Acromiohumeral Distance During Neuromuscular Electrical Stimulation of the Lower Trapezius and Serratus Anterior Muscles in Healthy Participants

Neuromuscular electrical stimulation of humeral adductors in subjects with rotator cuff tear

INTRODUCTION

In symptomatic patients with rotator cuff tear, MRI and radiographic studies have ascribed the pain symptom to insufficient humeral head depression during arm elevations. The arm adductors such as the teres major and pectoralis major may contribute to depression of the humerus head during arm elevations. Researchers have demonstrated that neuromuscular electrical stimulation (NMES) of the serratus anterior and lower trapezius can control scapular motions and improve acromiohumeral distance. It is unknown, however, if adductor neuromuscular training could help patients with rotator cuff tear.

MATERIALS AND METHODS

A cross-sectional study of NMES of the teres major and pectoralis major was conducted on 30 symptomatic subjects with rotator cuff tear. We measured the acromiohumeral distance by ultrasonography and scapular kinematics during arm elevation with a three-dimensional motion tracking system.

RESULTS

The acromiohumeral distance significantly increased during NMES of the teres major (0.73 mm, p < 0.001). However, the distance significantly decreased with NMES of the pectoralis major (0.78 mm, p < 0.001). Additionally, scapular upward rotation was greater during NMES of the teres major than during NMES of the pectoralis major (3.4°, p < 0.001). Scapular external rotation decreased significantly more during NMES of the pectoralis major than during NMES of the teres major (1.6°, p = 0.003).

CONCLUSIONS

NMES of the teres major can increase acromiohumeral distance and scapular upward rotation during arm elevation. However, the decreased upward and external rotation of the scapula during arm elevation with NMES of the pectoralis major may be associated with subacromial impingement.

Acromiohumeral distance quantification during a variety of shoulder external and internal rotational exercises in recreationally overhead athletes

To determine whether shoulder external (ER) and internal rotational (IR) exercises at five different shoulder abduction angles affect the acromiohumeral distance (AHD). Twenty recreational overhead athletes were included. AHD was measured using real-time ultrasound for each of the five shoulder conditions as follows: neutral shoulder rotation (active-hold) and during ER and IR exercises (isometric and concentric) at five different shoulder-abduction angles (0°, 30°, 45°, 60°, and 90° of abduction). A two-way ANOVA was used to analyze AHD values. Shoulder abduction angle × exercise interaction for AHD was found (F16,304 = 10.92; p < .001; η2 = 0.37). For both isometric and concentric conditions, AHD increased during IR exercises (p < .05) yet decreased during ER exercises (p < .05) when compared with each active-hold positions. Shoulder ER and IR exercises influence the AHD in recreational overhead athletes. A larger AHD was observed during shoulder IR exercises, whereas ER exercises failed to maintain the AHD.

The Effectiveness of Neuromuscular Electrical Stimulation in Patients With Subacromial Impingement Syndrome: A Randomized Controlled Study

OBJECTIVE

The aim of the study is to compare the effects of exercise training plus neuromuscular electrical stimulation with exercise training alone on shoulder function, pain, range of motion, and muscle strength in patients with subacromial impingement syndrome.

DESIGN

Patients were randomly divided into groups of exercise training ( n = 24) and exercise training + neuromuscular electrical stimulation ( n = 24). Shoulder function was evaluated with the Disabilities of the Arm, Shoulder and Hand Questionnaire, pain level was assessed with a visual analog scale, range of motion was measured with a goniometer, and muscle strength was assessed with a handheld dynamometer baseline and at the end of treatment (week 8).

RESULTS

In both groups, shoulder function, range of motion, and muscle strength (except flexion muscle strength in the exercise training group) increased, while pain decreased ( P < 0.05). Compared with the exercise training group, visual analog scale-activity and visual analog scale-night decreased more, and external-rotation range of motion and whole muscle strength increased more in the exercise training + neuromuscular electrical stimulation group ( P < 0.05). On the other hand, the effect sizes were medium to large for both groups.

CONCLUSIONS

The addition of neuromuscular electrical stimulation treatment to exercise training did not improve shoulder function, which is the primary outcome, more than exercise training alone, but increased muscle strength and range of motion (external-rotation only) and decreased pain (activity-night), which are the secondary outcomes.

Feasibility and significance of stimulating interscapular muscles using transcutaneous functional electrical stimulation in able-bodied individuals

OBJECTIVE

The study objective was to assess the feasibility of stimulating the lower trapezius (LT), the upper trapezius (UT) and serratus anterior (SA) muscles along with anterior or middle deltoid, using surface functional electrical stimulation (FES). The secondary aim was to understand the effects of LT, UT, and SA stimulation on maximum arm reach achieved in shoulder flexion and abduction.

DESIGN

Single arm interventional study.

SETTING

Inpatient Rehabilitation Hospital.

PARTICIPANTS

Ten healthy volunteers.

INTERVENTION

Participants completed 10 trials for each of the 3 conditions in flexion and abduction, i.e. (1) Active voluntary flexion or abduction, (2) FES for anterior deltoid for flexion or middle deltoid for abduction, and (3) FES for LT, UT, and SA along with anterior deltoid for flexion or middle deltoid for abduction.

OUTCOME MEASURES

Maximum arm reach and percent angle relative to the voluntary movement were computed from motion capture data for each condition. Wilcoxon signed-rank test was used to compare the maximum reach between two FES conditions.

RESULTS

The study results showed that all three interscapular muscles can be stimulated using surface FES. Maximum reach in abduction was greater for FES of middle deltoid along with the interscapular muscles (51.77° ± 17.54°) compared to FES for middle deltoid alone (43.76° ± 15.32°; Z = -2.701, P = 0.007). Maximum reach in flexion for FES of anterior deltoid, along with interscapular muscles, was similar to that during FES of anterior deltoid alone.

CONCLUSION

Interscapular muscles can be stimulated using surface FES devices and should be engaged during rehabilitation as appropriate.

Shoulder-Abduction Angle and Trapezius Muscle Activity During Scapular-Retraction Exercise

CONTEXT

Scapular-retraction exercises are often prescribed to enhance scapular stabilization.

OBJECTIVE

To investigate upper trapezius (UT), middle trapezius (MT), and lower trapezius (LT) activities and UT/MT and UT/LT ratios during scapular-retraction exercises with elastic resistance at different shoulder-abduction angles.

DESIGN

Descriptive laboratory study.

SETTING

Biomechanical analysis laboratory.

PATIENTS OR OTHER PARTICIPANTS

Thirty-five asymptomatic individuals.

MAIN OUTCOME MEASURE(S)

Surface electromyography was used to evaluate UT, MT, and LT activities during the scapular-retraction exercise at 0°, 45°, 90°, and 120° of shoulder abduction.

RESULTS

The mean muscle activity ranged from 15.8% to 54.7% maximal voluntary isometric contraction (MVIC) for UT, 30.5% to 51.6% MVIC for MT, and 21.4% to 25.5% MVIC for LT. A significant muscle × angle interaction was found (P < .001). Post hoc analysis revealed that the MT was more activated than the UT and LT during both retraction at 0° (P < .001 and P = .01, respectively) and 120° (P = .03 and P = .002, respectively). During retraction at 45° and 90°, the LT generated less activity than the UT (P = .02 and P = .03, respectively) and MT (P < .001 and P = .002, respectively). Further, UT/MT and UT/LT ratios during retraction at 0° were lower than at 45° (P = .03 and P = .001, respectively) and 90° (P < .001 and P < .001, respectively). Retraction at 90° resulted in a higher UT/LT ratio than at 45° (P = .004) and 120° (P = .004).

CONCLUSIONS

Due to less UT relative to MT activity, retraction at 0°, 45°, and 120° can be preferable in early shoulder training or rehabilitation. Additionally, retraction at 90° was the most effective exercise in activating all parts of the trapezius muscle.

A Novel Rehabilitation Program Using Neuromuscular Electrical Stimulation (NMES) and Taping for Shoulder Pain in Swimmers: A Protocol and Case Example

In-pool return to swim protocols have been described for swimmers returning from being deactivated from swimming due to a shoulder injury who have full shoulder strength. Many swimmers actively participate in swim practice and competition with shoulder pain and experience deficits in performance. There are multiple reported risk factors associated with shoulder pain among swimmers, including training errors and physical impairments. These include pool and dry-land training errors, weakness in the scapular stabilizers and rotator cuff, and muscle tightness. A need exists for dry-land rehabilitation programs for impairments common to swimmers that can be performed in a traditional outpatient physical therapy setting. The purpose of this clinical commentary is to present a protocol using neuromuscular electrical stimulation (NMES), taping, strengthening, and stretching to address impairments that are common among swimmers while allowing continued active participation in practice and competition.

LEVEL OF EVIDENCE

Level 5.

An electromyographic and kinematic study of the scapular stabilisers

Background

The scapular stabilisers, especially the actions of the force couples around the scapula, have an impact on the biomechanics of the scapula and the orientation of the glenoid.

Objectives

The aim of our study was to determine both the muscle activity and the correlation between the muscle activity ratio of the lower force couple (the serratus anterior lower fibres and the lower trapezius).

Methods

This was a quantitative cross-sectional study. Muscle activity of the dominant serratus anterior lower fibres and the lower trapezius muscles was collected with surface electromyographic (EMG) sensors and an inertial motion capture system was used to measure the three-dimensional (3D) shoulder flexion in the sagittal plane and abduction in the frontal plane. Graph Pad 5 (Prism, San Diego, CA, USA) was used for the statistical analysis. The confidence level was set at 95% (p < 0.05).

Results

Sixteen men and women participated in our study, with a mean (standard deviation) age of 25.4 (± 4.6) years, weight of 80.2 (± 25.1) kg and height of 171.6 (± 10.3) cm. A strong negative correlation was found at the start of the abduction (r = −0.623; p = 0.01) between the muscle activity of the serratus anterior lower fibres and the lower trapezius.

Conclusions

The only significant increase in the mean EMG ratio of serratus anterior lower fibres versus the lower trapezius was present at 60% (from baseline) of abduction (p = 0.03).

Clinical implications

The EMG activity ratio of serratus anterior lower fibres and lower trapezius remains variable in different movement planes.

Shoulder pain and scapular dyskinesis associated with lower trapezius dysplasia - A case report

BACKGROUND

Scapular dyskinesis (SD) has been associated with shoulder soft-tissue tightness as well scapular muscle strength and/or activation deficits. Inadequate development of the trapezius muscle (trapezius dysplasia) is a relatively rare condition inconsistently associated with shoulder dysfunction.

CASE DESCRIPTION

a 24-year old male complaining of left scapular area pain associated with SD and scapular muscle weakness was noted to present with a smaller ipsilateral lower trapezius (LT). Further inquiry including electromyography, rehabilitative ultrasound imaging (RUSI) and magnetic resonance imaging ruled out nerve palsy and demonstrated a hypoplastic left LT. This led to a greater emphasis on serratus anterior (SA) training along with the addition of neuromuscular electrical stimulation of the LT.

OUTCOMES

Following 12 sessions over a 5-month period the patient reported no pain or functional deficits, and was able to resume all recreational activities. The patient's subjective shoulder value increased from 55% to 80%, and LT strength was markedly improved.

DISCUSSION

Scapular muscle dysplasia may represent a less recognized cause of SD. A more thorough inspection of scapular muscle shape and orientation, possibly augmented by RUSI may be indicated in patients presenting with SD. Neuromuscular electrical stimulation is a potentially useful modality for addressing scapular muscle activation and strength deficits and future research into its efficacy under these circumstances may be warranted.

Comparison of mobilization with supervised exercise for patients with subacromial impingement syndrome

Objectives

This study aims to investigate the effects of joint mobilization with supervised exercise in patients with subacromial impingement syndrome (SAIS).

Patients and methods

This prospective, randomized-controlled study included a total of 40 patients (18 males, 22 females; mean age 43.52 years; range, 27 to 67 years) with SAIS of more than six weeks between June 2014 and June 2015. The patients were randomly allocated into two groups: Group 1 (n=20) received joint mobilization and neuromuscular electrical stimulation and Group 2 (n=20) received a supervised exercise program and neuromuscular electrical stimulation. The outcome measures included the range of motion, pain intensity, the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire, American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form-patient self-report section, Short Form-36, and Global Rating of Change Questionnaire. Pain was evaluated using the visual analog scale (VAS).

Results

In both groups, the mean VAS scores significantly decreased and the range of motion significantly increased after treatment (p<0.05). Both joint mobilization and supervised exercise combined with neuromuscular electrical stimulation led to a significant improvement in function in patients with SAIS (p<0.05), although it did not significantly differ between the groups (p>0.05). Patient satisfaction with treatment was similar in both groups (p=0.28).

Conclusion

Based on our study results, mobilization and supervised exercise yield comparable outcomes in patients with SAIS.

Lower Trapezius Weakness and Shoulder Complex Biomechanics during the Tennis Serve

PURPOSE

This study aimed to assess the effect of lower trapezius (LT) weakness on humeral and scapular kinematics and shoulder muscle activity during the tennis serve.

METHODS

Fifteen competitive male tennis players (age, 23.8 ± 3.4 yr; height, 182.8 ± 6.7 cm; mass: 76.6 ± 8.7 kg; tennis experience: 15.6 ± 4.9 yr) performed two tennis serves before and after selective fatigue of the LT (25-min electric muscle stimulation). During each tennis serve, racket, humeral and scapular kinematics and the activity of 13 shoulder muscles were recorded using an optoelectronic system synchronized with indwelling and surface electromyography. The serve was split into five phases, that is, early and late cocking, acceleration, early and late follow-through.

RESULTS

Selective fatigue led to a 22.5% ± 10.4% strength decrease but did not alter maximum racket speed and humerothoracic joint kinematics. However, increased scapular upward rotation was observed in the acceleration (P = 0.02) and early follow-through (P = 0.01) phases. Decreased muscular activity was observed during the early cocking phase for the LT (P = 0.01), during the acceleration phase for the LT (P = 0.01), anterior deltoid (P = 0.03), pectoralis major (P = 0.04), and subscapularis (P = 0.03), and during the early follow-through phase for the anterior deltoid (P = 0.03) and LT (P = 0.04).

CONCLUSIONS

The LT weakness altered neither serve velocity nor humerothoracic joint kinematics, but impaired scapulothoracic kinematics and anterior shoulder muscle activation. Such alterations may reduce the subacromial space and jeopardize humeral head stability. These findings shed new light on the consequences of LT weakness, highlighting the importance of monitoring and strengthening this muscle in overhead athletes.

Relationship Between Middle Trapezius Muscle Activation and Acromiohumeral Distance Change During Shoulder Elevation With Scapular Retraction

CONTEXT

The scapular retraction exercises are widely used among clinicians to balance the activity of the scapular muscles as well as the rotator cuff muscles in different shoulder abduction positions.

OBJECTIVES

The aim of this study was to investigate the relationship between scapular (middle and upper trapezius) and shoulder muscles (middle deltoid and infraspinatus) activation level differences and acromiohumeral distance changes during shoulder abduction with scapular retraction.

DESIGN

Cross-sectional study.

SETTING

University research laboratory.

PARTICIPANTS

Nineteen asymptomatic individuals were included (mean [SD]: age = 22.4 [1.8] y).

MAIN OUTCOME MEASURE

The acromiohumeral distance was measured at 0° and 90° shoulder abduction when the scapula was in nonretracted and retracted position with ultrasound imaging. The relationship between muscle activation level changes and acromiohumeral distance difference was analyzed with the Pearson correlation test.

RESULTS

Middle trapezius muscle activity change correlated with acromiohumeral distance difference (r = .55, P = .02) from 0° to 90° shoulder abduction when scapula was retracted. For both nonretracted and retracted scapular positions, no correlations were found between middle deltoid, infraspinatus, and upper trapezius muscle activity changes with acromiohumeral distance differences during shoulder abduction (P > .05).

CONCLUSIONS

Active scapular retraction exercise, especially focusing on the middle trapezius muscle activation, seems to be an effective treatment option to optimize the acromiohumeral distance during shoulder abduction.

Active Scapular Retraction and Acromiohumeral Distance at Various Degrees of Shoulder Abduction

CONTEXT

  Performing shoulder-abduction exercises with scapular retraction has been theorized to reduce the potential for shoulder impingement. However, objective data to support this premise are lacking.

OBJECTIVE

  To evaluate the influence of active scapular retraction on acromiohumeral distance (AHD) at 4 shoulder-abduction angles using real-time ultrasound.

DESIGN

  Cross-sectional study.

SETTING

  University laboratory.

PATIENTS OR OTHER PARTICIPANTS

  Twenty asymptomatic individuals (10 men, 10 women; age = 22.9 ± 2.8 years, height = 169.3 ± 9.5 cm, mass = 65.5 ± 12.9 kg) were recruited.

MAIN OUTCOME MEASURE(S)

  Real-time ultrasound images of AHD were obtained during nonretracted and retracted scapular conditions at 0°, 45°, 60°, and 90° of shoulder abduction. A 2-factor analysis of variance with repeated measures was used to evaluate the influence of shoulder retraction on AHD across shoulder-abduction angles.

RESULTS

  A scapular-retraction condition × shoulder-abduction-angle interaction for AHD was found ( F_3,57 = 4.56, P = .006). The AHD was smaller at 0° (10.5 versus 11.2 mm, respectively; t₁₉ = 2.22, P = .04) but larger at 90° (9.4 versus 8.7 mm, respectively; t₁₉ = -2.30, P = .04) of shoulder abduction during the retracted than the nonretracted condition. No differences in AHD were observed between conditions at 45° ( t₁₉ = 1.45, P = .16) and 60° ( t₁₉ = 1.17, P = .86) of abduction.

CONCLUSIONS

  The observed differences in AHD at 0° and 90° of shoulder abduction were small and did not exceed the established minimal detectable change for either angle. Our findings suggest that active scapular retraction during shoulder abduction has a minimal influence on AHD at 0° and 90° in healthy individuals. Further investigations are needed to determine whether scapular retraction influences AHD in individuals with subacromial impingement.

Rate of Upper Extremity Injury in High School Baseball Pitchers Who Played Catcher as a Secondary Position

CONTEXT

  Many high school pitchers play another position after they have finished pitching for the day or on their rest days from pitching. Because of the cumulative demands on the arm, pitchers who also play catcher may have a greater risk of developing a throwing-related shoulder or elbow injury.

OBJECTIVE

  To compare the rate of throwing-related upper extremity injuries between high school baseball pitchers who also played catcher as a secondary position and those who did not play catcher.

DESIGN

  Prospective cohort study.

SETTING

  Field laboratory.

PATIENTS OR OTHER PARTICIPANTS

  A total of 384 male high school baseball pitchers were recruited from 51 high school teams. Pitchers who reported their secondary position as catcher were classified into the pitcher/catcher group and those who did not report playing catcher as a secondary position were classified into the other group.

MAIN OUTCOME MEASURE(S)

  Participants completed a demographic questionnaire preseason and then athlete participation and injury status were tracked during the subsequent season. Athlete-exposures were monitored and the shoulder and elbow injury proportion rates were calculated.

RESULTS

  Athlete-exposures did not differ between groups ( P = .488). The pitcher/catcher group's risk of shoulder or elbow injury was 2.9 times greater than that of the other pitchers (15% versus 5%; injury proportion rate = 2.9; 95% confidence interval = 1.03, 8.12).

CONCLUSIONS

  Pitchers who reported also playing catcher were at a greater risk of sustaining a throwing-related shoulder or elbow injury than the other pitchers. These findings suggest that pitchers should consider not playing catcher as their secondary position in order to allow adequate time for recovery and to decrease their overall throwing load. Serial physical examinations of pitchers/catchers during the season may be useful in determining if their physical characteristics are changing during the season because of the cumulative throwing load.

Evidence-based rehabilitation of athletes with glenohumeral instability

PURPOSE

To give an overview of current knowledge and guidelines with respect to evidence-based rehabilitation of athletes with glenohumeral instability.

METHODS

This narrative review combines scientific evidence with clinical guidelines based on the current literature to highlight the different components of the rehabilitation of glenohumeral instability.

RESULTS

Depending on the specific characteristics of the instability pattern, the severity, recurrence, and direction, the therapeutic approach may be adapted to the needs and demands of the athlete. In general, attention should go to (1) restoration of rotator cuff strength and inter-muscular balance, focusing on the eccentric capacity of the external rotators, (2) normalization of rotational range of motion with special attention to the internal rotation ROM, (3) optimization of the flexibility and muscle performance of the scapular muscles, and (4) gradually increasing the functional sport-specific load on the shoulder girdle. The functional kinetic chain should be implemented throughout all stages of the rehabilitation program. Return to play should be based on subjective assessment as well as objective measurements of ROM, strength, and function.

CONCLUSIONS

This paper summarizes evidence-based guidelines for treatment of glenohumeral instability. These guidelines may assist the clinician in the prevention and rehabilitation of the overhead athlete.

LEVEL OF EVIDENCE

Expert opinion, Level V.