA.

Results

Data were collected from 10 healthy subjects (all males, age 36±12 years). Peak muscle activity ranged from 15.3% to 72.6% of MVC across muscles and exercise conditions. There was a significant main effect of hand position for the infraspinatus and lower trapezius, where muscle activity was highest with the palm up hand position (p < 0.001), and for the upper trapezius and posterior deltoid, where muscle activity was highest with the palm down position (p-value range < 0.001-0.004). There was a significant main effect of movement direction, where the diagonal up direction demonstrated the highest muscle activity for the infraspinatus, upper trapezius, lower trapezius, and posterior deltoid (p-value range < 0.001-0.02).

Conclusion

Altering hand position and movement direction during performance of an elastic band pull-apart exercise can affect magnitudes of shoulder-girdle muscle activity. Clinicians may alter a patient's hand position and movement direction while performing the band pull-apart exercise in order to increase muscle activity in target muscles or diminish muscle activity in other muscles.

Level of Evidence

2b.

Comparison of the Shoulder External Rotator Strength and Asymmetry Ratio Between Workers With and Without Shoulder Impingement Syndrome

Kim, J-H, Kwon, O-Y, Hwang, U-J, Jung, S-H, Ahn, S-H, and Kim, H-A. Comparison of shoulder external rotator strength and the asymmetry ratio between workers with and without shoulder impingement syndrome. J Strength Cond Res 35(12): 3364-3369, 2021-Shoulder impingement syndrome (SIS) is the most common shoulder problem causing shoulder pain. Several studies have indicated that shoulder external rotator muscles provide dynamic stability to the shoulder joint. However, the relationship of SIS to changes in shoulder external rotator muscle strength remains controversial. The purpose of the study was to compare the shoulder external rotator strength and asymmetry ratio between workers with SIS and the normal group in a side-lying position. Twelve male industrial workers with SIS and the normal group of 12 workers participated in this study. A pulling sensor measured shoulder external rotator muscle strength in a side-lying position with the shoulder at 0° and 90° of flexion. The asymmetry ratio was calculated by a specific formula using the shoulder external rotator muscle strength of the dominant side and the unaffected side. Two-way analysis of variance was used to determine between-group differences in shoulder external rotator muscle strength and the asymmetry ratio among the 2 positions. Subjects with SIS did not exhibit significant differences in shoulder external rotator muscle strength in the side-lying position with the shoulder at 0° and 90° of flexion relative to the normal group. However, subjects with SIS had a significantly increased asymmetry ratio of shoulder external rotation strength in the side-lying position with the shoulder at 90° of flexion compared with the normal group. In conclusion, workers with SIS had an asymmetry of shoulder external rotator strength in side-lying with the shoulder at 90° of flexion.

Strategies for controlling axial shoulder rotation change shoulder muscle activity during external rotation exercises

BACKGROUND

The infraspinatus muscle has a crucial role in shoulder stability. Although axial shoulder rotation is useful for selective activation of the infraspinatus, no study has examined the influence of exercise position on axial shoulder rotation during shoulder external rotation (ER) exercises. Thus, this study investigated the muscle activity in the infraspinatus, posterior deltoid, and middle trapezius during shoulder ER exercises performed with and without controlled axial shoulder rotation in 2 different positions.

METHODS

Twenty healthy subjects performed prone external rotation (PER) exercises with and without pressure biofeedback and seated external rotation (SITER) exercises with and without posterior humeral head gliding. Muscle activity during each ER exercise was measured using surface electromyography.

RESULTS

Exercise strategy (P < .001) and position (P < .001) had a significant main effect on muscle activity in the infraspinatus and posterior deltoid. However, no significant interaction between strategy and position was observed. For muscle activity in the middle trapezius, strategy and position had a significant interaction effect (P = .014). Muscle activity in the infraspinatus increased significantly with the use of strategies to control axial shoulder rotation, whereas muscle activity in the posterior deltoid and middle trapezius decreased significantly. For all 3 muscles, greater activity was observed in the prone position than the seated position.

CONCLUSION

We suggest that PER with pressure biofeedback can be useful to improve selective activation of the infraspinatus muscle while further eliciting infraspinatus muscle activity.

Anterior cruciate ligament reconstruction with the use of adductor canal block can achieve similar pain control as femoral nerve block

PURPOSE

Moderate-to-severe postoperative pain remains a challenge for both patients and surgeons after anterior cruciate ligament reconstruction (ACLR). The purpose of this study was to systematically review the current evidence in the literature to compare adductor canal block (ACB) with femoral nerve block (FNB) in the treatment of ACLR.

METHODS

A comprehensive search of the published literature in PubMed, Scopus, EMBASE, and Cochrane Library databases was performed. Only English randomized clinical trials (RCTs) were included in this study. The primary outcome was pain score. Secondary outcome measures included opioid consumption, postoperative adverse events, patient satisfaction, and quadriceps strength.

RESULTS

Eight RCTs with a total of 587 patients were included. No statistically significant difference was observed between the ACB and FNB groups in pain scores at 6 h, 12 h, 24 h, or 48 h; cumulative opioid consumption at 24 h or 48 h; patient satisfaction at 24 or 48 h; and postoperative adverse event. However, ACB showed superior quadriceps strength in the early postoperative period.

CONCLUSIONS

Both treatments provided similar overall pain relief after ACLR. The potential benefits of quadriceps preservation with ACB are worthy of future study. Therefore, ACB is recommended as an attractive alternative to FNB as the peripheral nerve block of choice for ACLR.

LEVEL OF EVIDENCE

Meta-analysis of Level 1 was performed in this study.

The Relationship Between Surface Electromyographic Activity and Torque Production of the Infraspinatus Muscle in Shoulder Rehabilitation Exercises

In current rehabilitation practice, exercise selection is commonly based on the amount of muscle recruitment demonstrated by electromyographic (EMG) analysis. A preponderance of evidence supports the concept that EMG of a muscle and torque output are positively correlated. This study was designed to investigate the relationship between surface EMG activity of the infraspinatus and torque production during exercises involving shoulder external rotation (ER). A total of 30 participants (average age = 24.6 y) performed maximum voluntary isometric contraction of ER at 5 points within the range of motion of 3 shoulder exercise positions with concomitant surface EMG recording. As a maximal internally rotated position was approached, maximum ER torque and minimum or near-minimum EMG recruitment were demonstrated. Conversely, at maximally externally rotated positions, EMG activity was greatest and torque values were lowest. An inverse relationship between joint torque output and EMG activity was established in each of the 3 exercises. The inverse relationship between EMG activity and torque output during Shoulder ER suggests that there may be additional factors warranting consideration during exercise selection. Further research may be needed to determine the relative value of electrical activity versus torque output to optimize the selection of rehabilitative exercises.

How Has Electromyography Been Used to Assess Reaching in Infants? A Systematic Review

The aims of this systematic review were: to investigate the use of surface electromyography in the assessment of reaching in infants; to assess the usefulness of this tool to the assessment of reaching, and its parameters and limitations; to assess the methodological quality of the studies available in the literature. The search in the databases MEDLINE, SciELO, LILACS, Embase, PEDro, Cochrane, and EBSCO resulted in 5 selected studies. The studies aimed to elucidate how muscle behavior occurs in the development of reaching. The lack of standardized recommendations for the use of EMG in infants limit the reproducibility and comparison between studies. There are challenges and limitations regarding the use of electromyography in infants, which are caused by peculiarities inherent to the development of the neuromotor and musculoskeletal systems.

Adductor Canal Nerve Versus Femoral Nerve Blockade for Pain Control and Quadriceps Function Following Anterior Cruciate Ligament Reconstruction With Patellar Tendon Autograft: A Prospective Randomized Trial

PURPOSE

To compare femoral nerve blockade (FNB) versus adductor canal nerve blockade (ACB) for postoperative pain control and quadriceps muscle function in patients undergoing anterior cruciate ligament (ACL) reconstruction with patellar tendon autograft.

METHODS

A randomized therapeutic trial of 90 patients undergoing ACL reconstruction with patellar tendon autograft was conducted comparing ACB versus FNB at 24 hours, 2 and 4 weeks, and 6 months postsurgery. Early outcome measures included average pain score and morphine equivalent units (milligrams) consumed, quadriceps surface electromyography, straight leg raise, and ability to ambulate without assistive devices. The 6-month outcome measures included knee range of motion (ROM), isokinetic knee extension peak torque, single-leg squat, and single-leg hop performance. Complications were recorded throughout the study for the development of anterior knee pain, knee extension ROM loss, deep vein thrombosis, and graft failure. Mixed-model analysis of variance and Mann-Whitney U tests were performed using an alpha of .05.

RESULTS

Quadriceps surface electromyography deficits were higher for FNB at 24 hours (P < .001) and 2 weeks (P < .001) when compared with the ACB group. There were no between-groups difference for subjective pain (P = .793) or morphine consumption (P = .358) within the first 24 hours of surgery. A higher percentage of patients in the ACB group met the full ambulation criteria at 4 weeks compared with the FNB group (100% vs 84.2%, P < .001). No between-group differences were observed at 6 months; however, the rate of knee extension ROM loss was higher for the FNB group versus the ACB group (21.1% vs 5.0%, P = .026), respectively.

CONCLUSIONS

ACB was as effective as FNB at providing pain control while eliciting fewer quadriceps muscle activation deficits and fewer postoperative complications. Based on previous evidence and the results of this study, we recommend the use of ACB over FNB for the analgesic management of patients undergoing ACL reconstruction with patellar tendon autograft.

LEVEL OF EVIDENCE

Level I, prospective randomized controlled trial.

Effects of 3 Infraspinatus Muscle Strengthening Exercises on Isokinetic Peak Torque and Muscle Activity

CONTEXT

The infraspinatus muscle plays a particularly important role in producing primary external rotation (ER) torque and dynamic stability of the shoulder joint. Previous studies have reported that prone external rotation with horizontal abduction (PER), side-lying wiper exercise (SWE), and standing external rotation (STER) were effective exercises for strengthening the infraspinatus. However, we do not have enough knowledge about changes in muscle strength and dynamic muscle activity in each exercise under dynamic conditions.

OBJECTIVE

To compare the ER muscle strength, muscle activity among exercise methods and between muscle contraction types during 3 different exercises.

DESIGN

Repeated measures design in which ER muscle strength and muscle activities data were collected from subjects under 3 exercise conditions.

SETTING

Outpatient clinic.

PARTICIPANTS

A total of 15 healthy men with no shoulder, neck, or upper-extremity pain were participated.

INTERVENTION

The subjects performed 3 different exercises randomly in concentric and eccentric using a Biodex dynamometer at an angular velocity of 60°/s.

MAIN OUTCOME MEASURES

The ER peak torque (PT) data was collected and surface electromyography was used to measure the activity of the infraspinatus and posterior deltoid muscles and infraspinatus to posterior deltoid muscle activity ratio.

RESULTS

There was significant main effect for muscle contraction type in ER PT (P < .05). The concentric PT was greater during PER (P < .05) and SWE (P < .05) compared with eccentric. The main effect for exercise was found in ER PT and muscle activity (P < .05). The ER PT and infraspinatus muscle activity were the largest increased during PER whereas the lowest during STER in both concentric and eccentric (P < .05).

CONCLUSION

The results of this study suggest that PER is an exercise for strengthening the infraspinatus muscle effectively.

Electromyographic analysis of infraspinatus and scapular muscles during external shoulder rotation with different weight loads and positions

BACKGROUND

Strengthening the infraspinatus is important in shoulder rehabilitation. Changes in infraspinatus activity with changing load and position have not been quantified. We sought to determine the most appropriate load and posture for early infraspinatus strengthening by assessing for changes in electromyographic activity in the healthy infraspinatus and other shoulder girdle muscles during isometric external rotational exercise under different loads with the shoulder adducted in the supine and seated positions.

METHODS

Sixteen healthy adults (30 shoulders) performed isometric shoulder external rotation in the sitting and supine positions, starting with the shoulder and forearm in neutral position and the elbow flexed 90°. Loads (0.5 kg, 1 kg, and 2 kg) were applied at rest. We assessed the infraspinatus, upper trapezius, posterior deltoid, and biceps brachii. For analysis, we used the mean percentage of maximum voluntary muscle contraction (%MVC) value measured during each isometric contraction divided by the maximum voluntary muscle contraction (MVC) of each muscle.

RESULTS

In the infraspinatus and posterior deltoid, significant interaction was observed between body position and load. Compared to the sitting position, an increase in activity in the supine position was attenuated as load increased, especially at 2 kg. The supine values of the upper trapezius and biceps brachii were always significantly lower than those in the sitting position regardless of load.

CONCLUSION

The activity of the infraspinatus can be increased gradually during rehabilitation by beginning in the supine position, which assures low activity of the upper trapezius and biceps brachii. Exercise with the shoulder adducted in the supine position can strengthen the infraspinatus gradually and avoid compensatory mobility.

LEVEL OF EVIDENCE

Level 3.

Infraspinatus Isolation During External Rotation Exercise at Varying Degrees of Abduction

CONTEXT

External rotation (ER) strengthening exercises are a common component of shoulder injury prevention and rehabilitation programs. They are primarily intended to target the infraspinatus muscle, based on its role in glenohumeral stabilization and inferior humeral glide. ER also recruits the posterior deltoid, which can be undesirable due to its role in subacromial space narrowing.

OBJECTIVE

To determine the angle of humeral abduction that maximizes the infraspinatus to posterior deltoid activation ratio (INFRA/PD) during ER.

DESIGN

Within-subjects repeated-measures controlled lab trial.

PARTICIPANTS

A total of 10 healthy participants (5 males, 5 females) aged 21 (0.67) years participated in the study.

INTERVENTION

7 consecutive repetitions of ER at 7 different abduction angles ranging from 0° to 90°, with resistance normalized to 3% body mass.

MAIN OUTCOME MEASURES

Surface electromyography was performed on the infraspinatus, middle deltoid, and posterior deltoid. Surface electromyography data were processed to determine absolute muscle activation as well as INFRA/PD at each abduction angle. Group means were compared between abduction angles using 1-way analysis of variance.

RESULTS

Abduction significantly reduced overall infraspinatus activity but increased posterior deltoid activity (P < .01). Average and peak INFRA/PD decreased as the angle of abduction increased (P < .001 and P < .01, respectively).

CONCLUSION

Our findings suggest that ER should be performed in 0° of abduction to maximize infraspinatus isolation. Slight abduction, such as placing a towel under the humerus, as recommended by some clinicians, may improve patient comfort, but did not increase infraspinatus isolation in this study.

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.

Neuromuscular adaptations in shoulder function and dysfunction

Neuromuscular activity, organized in coordinated patterns, forms the basis of task-specific function in sports and exercise. The content and extent of these patterns may be variable, but include elements of activation/inhibition, co-activation, concentric/eccentric activation, proximal-to-distal activation, plyometric activation, and preactivation stiffness. They may be based on inherent neuromuscular architecture, but are commonly affected by positive or negative adaptations to imposed functional demands. Positive neuromuscular adaptations improve the efficiency of performing the task, which can result in less energy expenditure, maximum force delivered to the task, and protection of involved joints from excessive loads/motions, and improve the effectiveness of task performance. They frequently result from specific training in task mechanics and optimal conditioning of the neuromuscular structures involved in the task. Negative neuromuscular maladaptations can affect the efficiency of performing the task, increase energy expenditure and loads, decrease the effectiveness of task performance, and can be associated with clinical presentation of injury symptoms. They can result from overload, injury, and/or limited recovery. This chapter will focus specifically on shoulder joint function to provide examples of positive adaptations and negative maladaptations. It will then provide guidelines for clinical evaluation, treatment of clinical injury, and training/conditioning, based on understanding the neuromuscular activation.

Isometric muscle activation of the serratus anterior and trapezius muscles varies by arm position: a pilot study with healthy volunteers with implications for rehabilitation

BACKGROUND

This study aimed to determine the most appropriate angle and moving direction of the arm for improving coordination of the periscapular muscles, including the serratus anterior (SA), upper trapezius (UT), middle trapezius (MT), and lower trapezius (LT).

METHODS

Muscle activation amplitudes were evaluated in the SA, UT, MT, and LT in 11 healthy subjects by use of surface electromyography. The subjects were asked to maintain the arm position at 5 elevated positions with maximal effort against applied manual forces, which were directed from upper to lower (test 1), lower to upper (test 2), posterior to anterior in the frontal plane and lateral to medial in the sagittal plane (test 3), and anterior to posterior in the frontal plane and medial to lateral in the sagittal plane (test 4). The relative activity of the UT with respect to the SA, MT, and LT was calculated, resulting in the UT/SA, UT/MT, and UT/LT ratios.

RESULTS

Test 4 in all positions but 150° of elevation in the frontal plane showed high activity of the SA with a low UT/SA ratio. High MT activity with a low UT/MT ratio was observed during test 3 at the 90° elevated position, whereas high LT activity without UT hyperactivation was not found.

DISCUSSION

To strengthen the periscapular muscles in the balanced condition, horizontal adduction is recommended for the SA. Horizontal abduction at the 90° elevated position should be effective for the MT. Because no technique in this study was effective for the LT, further studies are needed.

Shoulder muscle activity during the modified dynamic relocation test and side-lying shoulder external rotation: a cross-sectional study on asymptomatic individuals

OBJECTIVES

(1) to compare activity levels between monitored muscles during the dynamic relocation test (DRT); (2) to assess changes in muscle activation variability over 10 trials; (3) to assess within-muscle difference activity levels between the DRT and the unloaded side-lying shoulder external rotation exercise.

METHODS

This is a cross-sectional, laboratory-based, repeated measures study. Thirty asymptomatic individuals performed the DRT and unloaded side-lying external rotation. The order of exercises was randomized. Superficial electromyography was used for recording the supraspinatus, infraspinatus, middle deltoid, posterior deltoid, pectoralis major, and latissimus dorsi muscles. The main outcome measures were mean muscle activity, expressed as % of maximal isometric voluntary contraction.

RESULTS

We found significant between-muscles differences in activity (F_t = 14.11, p < 0.001) during the DRT. Post hoc analysis suggested between-trial variability did not change over the 10 trials, (F = 18.2, p < 0.001). Within-muscle comparisons between the DRT and side-lying shoulder external rotation suggested significant differences between these exercises (F = 32.37, p < 0.001).

CONCLUSIONS

considering the monitored muscles, supraspinatus, infraspinatus, pectoralis major, and latissimus dorsi are the main muscles contracting during the DRT. Of all monitored muscles, supraspinatus muscle was the only one presenting higher activity levels during the DRT when compared to the unloaded side-lying shoulder external rotation.

The American Society of Shoulder and Elbow Therapists' consensus statement on rehabilitation following arthroscopic rotator cuff repair

This is a consensus statement on rehabilitation developed by the American Society of Shoulder and Elbow Therapists. The purpose of this statement is to aid clinical decision making during the rehabilitation of patients after arthroscopic rotator cuff repair. The overarching philosophy of rehabilitation is centered on the principle of the gradual application of controlled stresses to the healing rotator cuff repair with consideration of rotator cuff tear size, tissue quality, and patient variables. This statement describes a rehabilitation framework that includes a 2-week period of strict immobilization and a staged introduction of protected, passive range of motion during weeks 2-6 postoperatively, followed by restoration of active range of motion, and then progressive strengthening beginning at postoperative week 12. When appropriate, rehabilitation continues with a functional progression for return to athletic or demanding work activities. This document represents the first consensus rehabilitation statement developed by a multidisciplinary society of international rehabilitation professionals specifically for the postoperative care of patients after arthroscopic rotator cuff repair.

The influence of various resistance loads on the ratio of activity of the external rotator muscles of the shoulder and the anterior gliding of the humeral head during external rotation exercise

[Purpose] To quantify the ratio of activation of the infraspinatus and posterior deltoid muscles and the anterior gliding motion of the humeral head during external rotation (ER) motions of the shoulder performed in prone position against different external resistance loads. [Subjects] Twenty healthy women between the ages of 20 and 30 years. [Methods] Activity ratio was quantified as the difference in the root mean square of the smoothed electromyography signal (EMG) of the posterior deltoid to the infraspinatus muscle, and anterior gliding pressure of the humeral head using a pressure biofeedback unit (PBU), for three resistance loads: 0, 1 and 2 kg. [Results] There was a significant correlation among all three variables (load, ratio, and pressure). Anterior gliding pressure correlated with the activity ratio, with activity of the posterior deltoid increasing with the magnitude of the resistance load. [Conclusion] There was a positive association between the magnitude of resistance load, activity of the posterior deltoid and anterior gliding pressure of the humeral head. The PBU could be used to facilitate the recruitment of the infraspinatus muscle at higher loads to improve glenohumeral joint stability during ER exercise against higher resistance.

Electromyographic Analysis of the Shoulder Girdle Musculature During External Rotation Exercises

Background:

Implementation of overhead activity, a key component of many professional sports, requires an effective and balanced activation of the shoulder girdle muscles, particularly during forceful external rotation (ER) motions.

Purpose:

To identify activation strategies of 16 shoulder girdle muscles/muscle segments during common shoulder ER exercises.

Study Design:

Descriptive laboratory study.

Method:

Thirty healthy subjects were included in this study, and 16 shoulder girdle muscles/muscle segments were investigated (surface electrode: anterior, middle, and posterior deltoid; upper, middle, and lower trapezius; serratus anterior; teres major; upper and lower latissimus dorsi; and upper and lower pectoralis major; fine wire electrodes: supraspinatus, infraspinatus, subscapularis, and rhomboid major) using a telemetric electromyography (EMG) system. Five ER exercises (standing ER at 0° and 90° of abduction, with underarm towel roll, prone ER at 90° of abduction, side-lying ER with underarm towel) were studied. Exercise EMG amplitudes were normalized to EMG at maximum ER force in a standard position. Univariate analysis of variance and post hoc analysis applied on EMG activity of each muscle were used to assess the main effect of the exercise condition.

Results:

Muscular activity differed significantly among the ER exercises (P < .05 to P < .001). The greatest activation for anterior and middle deltoid, supraspinatus, upper trapezius, and serratus anterior occurred during standing ER at 90° of abduction; for posterior deltoid, middle trapezius, and rhomboid during side-lying ER with underarm towel; for lower trapezius, upper and lower latissimus dorsi, subscapularis, and teres major during prone ER at 90° of abduction; and for the clavicular and sternal part of the pectoralis major during standing ER with underarm towel.

Conclusion:

Key glenohumeral and scapular muscles can be optimally activated during specific ER exercises, particularly in positions that stimulate athletic overhead motions.

Clinical Relevance:

These results enable sports medicine professionals to target specific muscles during shoulder rehabilitation protocols while minimizing the effect of others, providing a foundation for optimal evidence-based exercise prescription. They also provide information for tailored muscle training and injury prevention in overhead sports.

Shoulder Coordination During Full-Can and Empty-Can Rehabilitation Exercises

CONTEXT

Supraspinatus tear is a common rotator cuff injury. During rehabilitation, debate persists regarding the most appropriate exercises. Whereas shoulder coordination is part of normal arm function, it has been infrequently considered in the context of exercise selection.

OBJECTIVE

To assess shoulder-motion coordination during 2 common supraspinatus rehabilitation exercises and to characterize load and motion-direction influences on shoulder coordination.

DESIGN

Descriptive laboratory study.

SETTING

Motion-analysis laboratory. Patient or Other Participants :  Fifteen asymptomatic right-hand-dominant men (age = 26 ± 4 years, height = 1.77 ± 0.06 m, mass = 74.3 ± 7.7 kg).

INTERVENTION(S)

Full-can and empty-can exercises with and without a 2.27-kg load.

MAIN OUTCOME MEASURE(S)

We recorded motion with an optoelectronic system. Scapulohumeral rhythm and complete shoulder joint kinematics were calculated to quantify shoulder coordination. The effects of exercise type, load, motion direction, and humerothoracic-elevation angle on the scapulohumeral rhythm and shoulder-joint angles were assessed.

RESULTS

We observed multivariate interactions between exercise type and humerothoracic elevation and between load and humerothoracic elevation. Scapulohumeral rhythm increased by a mean ratio of 0.44 ± 0.22 during the full-can exercise, whereas the addition of load increased mean glenohumeral elevation by 4° ± 1°.

CONCLUSIONS

The full-can exercise increased the glenohumeral contribution, as hypothesized, and showed normal shoulder coordination. During the empty-can exercise, the increased scapulothoracic contribution was associated with a compensatory pattern that limits the glenohumeral contribution. Using loads during shoulder rehabilitation seems justified because the scapulohumeral rhythm is similar to that of unloaded arm elevation. Finally, motion direction showed a limited effect during the exercises in healthy individuals.

The effects of finger extension on shoulder muscle activity

[Purpose] This study aims to examine the effects of the extension of the fingers (distal upper limb) on the activity of the shoulder muscles (proximal upper limb). [Subjects and Methods] This study involved 14 healthy male adults with no musculoskeletal disorder or pain related to the shoulders and hands. The subjects in a sitting posture abducted the angle of the shoulder joints at 60° and had their palms in the front direction. Electromyography (EMG) was comparatively analyzed to look at the activities of the infraspinatus (IS) and rhomboid major (RM) when the fingers were extended and relaxed. [Results] The activity of the IS was statistically significantly higher when the fingers were extended than when they were relaxed. [Conclusion] According to the result of this study, finger extension is considered to affect the muscles for connected shoulder joint stability.

Verification of a standardized method for inserting intramuscular electromyography electrodes into teres minor using ultrasound

The close proximity of the infraspinatus to the teres minor and their functional similarity in producing external rotation of the glenohumeral joint make accurate insertion of electromyographic (EMG) electrodes into the teres minor difficult and questionable even when published guidelines are followed. The primary aim of this study was to examine the anatomical support for the current guidelines for inserting intramuscular EMG electrodes into the teres minor muscle. The secondary aim was to provide a technical description for ultrasound-guided electrode insertion into the teres minor. Intramuscular electrodes were inserted into four cadaveric shoulders using markings based on the current guidelines. EMG electrodes were also inserted into the teres minor of four healthy male participants using real-time ultrasound (RTUS) guidance. Systematic dissections of the cadaver specimens revealed that the electrode had been successfully inserted into the teres minor muscle in only one out of the four. In the remaining three specimens, the needle lodged in the infraspinatus muscle belly at distances ranging from 3 to 17 mm medial to the teres minor. Using RTUS guidance, the electrodes were successfully inserted into the teres minor in all participants, as confirmed by visual inspection with RTUS. This study confirms that the current EMG electrode insertion guidelines for the teres minor are not accurate and RTUS ensures the placement of electrodes into the teres minor rather than the adjacent infraspinatus muscle.

Muscular activation during plyometric exercises in 90° of glenohumeral joint abduction

BACKGROUND

Plyometric exercises are frequently used to increase posterior rotator cuff and periscapular muscle strength and simulate demands and positional stresses in overhead athletes. The purpose of this study was to provide descriptive data on posterior rotator cuff and scapular muscle activation during upper extremity plyometric exercises in 90° of glenohumeral joint abduction.

HYPOTHESIS

Levels of muscular activity in the posterior rotator cuff and scapular stabilizers will be high during plyometric shoulder exercises similar to previously reported electromyographic (EMG) levels of shoulder rehabilitation exercises.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Twenty healthy subjects were tested using surface EMG during the performance of 2 plyometric shoulder exercises: prone external rotation (PERP) and reverse catch external rotation (RCP) using a handheld medicine ball. Electrode application included the upper and lower trapezius (UT and LT, respectively), serratus anterior (SA), infraspinatus (IN), and the middle and posterior deltoid (MD and PD, respectively) muscles. A 10-second interval of repetitive plyometric exercise (PERP) and 3 repetitions of RCP were sampled. Peak and average normalized EMG data were generated.

RESULTS

Normalized peak and average IN activity ranged between 73% and 102% and between 28% and 52% during the plyometric exercises, respectively, with peak and average LT activity measured between 79% and 131% and between 31% and 61%. SA activity ranged between 76% and 86% for peak and between 35% and 37% for average activity. Muscular activity levels in the MD and PD ranged between 49% and 72% and between 12% and 33% for peak and average, respectively.

CONCLUSION

Moderate to high levels of muscular activity were measured in the rotator cuff and scapular stabilizers during these plyometric exercises with the glenohumeral joint abducted 90°.

Manual therapy and exercise for adhesive capsulitis (frozen shoulder)

BACKGROUND

Adhesive capsulitis (also termed frozen shoulder) is commonly treated by manual therapy and exercise, usually delivered together as components of a physical therapy intervention. This review is one of a series of reviews that form an update of the Cochrane review, 'Physiotherapy interventions for shoulder pain.'

OBJECTIVES

To synthesise available evidence regarding the benefits and harms of manual therapy and exercise, alone or in combination, for the treatment of patients with adhesive capsulitis.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, CINAHL Plus, ClinicalTrials.gov and the WHO ICTRP clinical trials registries up to May 2013, unrestricted by language, and reviewed the reference lists of review articles and retrieved trials, to identify potentially relevant trials.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-randomised trials, including adults with adhesive capsulitis, and comparing any manual therapy or exercise intervention versus placebo, no intervention, a different type of manual therapy or exercise or any other intervention. Interventions included mobilisation, manipulation and supervised or home exercise, delivered alone or in combination. Trials investigating the primary or adjunct effect of a combination of manual therapy and exercise were the main comparisons of interest. Main outcomes of interest were participant-reported pain relief of 30% or greater, overall pain (mean or mean change), function, global assessment of treatment success, active shoulder abduction, quality of life and the number of participants experiencing adverse events.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion, extracted the data, performed a risk of bias assessment and assessed the quality of the body of evidence for the main outcomes using the GRADE approach.

MAIN RESULTS

We included 32 trials (1836 participants). No trial compared a combination of manual therapy and exercise versus placebo or no intervention. Seven trials compared a combination of manual therapy and exercise versus other interventions but were clinically heterogeneous, so opportunities for meta-analysis were limited. The overall impression gained from these trials is that the few outcome differences between interventions that were clinically important were detected only up to seven weeks. Evidence of moderate quality shows that a combination of manual therapy and exercise for six weeks probably results in less improvement at seven weeks but a similar number of adverse events compared with glucocorticoid injection. The mean change in pain with glucocorticoid injection was 58 points on a 100-point scale, and 32 points with manual therapy and exercise (mean difference (MD) 26 points, 95% confidence interval (CI) 15 points to 37 points; one RCT, 107 participants), for an absolute difference of 26% (15% to 37%). Mean change in function with glucocorticoid injection was 39 points on a 100-point scale, and 14 points with manual therapy and exercise (MD 25 points, 95% CI 35 points to 15 points; one RCT, 107 participants), for an absolute difference of 25% (15% to 35%). Forty-six per cent (26/56) of participants reported treatment success with manual therapy and exercise compared with 77% (40/52) of participants receiving glucocorticoid injection (risk ratio (RR) 0.6, 95% CI 0.44 to 0.83; one RCT, 108 participants), with an absolute risk difference of 30% (13% to 48%). The number reporting adverse events did not differ between groups: 56% (32/57) reported events with manual therapy and exercise, and 53% (30/57) with glucocorticoid injection (RR 1.07, 95% CI 0.76 to 1.49; one RCT, 114 participants), with an absolute risk difference of 4% (-15% to 22%). Group differences in improvement in overall pain and function at six months and 12 months were not clinically important.We are uncertain of the effect of other combinations of manual therapy and exercise, as most evidence is of low quality. Meta-analysis of two trials (86 participants) suggested no clinically important differences between a combination of manual therapy, exercise, and electrotherapy for four weeks and placebo injection compared with glucocorticoid injection alone or placebo injection alone in terms of overall pain, function, active range of motion and quality of life at six weeks, six months and 12 months (though the 95% CI suggested function may be better with glucocorticoid injection at six weeks). The same two trials found that adding a combination of manual therapy, exercise and electrotherapy for four weeks to glucocorticoid injection did not confer clinically important benefits over glucocorticoid injection alone at each time point. Based on one high quality trial (148 participants), following arthrographic joint distension with glucocorticoid and saline, a combination of manual therapy and supervised exercise for six weeks conferred similar effects to those of sham ultrasound in terms of overall pain, function and quality of life at six weeks and at six months, but provided greater patient-reported treatment success and active shoulder abduction at six weeks. One trial (119 participants) found that a combination of manual therapy, exercise, electrotherapy and oral non-steroidal anti-inflammatory drug (NSAID) for three weeks did not confer clinically important benefits over oral NSAID alone in terms of function and patient-reported treatment success at three weeks.On the basis of 25 clinically heterogeneous trials, we are uncertain of the effect of manual therapy or exercise when not delivered together, or one type of manual therapy or exercise versus another, as most reported differences between groups were not clinically or statistically significant, and the evidence is mostly of low quality.

AUTHORS' CONCLUSIONS

The best available data show that a combination of manual therapy and exercise may not be as effective as glucocorticoid injection in the short-term. It is unclear whether a combination of manual therapy, exercise and electrotherapy is an effective adjunct to glucocorticoid injection or oral NSAID. Following arthrographic joint distension with glucocorticoid and saline, manual therapy and exercise may confer effects similar to those of sham ultrasound in terms of overall pain, function and quality of life, but may provide greater patient-reported treatment success and active range of motion. High-quality RCTs are needed to establish the benefits and harms of manual therapy and exercise interventions that reflect actual practice, compared with placebo, no intervention and active interventions with evidence of benefit (e.g. glucocorticoid injection).

Differences in Muscle Activities of the Infraspinatus and Posterior Deltoid during Shoulder External Rotation in Open Kinetic Chain and Closed Kinetic Chain Exercises

[Purpose] This study investigated the changes in electromyographic (EMG) activities of the infraspinatus and posterior deltoid muscles during shoulder external rotation under open kinetic chain (OKC) and closed kinetic chain (CKC) exercise conditions. [Subjects] In total, 15 healthy males participated in this study. [Methods] Subjects performed shoulder external rotations under CKC and OKC conditions while standing with and without weight support provided by a height-adjustable table. Pressure biofeedback was used to ensure a constant amount of weight support. The activities of the infraspinatus and posterior deltoid muscles during shoulder external rotation were measured using a wireless surface EMG system. The paired t-test was used to compare the EMG activities of the infraspinatus and the posterior deltoid muscles and the ratio of the infraspinatus to the posterior deltoid during shoulder external rotation under OKC and CKC conditions. [Results] The EMG activity of the infraspinatus and the ratio of the infraspinatus to the posterior deltoid activities were significantly increased, whereas the posterior deltoid activity was significantly decreased under the CKC condition compared to the OKC condition. [Conclusion] Clinicians should consider the CKC shoulder external rotation exercise when they wish to selectively strengthen the infraspinatus.

Changes in Shoulder External Rotator Muscle Activity during Shoulder External Rotation in Various Arm Positions in the Sagittal Plane

[Purpose] The aim of this study was to investigate changes in electromyographic (EMG) activity of the infraspinatus and posterior deltoid muscles during shoulder external rotation under different shoulder flexion angles. [Subjects] Thirteen participants were included in this study. [Methods] The participants performed isometric shoulder external rotation at 45°, 90°, and 135° of shoulder flexion. A surface EMG system recorded the EMG activity of the infraspinatus and posterior deltoid muscles during shoulder external rotation. The changes in the muscle activity of infraspinatus and posterior deltoid and ratio of infraspinatus to posterior deltoid muscle activity were analyzed using one-way repeated-measures analysis of variance with Bonferroni’s correction. [Results] The posterior deltoid activity was significantly decreased, while the ratio of the infraspinatus to posterior deltoid activity was significantly increased at 45° of shoulder flexion compared with 90° and 135° of shoulder flexion (p < 0.05). There were no significant differences in the EMG activity of the infraspinatus among the three conditions (p > 0.05). [Conclusion] These findings indicate that shoulder external rotation at 45° of shoulder flexion effectively reduced the contribution of the posterior deltoid activation to shoulder external rotation.

Current concepts in examination and treatment of elbow tendon injury

Context:

Injuries to the tendons of the elbow occur frequently in the overhead athlete, creating a significant loss of function and dilemma to sports medicine professionals. A detailed review of the anatomy, etiology, and pathophysiology of tendon injury coupled with comprehensive evaluation and treatment information is needed for clinicians to optimally design treatment programs for rehabilitation and prevention.

Evidence Acquisitions:

The PubMed database was searched in January 2012 for English-language articles pertaining to elbow tendon injury.

Results:

Detailed information on tendon pathophysiology was found along with incidence of elbow injury in overhead athletes. Several evidence-based reviews were identified, providing a thorough review of the recommended rehabilitation for elbow tendon injury.

Conclusions:

Humeral epicondylitis is an extra-articular tendon injury that is common in athletes subjected to repetitive upper extremity loading. Research is limited on the identification of treatment modalities that can reduce pain and restore function to the elbow. Eccentric exercise has been studied in several investigations and, when coupled with a complete upper extremity strengthening program, can produce positive results in patients with elbow tendon injury. Further research is needed in high-level study to delineate optimal treatment methods.

A reliability of electromyographic normalization methods for the infraspinatus muscle in healthy subjects

The purpose of this study was to examine the test-retest reliability of normalization methods for the infraspinatus muscle in a group of healthy subjects. Twelve healthy subjects (male=8, female=4) performed the maximal voluntary isometric contraction (MVIC) with examiner`s resistance, MVIC with a digital tension-meter (MVIC-DT), and sub-MVIC methods. Surface electromyography (EMG) signals were recorded from the infraspinatus muscles according to normalization methods. Reliability was analyzed using the intra-class coefficient (ICC), standard error of measurement (SEM), and minimal detectable difference (MDD). The results of the present study demonstrated that the sub-MVIC method has excellent test-retest reliability (ICC=0.92) with a relatively small SEM (5.9 mV) and MDD₉₅ (16.4 mV), compared to MVIC-DT (ICC=0.73; SEM=11.2 mV; MDD₉₅: 31 mV) and MVIC-E (ICC=0.5; SEM=15.7 mV; MDD₉₅: 43.6 mV). These findings provide evidence that sub-MVIC is more appropriate for comparing the EMG activity for the infraspinatus muscle as a normalization method. If MVIC for normalization is needed, MVIC-DT is more appropriate than MVIC-E.

Selective activation of the infraspinatus muscle

CONTEXT

To improve selective infraspinatus muscle strength and endurance, researchers have recommended selective shoulder external-rotation exercise during rehabilitation or athletic conditioning programs. Although selective strengthening of the infraspinatus muscle is recommended for therapy and training, limited information is available to help clinicians design a selective strengthening program.

OBJECTIVE

To determine the most effective of 4 shoulder external-rotation exercises for selectively stimulating infraspinatus muscle activity while minimizing the use of the middle trapezius and posterior deltoid muscles.

DESIGN

Cross-sectional study.

SETTING

University research laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 30 healthy participants (24 men, 6 women; age = 22.6 ± 1.7 years, height = 176.2 ± 4.5 cm, mass = 65.6 ± 7.4 kg) from a university population.

INTERVENTION(S)

The participants were instructed to perform 4 exercises: (1) prone horizontal abduction with external rotation (PER), (2) side-lying wiper exercise (SWE), (3) side-lying external rotation (SER), and (4) standing external-rotation exercise (STER).

MAIN OUTCOME MEASURE(S)

Surface electromyography signals were recorded from the infraspinatus, middle trapezius, and posterior deltoid muscles. Differences among the exercise positions were tested using a 1-way repeated-measures analysis of variance with Bonferroni adjustment.

RESULTS

The infraspinatus muscle activity was greater in the SWE (55.98% ± 18.79%) than in the PER (46.14% ± 15.65%), SER (43.38% ± 22.26%), and STER (26.11% ± 15.00%) (F3,87 = 19.97, P < .001). Furthermore, the SWE elicited the least amount of activity in the middle trapezius muscle (F3,87 = 20.15, P < .001). Posterior deltoid muscle activity was similar in the SWE and SER but less than that measured in the PER and STER (F3,87 = 25.10, P < .001).

CONCLUSIONS

The SWE was superior to the PER, SER, and STER in maximizing infraspinatus activity with the least amount of middle trapezius and posterior deltoid activity. These findings may help clinicians design effective exercise programs.

Shoulder external rotation fatigue and scapular muscle activation and kinematics in overhead athletes

CONTEXT

Glenohumeral external rotation (GH ER) muscle fatigue might contribute to shoulder injuries in overhead athletes. Few researchers have examined the effect of such fatigue on scapular kinematics and muscle activation during a functional movement pattern.

OBJECTIVE

To examine the effects of GH ER muscle fatigue on upper trapezius, lower trapezius, serratus anterior, and infraspinatus muscle activation and to examine scapular kinematics during a diagonal movement task in overhead athletes.

SETTING

Human performance research laboratory.

DESIGN

Descriptive laboratory study.

PATIENTS OR OTHER PARTICIPANTS

Our study included 25 overhead athletes (15 men, 10 women; age = 20 ± 2 years, height = 180 ± 11 cm, mass = 80 ± 11 kg) without a history of shoulder pain on the dominant side.

INTERVENTION(S)

We tested the healthy, dominant shoulder through a diagonal movement task before and after a fatiguing exercise involving low-resistance, high-repetition, prone GH ER from 0° to 75° with the shoulder in 90° of abduction.

MAIN OUTCOME MEASURE(S)

Surface electromyography was used to measure muscle activity for the upper trapezius, lower trapezius, serratus anterior, and infraspinatus. An electromyographic motion analysis system was used to assess 3-dimensional scapular kinematics. Repeated-measures analyses of variance (phase × condition) were used to test for differences.

RESULTS

We found a decrease in ascending-phase and descending-phase lower trapezius activity (F(1,25) = 5.098, P = .03) and an increase in descending-phase infraspinatus activity (F(1,25) = 5.534, P = .03) after the fatigue protocol. We also found an increase in scapular upward rotation (F(1,24) = 3.7, P = .04) postfatigue.

CONCLUSIONS

The GH ER muscle fatigue protocol used in this study caused decreased lower trapezius and increased infraspinatus activation concurrent with increased scapular upward rotation range of motion during the functional task. This highlights the interdependence of scapular and glenohumeral force couples. Fatigue-induced alterations in the lower trapezius might predispose the infraspinatus to injury through chronically increased activation.

Three-dimensional evaluation of cyclic displacement in single-row and double-row rotator cuff reconstructions under static external rotation

BACKGROUND

The double-row suture bridge repair was recently introduced and has demonstrated superior biomechanical results and higher yield load compared with the traditional double-row technique. It therefore seemed reasonable to compare this second generation of double-row constructs to the modified single-row double mattress reconstruction.

HYPOTHESIS

The repair technique, initial tear size, and tendon subregion will have a significant effect on 3-dimensional (3D) cyclic displacement under additional static external rotation of a modified single-row compared with a double-row rotator cuff repair.

STUDY DESIGN

Controlled laboratory study.

METHODS

Rotator cuff tears (small to medium: 25 mm; medium to large: 35 mm) were created in 24 human cadaveric shoulders. Rotator cuff repairs were performed as modified single-row or double-row repairs, and cyclic loading (10-60 N, 10-100 N) was applied under 20° of external rotation. Radiostereometric analysis was used to calculate cyclic displacement in the anteroposterior (x), craniocaudal (y), and mediolateral (z) planes with a focus on the repair constructs and the initial tear size. Moreover, differences in cyclic displacement of the anterior compared with the posterior tendon subregions were calculated.

RESULTS

Significantly lower cyclic displacement was seen in small to medium tears for the single-row compared with double-row repair at 60 and 100 N in the x plane (P = .001) and y plane (P = .001). The results were similar in medium to large tears at 100 N in the x plane (P = .004). Comparison of 25-mm versus 35-mm tears did not show any statistically significant differences for the single-row repairs. In the double-row repairs, lower gap formation was found for the 35-mm tears (P ≤ .05). Comparison of the anterior versus posterior tendon subregions revealed a trend toward higher anterior gap formation, although this was statistically not significant.

CONCLUSION

The tested single-row reconstruction achieved superior results in 3D cyclic displacement to the tested double-row repair. Extension of the initial rupture size did not have a negative effect on the biomechanical results of the tested constructs.

CLINICAL RELEVANCE

Single-row repairs with modified suture configurations provide comparable biomechanical strength to double-row repairs. Furthermore, as increased gap formation in the early postoperative period might lead to failure of the construct, a strong anterior fixation and restricted external rotation protocol might be considered in rotator cuff repairs to avoid this problem.

Therapeutic exercise for athletes with nonspecific neck pain: a current concepts review

Context:

Benign neck pain is common in athletes and is usually the result of minor sprains, strains, or contusions. Athletes with neck pain may have deficits in cervical and/or upper thoracic mobility, muscle recruitment, strength and endurance, repositioning acuity, postural stability, and oculomotor control.

Evidence Acquisition:

A Medline search was performed via PubMed to locate articles of any publication date through December 2011 using the search terms cervical pain, neck pain, athlete, athletic, therapeutic exercise, and rehabilitation. Reference lists of retrieved articles were searched for additional relevant references.

Results:

Therapeutic exercise has promise as an intervention for individuals with neck pain, although reports on isolated athletic populations are lacking. To date, recommendations for specific therapeutic exercises have been derived largely from anecdotal or uncontrolled level IV or V evidence.

Conclusion:

Clinicians should consider deficits, functional limitations, irritability level, and the sport’s cervical spine stress profile when selecting exercises for athletes with neck pain.

A new manual muscle test for assessing the entire trapezius muscle

Manual muscle testing (MMT), the trapezius muscle is an important part of the examination in patients with upper extremity dysfunction or pain.

PURPOSE

The purpose of this study was to assess the reliability and validity of a new MMT that assesses the entire trapezius muscle instead of the usual method of separating it into three different parts. The new trapezius MMT is similar to the serratus anterior muscle test; however, the testing is performed in the frontal versus sagittal plane.

METHODS

A convenience sample of 11 subjects was recruited with no known shoulder pathology. Surface electromyography electrodes were placed on the upper, middle, and lower trapezius fibers according to a previously validated method and MMTs for the three different trapezius muscle test positions were normalized against the new trapezius test position.

RESULTS

The new trapezius MMT showed very high maximal voluntary isometric contraction (MVIC; 160.80%) for the upper trapezius muscle, high for the middle trapezius muscle (59.23%), and high for the lower trapezius muscle (47.54%) when normalized against the MVICs for each individual trapezius muscle tests.

CONCLUSIONS

A new MMT that assesses the whole trapezius in its role as an upward scapular rotator was found to be reliable and valid.

Electromyographical comparison of four common shoulder exercises in unstable and stable shoulders

This study examines if electromyographic (EMG) amplitude differences exist between patients with shoulder instability and healthy controls performing scaption, prone horizontal abduction, prone external rotation, and push-up plus shoulder rehabilitation exercises. Thirty nine subjects were categorized by a single orthopedic surgeon as having multidirectional instability (n = 10), anterior instability (n = 9), generalized laxity (n = 10), or a healthy shoulder (n = 10). Indwelling and surface electrodes were utilized to measure EMG activity (reported as a % of maximum voluntary isometric contraction (MVIC)) in various shoulder muscles during 4 common shoulder exercises. The exercises studied effectively activated the primary musculature targeted in each exercise equally among all groups. The serratus anterior generated high activity (50–80% MVIC) during a push-up plus, while the infraspinatus and teres major generated moderate-to-high activity (30–80% MVIC) during both the prone horizontal and prone external rotation exercises. Scaption exercise generated moderate activity (20–50% MVIC) in both rotator cuff and scapular musculature. Clinicians should feel confident in prescribing these shoulder-strengthening exercises in patients with shoulder instability as the activation levels are comparable to previous findings regarding EMG amplitudes and should improve the dynamic stabilization capability of both rotator cuff and scapular muscles using exercises designed to address glenohumeral joint instability.

Infraspinatus fatigue during resisted arm elevation with isometric contraction: an electromyographic study

BACKGROUND

Various forms of resistance are used in rotator cuff training programs. However, the muscular activity of the infraspinatus during arm elevation has not been clarified in detail. We aimed to evaluate infraspinatus fatigue during resisted arm elevation in various positions.

METHODS

The dominant (right) shoulders of 39 healthy subjects were examined. Average mean power frequency shifts of the infraspinatus and deltoid were evaluated electromyographically when the subjects performed isometric contractions equivalent to 30% of the maximal voluntary isometric contraction force for 60 s during 90° arm elevation in the sagittal and scapular planes, prone and side-lying external rotations, and repeated side-lying external rotation exercise. Further, the arm-elevation force was measured before and after the repeated external rotation exercise. Analysis of variance and paired t tests were used for statistical analyses; differences at P < .05 were considered significant.

RESULTS

The infraspinatus was fatigued easily during resisted arm elevation in the sagittal plane compared with the scapular plane (P < .01). Comparisons of sagittal-plane elevation with side-lying and prone external rotations revealed no significant differences in the fatigue levels. The arm-elevation force after the repeated external rotations was significantly decreased in the sagittal plane compared with the scapular plane (P < .01).

CONCLUSION

In clinical settings, this data may be helpful in knowing how to helpful to protect the infraspinatus after surgical repair. Therefore, therapeutic exercise regimes with resisted arm elevation should avoid infraspinatus overfatigue in the sagittal plane in the early postoperative period.

Kinetic chain rehabilitation: a theoretical framework

Sequenced physiologic muscle activations in the upper and lower extremity result in an integrated biomechanical task. This sequencing is known as the kinetic chain, and, in upper extremity dominant tasks, the energy development and output follows a proximal to distal sequencing. Impairment of one or more kinetic chain links can create dysfunctional biomechanical output leading to pain and/or injury. When deficits exist in the preceding links, they can negatively affect the shoulder. Rehabilitation of shoulder injuries should involve evaluation for and restoration of all kinetic chain deficits that may hinder kinetic chain function. Rehabilitation programs focused on eliminating kinetic chain deficits, and soreness should follow a proximal to distal rationale where lower extremity impairments are addressed in addition to the upper extremity impairments. A logical progression focusing on flexibility, strength, proprioception, and endurance with kinetic chain influence is recommended.

Muscle loading and activation of the shoulder joint during humeral external rotation by pulley and variable resistance

BACKGROUND

The aim of the study was to evaluate differences in the loading of glenohumeral joint muscles between a cable pulley machine (CP) and variable resistance machine (VR) during axial humeral external rotation.

METHODS

Eleven healthy male subjects took part in the study. Intramuscular electromyography from five muscles of the shoulder (medial deltoid, supraspinatus, infraspinatus and upper part of the trapezius), torque and power output was measured at different rotation angles and with different loads (10%, 50% and 100% of 1RM). Also the compressive and shear force in the glenohumeral joint was analyzed at the horizontal level at angles of rotation. External rotation was performed with a self-selected velocity on the scapular plane.

FINDINGS

In the CP the range of movement became narrower than in the VR with increasing workload (P<0.05). The activity of the infraspinatus did not grow in the CP after 50% load, while it did in the VR (P<0.01). The upper part of the trapezius was activated less in the CP than in the VR (P<0.01) machine when using 50% and 100% loads. In comparison with the CP, the shear forces that pull the head of the humerus in a posterior direction were more evenly distributed in the VR than in the CP at different angles of rotation (P<0.001).

INTERPRETATION

The VR seems to make a broader range of motion possible, lager activation the primary external rotators and evenly distributed shear forces than the CP. However, performing the exercise with VR and high load also activates the upper part of the trapezius.

RELEVANCE

These findings can be used in the development of exercise designs, methods and equipment for shoulder injury rehabilitation.

Scapulothoracic and scapulohumeral exercises: a narrative review of electromyographic studies

STUDY DESIGN

Narrative review.

INTRODUCTION

A well-constructed rehabilitation program of the shoulder complex is critical to stabilizing the scapulothoracic and scapulohumeral joints while encouraging normal scapulohumeral rhythm. Review of the literature demonstrates a variety of scapulothoracic and glenohumeral conditioning exercises.

PURPOSE

To assist the occupational and physical therapist in prioritizing exercises for a shoulder conditioning program based on a narrative review of electromyographic (EMG) studies of the shoulder.

METHODS

The authors performed a comprehensive literature search of approximately 250 articles describing shoulder (EMG) testing of the rotator cuff and periscapular musculature. Twenty-two articles were selected based on the author's inclusion criteria. The authors developed a flow sheet outlining each exercise, starting and ending positions, principle muscle(s), and description of exercise. Exercises were assigned to two different muscle groups: rotator cuff or periscapular depending on the principle muscles activated.

RESULTS

The 22 included articles provided an evidenced-based list of exercises aimed to efficiently and maximally recruit specific rotator cuff and periscapular musculature. Based on these 22 articles, the authors were able to establish a useful series of exercises to promote glenohumeral stability and foster normal scapulohumeral rhythm. Those exercises that elicited the highest maximum voluntary isometric contraction recruitment and were cited to be critical for stability and scapulohumeral rhythm were selected for the exercise flow sheet.

CONCLUSIONS

This review provides a useful evidence-based tool to establish a practical shoulder exercise program.

LEVEL OF EVIDENCE

Level 5.

Muscle activity of the core during bilateral, unilateral, seated and standing resistance exercise

Little is known about the effect of performing common resistance exercises standing compared to seated and unilaterally compared to bilaterally on muscle activation of the core. Thus, the purpose of this study was to compare the electromyographic activity (EMG) of the superficial core muscles (i.e. rectus abdominis, external oblique and erector spinae) between seated, standing, bilateral and unilateral dumbbell shoulder presses. 15 healthy males performed five repetitions at 80% of one-repetition maximum of the exercises in randomized order. Results were analyzed with a two-way analysis of variance and a Bonferroni post hoc test. The position × exercise interaction was significantly different for rectus abdominis (P = 0.016), but not for external oblique (P = 0.100) and erector spinae (P = 0.151). The following EMG results were observed: For rectus abdominis: ~49% lower in seated bilateral versus unilateral (P < 0.001), similar in standing bilateral versus unilateral (P = 0.408), ~81% lower in bilateral seated versus standing (P < 0.001), ~59% lower in unilateral seated versus standing (P < 0.001); For external oblique: ~81% lower in seated bilateral versus unilateral (P < 0.001), ~68% lower in standing bilateral than unilateral (P < 0.001), ~58% lower in bilateral seated versus standing (P < 0.001), ~28% lower in unilateral seated versus standing (P = 0.002); For erector spinae: similar in seated bilateral versus unilateral (P = 0.737), ~18% lower in standing bilateral versus unilateral (P = 0.001), similar in seated versus standing bilateral (P = 0.480) and unilateral (P = 0.690). In conclusion, to enhance neuromuscular activation of the superficial core muscles, standing exercises should be used instead of seated exercises, and unilateral exercises should be used instead of bilateral exercises.

Razão eletromiográfica de músculos estabilizadores do ombro durante a execução de exercícios com haste oscilatória

Os processos de dor e disfunção do ombro são muito comuns e demandam grande atenção por parte dos profissionais que treinam e reabilitam esta articulação. O excesso de ativação do músculo trapézio superior (TS) combinado com a diminuição da ativação do trapézio inferior (TI) têm sido proposto como fator contribuinte para lesões no ombro. Diversos equipamentos são usados no treinamento e reabilitação destes músculos como faixas elásticas, cargas livres e, recentemente, hastes oscilatórias. Apesar de muito utilizada no contexto clínico e desportivo, pouco se sabe acerca dos efeitos destas hastes sobre o recrutamento dos músculos estabilizadores de ombro. Assim, o objetivo do presente estudo foi determinar a razão de ativação entre os músculos TS e TI em diferentes exercícios realizados com haste oscilatória. Participaram do estudo 12 indivíduos do sexo feminino, jovens (20,4 ± 2,0 anos), fisicamente ativas. O sinal eletromiográfico dos músculos TS e TI foi coletado durante a execução de três diferentes exercícios realizados com a haste oscilatória. A análise dos dados eletromiográficos foi feita a partir dos valores de root mean square (RMS) pelo cálculo da razão entre os músculos TS e TI para cada exercício. Para análise estatística foram utilizados os testes ANOVA para medidas repetidas e post hoc de Bonferroni, considerando como nível de significância p < 0,05. O exercício III apresentou menor razão entre os músculos TS e TI (0,722), seguido pelos exercícios I e II, respectivamente (0,876 e 0,995). CONCLUSÃO: O uso da haste oscilatória em exercícios executados unimanualmente no plano sagital e com a haste perpendicular ao solo são recomendados para o treinamento e reabilitação dos músculos estabilizadores da escápula por promoverem menor ativação do TS em relação o TI

Clinical concepts for treatment of the elbow in the adolescent overhead athlete

Injuries to the adolescent elbow are common because of the repetitive overuse inherent in many overhead sport activities. The management of these patients is greatly facilitated through a greater understanding of the demands placed on the upper extremity kinetic chain during these overhead activities as well as a detailed examination and rehabilitation for the entire upper extremity kinetic chain. Particular emphasis on improving rotator cuff strength and muscular endurance, along with scapular stabilization, is a critical part of elbow rehabilitation in these patients. In addition, the use of a strategic and progressive interval sport return program is necessary to minimize reinjury and return the adolescent overhead athlete to full function.