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The Addition of Glenohumeral Adductor Coactivation to a Rotator Cuff Exercise Program for Rotator Cuff Tendinopathy: A Single-Blind Randomized Controlled Trial

Journal of Orthopaedic & Sports Physical Therapy

Published Online:February 28, 2019Volume49Issue3Pages126-135

https://www.jospt.org/doi/10.2519/jospt.2019.8240

Abstract

Background

Treatments for rotator cuff tendinopathy include rotator cuff muscle strengthening to promote better muscle recruitment in order to minimize subacromial narrowing during active movement. Glenohumeral adductor recruitment has also been shown to prevent such narrowing in asymptomatic individuals; therefore, adding glenohumeral adductor coactivation during rotator cuff strengthening could enhance the efficacy of rotator cuff strengthening. However, no study has explored its benefits.

Objectives

To compare the short-term efficacy of adding glenohumeral adductor coactivation to a rotator cuff–strengthening program to improve function, reduce symptoms, and increase acromiohumeral distance in adults with rotator cuff tendinopathy.

Methods

In this single-blind randomized controlled trial, 42 participants with rotator cuff tendinopathy were randomly assigned to 2 groups, one that received strengthening of the scapular and rotator cuff muscles or one that received rotator cuff strengthening plus coactivation with pectoralis major and latissimus dorsi recruitment. The daily programs were performed at home for 6 weeks, with supervised training and follow-up sessions. Functional limitations/symptoms (Disabilities of the Arm, Shoulder and Hand [DASH] questionnaire as the primary outcome, and the Western Ontario Rotator Cuff index), pain (visual analog scale), and acromiohumeral distance were measured at baseline, 3 weeks, and 6 weeks. Data were analyzed using a mixed-model analysis of variance.

Results

No significant group-by-time interaction was observed for the Disabilities of the Arm, Shoulder and Hand questionnaire, Western Ontario Rotator Cuff index, visual analog scale, and acromiohumeral distance (P≥.055). Significant time effects were obtained for the Western Ontario Rotator Cuff index and visual analog scale for pain with movement (P<.001).

Conclusion

The present findings show that adding glenohumeral adductor coactivation to a rotator cuff–strengthening program does not result in improved short-term efficacy in any of the measured outcomes. This study was registered with ClinicalTrials.gov (NCT02837848).

Level of Evidence

Therapy, level 1b. J Orthop Sports Phys Ther 2019;49(3):126–135. Epub 30 Nov 2018. doi:10.2519/jospt.2019.8240

Shoulder pain is one of the most common types of musculoskeletal pain syndromes in the general population,²⁷ with a prevalence rate estimated to be between 7% and 26% and an annual incidence rate between 0.9% and 2.5%.³¹ Among the multiple causes of shoulder pain, rotator cuff tendinopathy is the most common, accounting for 85% of painful shoulders.³⁸^,⁴⁵ Rotator cuff tendinopathy is a general diagnosis including subacromial impingement syndrome, tendinosis and partial tear of the rotator cuff, tendinosis of the long head of the biceps, and subacromial bursitis.³⁹ All these conditions may be the result of impingement of the subacromial soft tissues between the coracoacromial arch and the superior aspect of the humeral head when the arm is elevated.⁵^,³⁹

Lack of coordination or weakness of scapulothoracic and scapulohumeral muscles⁸^,⁹^,¹⁴ are the primary factors thought to lead to subacromial narrowing in individuals with symptomatic rotator cuff tendinopathy.⁴² More specifically, the inability of the scapular muscles to achieve superior rotation and posterior tilt,¹⁸^,³⁰ as well as the failure of rotator cuff muscles to counter the superior humeral head translation imposed by deltoid contraction, can lead to impingement of the subacromial soft tissues when performing overhead dynamic tasks.¹⁴^,²⁶^,⁴⁰ Aside from rotator cuff muscles, opposition of such superior humeral head translation can be achieved by the glenohumeral adductors (ie, pectoralis major and latissimus dorsi muscles), which act as humeral head depressors by means of the medioinferior vector created by the orientation of their tendons.²¹ Recruitment of the glenohumeral adductors has been shown to decrease subacromial narrowing in elevated arms in asymptomatic individuals²¹^,²⁵^,⁴³ and is thought to be a coping mechanism to decrease pain in individuals with rotator cuff tendinopathy.¹⁰^,¹³^,⁴³

Recent systematic reviews¹¹^,²⁹ and meta-analyses¹⁶^,²⁴ have concluded that rotator cuff and scapular strengthening exercises should be included in rehabilitation programs for individuals with rotator cuff tendinopathy.²^,³^,⁷^,¹⁵^,³² However, to our knowledge, the efficacy of adding glenohumeral adductor coactivation during rotator cuff–strengthening exercises has never been evaluated in patients with rotator cuff tendinopathy. Because recruitment of those muscles could prevent a decrease in subacromial space during arm elevation, it could potentially lead to improved exercise performance, earlier benefits, and better treatment outcomes compared to routine rotator cuff–strengthening exercises.

The aim of this randomized controlled trial (RCT) was to compare the short-term efficacy of adding pectoralis major and latissimus dorsi coactivation to a rotator cuff–strengthening exercise program to improve function, reduce pain, and increase acromiohumeral distance (AHD) in adults with rotator cuff tendinopathy. Our hypothesis was that participants in the group receiving rotator cuff–strengthening exercise plus pectoralis major and latissimus dorsi coactivation (RCEx-plus-coactivation) would demonstrate greater improvement in function and greater reduction in pain than those in the group that received rotator cuff–strengthening exercises alone (RCEx).

Methods

Study Design

This parallel, single-blind prospective RCT included 3 evaluation sessions (baseline, week 3, and week 6) and a 6-week home exercise program (including 2 supervised physical therapy sessions, at baseline and week 2). The primary outcome was the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire, while the secondary outcomes were the Western Ontario Rotator Cuff (WORC) index, a visual analog scale (VAS) for pain, and AHD at 0°, 30°, and 60° of abduction, measured by ultrasonography.

Participants

Individuals with rotator cuff pathology confirmed by an orthopaedic surgeon were consecutively screened for potential eligibility. All participants provided informed consent prior to enrollment. Inclusion criteria were as follows: (1) 18 to 65 years of age, (2) symptoms lasting longer than 1 month, (3) presence of a painful arc in active flexion or abduction, (4) presence of a positive Neer sign or Hawkins-Kennedy test, (5) presence of pain when resisting humeral external rotation or abduction, and (6) ability to speak English or French to provide informed consent and to complete the questionnaires. The combination of criteria 3, 4, and 5 has been shown to have a sensitivity of 0.75 (confidence interval [CI]: 0.54, 0.96), a specificity of 0.74 (CI: 0.61, 0.88), and a positive likelihood ratio of 2.93 (CI: 1.60, 5.36).³⁵ Exclusion criteria were (1) presence or history of a shoulder fracture on the affected side, (2) a magnetic resonance imaging diagnosis or clinical signs of a full-thickness rotator cuff tear (significant weakness with resisting external rotation and abduction movement, positive drop-arm test), (3) history of surgery on the affected shoulder, (4) presence of shoulder capsulitis (restriction of passive glenohumeral movement of at least 30% for 2 or more directions), (5) presence of shoulder osteoarthritis, rheumatoid arthritis, or a systemic inflammatory or neurologic condition, (6) history of traumatic shoulder instability (dislocation), and (7) administration of a corticosteroid injection in the affected shoulder within the past 6 weeks. The study protocol was approved by the Centre Hospitalier Universitaire de Sherbrooke Human Research Ethics Committee (2017-1404). This RCT was registered with ClinicalTrials.gov (NCT02837848). Data were collected at the Centre Hospitalier Universitaire de Sherbrooke's Research Center.

Randomization and Blinding

Participants were randomly assigned to the RCEx group or the RCEx-plus-coactivation group. Before the study began, an independent person created a randomized allocation list with a random-number generator (www.randomizer.org), using 7 blocks of 6 participants each. Allocations were sequentially numbered and placed in sealed and opaque envelopes to ensure concealed allocation. After participant enrollment was confirmed and baseline outcome assessments were completed by the evaluator, the envelope was opened by the physical rehabilitation therapist. Participants were instructed not to talk about their exercise program and were blinded to what the other program entailed. At the end of the protocol, participants were asked if they knew the other group program. The evaluator remained the same throughout the study and was blinded to participants' group allocation. A code was assigned to each participant, and the evaluation data sheet contained no information that allowed group allocations to be revealed. The physical therapist was not blinded to group assignments.

Intervention

After randomization, all participants received their exercise programs. At the first visit, education about rotator cuff tendinopathy physiopathology, postural advice, and activity modification recommendations were provided to both groups. The physical therapist then taught the participants the exercises based on their allocation to either the RCEx or RCEx-plus-coactivation group, corrected their performance, and answered questions as required. An appointment with the physical therapist was scheduled 2 weeks later to review, correct, and progress the exercises to the next intensity level when needed. This appointment was also necessary to ensure that the coactivation in the RCEx-plus-coactivation group was achieved during rotator cuff strengthening. A telephone call was scheduled 4 weeks after the start of each program to answer any questions the participants had about the exercises. Participants in the RCEx-plus-coactivation group were reminded about the proper procedures for achieving coactivation.

The exercise program included the same exercises for both groups, as well as the same progressions (APPENDICES A and B):

Serratus anterior–strengthening exercises: wall push-ups with press-outs (addition of scapular protraction) were initially prescribed. Participants then progressed to inclined push-ups with press-outs, and finally to horizontal push-ups with press-outs.
Trapezius-strengthening exercises: scapular retraction exercises were first taught in a standing position, with the arms slightly abducted. Participants subsequently performed the exercises with arms at 90° of scapular plane abduction while standing. The final exercise pose was a prone position, with arms at 90° of scapular plane abduction.
Glenohumeral-strengthening exercises: rotator cuff muscle strengthening was performed via external and internal rotation exercises, while standing with the arm beside the trunk. Exercises progressed using colored elastic bands, starting with the lightest-tension band (yellow) and followed by colored bands (red, blue) of increasing tension. Once participants could perform all repetitions without pain, they were instructed to continue the same progression with the shoulder at 30° of abduction and the elbow supported on a table. Once participants could perform 10 repetitions of these exercises without pain, glenohumeral flexor- and abductor-strengthening exercises were introduced.

These exercises were selected because their efficacy has been reported in the literature.¹

Participants in the RCEx-plus-coactivation group had to perform the glenohumeral exercises while recruiting the pectoralis major and latissimus dorsi muscles. To achieve this, voluntary recruitment of the pectoralis major and latissimus dorsi was taught prior to the demonstration of the glenohumeral exercises using visual feedback provided by electromyography (EMG) (FREEEMG; BTS SpA, Milan, Italy). For the pectoralis major, the electrode was positioned on the muscle belly of the sternal part, over the costochondral joint of the third rib. The electrode on the latissimus dorsi was positioned on the muscle belly, 1 cm under the inferior angle of the scapula. Electrode placements were based on previous literature,¹⁹ pretested and adjusted to minimize cross-talk contamination and maximize signals.

Once recruitment was correctly executed (50% of the maximum voluntary contraction signal), it had to be maintained while performing the glenohumeral exercises. This was confirmed by visualizing EMG signals during the exercise training session. During each appointment with the physical therapist (baseline and week 2), participants were evaluated on their capacity to achieve the exercises while performing coactivation. If needed, additional practice was performed with the physical therapist, using EMG, until the exercises were mastered. During the phone appointment (4 weeks), participants were reminded about the proper procedure for achieving coactivation.

Conversely, participants in the RCEx group were instructed not to recruit the pectoralis major and latissimus dorsi muscles (less than 15% of the maximum voluntary contraction signal). This was also confirmed by visualizing EMG signals during the training sessions (at baseline and week 2).

Therefore, the only difference between the 2 groups was that the RCEx-plus-coactivation group was asked to recruit the pectoralis major and latissimus dorsi muscles during the glenohumeral-strengthening exercises. The other 2 exercises (serratus anterior strengthening and trapezius strengthening) and the education on rotator cuff tendinopathy were exactly the same for both groups.

Exercise Parameters

The following exercise parameters were given (APPENDIX A): 3 sets of 10 repetitions of each exercise, once a day and 7 days a week, for 6 weeks. Participants progressed to the next level when they could perform 3 sets of 10 repetitions without pain. Otherwise, if participants had pain of more than 4 on a 0-to-10 numeric pain-rating scale during the exercises, then they had to return to the previous exercise level. Participants were allowed to ice the shoulder. Participants were asked to complete a log book to document exercise compliance. All log books were returned to the evaluator at week 6.

Outcomes

Outcomes were assessed at 0, 3, and 6 weeks. After enrollment, participants were asked to complete a questionnaire on personal (ie, age, sex, and dominant side) and occupational variables (type of work). The primary outcome, the DASH questionnaire, is a 30-item self-reported questionnaire measuring symptoms and disabilities caused by a nonspecific upper-limb disorder. The questionnaire is scored on a 100-point scale, where 0 represents no disabilities and 100 represents extreme disabilities (minimal clinically important difference [MCID], 13 points).⁴⁷

Secondary outcomes included the WORC index, VAS, and AHD. The WORC index was also used to assess functional limitations. It is a disease-specific questionnaire developed to measure health-related function and quality of life of individuals with rotator cuff disorders. It contains 21 items and is scored out of 100, with 0 representing extreme function loss and 100 no function loss (MCID, 11 points).¹⁷ Pain at rest and during movement was evaluated using a 100-mm VAS, where 0 mm corresponds to no pain and 100 mm corresponds to the worst imaginable pain (MCID, 14.0 mm).⁴⁴

Finally, AHD was measured using an Aplio 50 (Toshiba Corporation, Tokyo, Japan) ultrasound scanner with a 7.5-Hz linear probe. Measurements were taken at 0°, 30°, and 60° of glenohumeral active abduction, in a sitting position. The probe was oriented along the longitudinal axis of the humerus on the anterior aspect of the lateral surface of the acromion.⁴¹ The AHD is defined as the tangential distance between the humeral head and the inferior edge of the acromion.¹² Measuring AHD with ultrasonography has been shown to be reliable (intraclass correlation coefficient [ICC]>0.90),⁴¹ with a minimal detectable change of 1.2 mm.³³

Sample Size

The sample size was estimated for the primary outcome, the DASH questionnaire, using the following parameters: (1) an MCID of 13 points,⁴⁷ (2) an SD of 14%,³⁴ (3) a statistical power of 0.80, (4) an alpha error of .05, (5) a 15% loss to follow-up, and (6) a unilateral hypothesis. The sample size required was 21 participants per group.

Analysis

Intention-to-treat (missing data handled using the average imputation method) and per-protocol analyses were performed for all outcomes. Two-way mixed analyses of variance (ANOVAs), assessing group (RCEx, RCEx-plus-coactivation) by time (baseline, week 3, week 6), were used to determine the added effects of coactivation on DASH, WORC, and VAS scores. A 3-way mixed ANOVA assessing group (RCEx, RCEx-plus-coactivation) by time (baseline, week 3, week 6) by angle (0°, 30°, 60° of abduction) was used to determine the effect of adding coactivation on AHD. Effect sizes were also reported using partial eta-square. Finally, for the DASH, WORC, and VAS, a chi-square test was used to compare the proportion of participants in each group with a clinically important improvement at 6 weeks. The level of significance was P<.05. Data were analyzed with SPSS Statistics Version 23 (IBM Corporation, Armonk, NY).

Results

From August 2016 to November 2017, 42 consecutive participants with rotator cuff tendinopathy were included from 121 potential candidates. Participant characteristics for each group at baseline are summarized in TABLE 1. Of the 42 participants, 3 did not complete the study (FIGURE 1): 1 withdrew due to the onset of another health condition requiring immediate medical intervention, 1 opted out because of the loss of a family member, and 1 declined further intervention because he was satisfied with the relief of symptoms and did not want to complete the study. Two were in the RCEx group, while the other was in the RCEx-plus-coactivation group.

TABLE 1 Participant Characteristics and Dependent Variables at Baseline*
Variable	RCEx Group (n = 21)	RCEx-Plus-Coactivation Group (n = 21)
Age, y	49.6 ± 13.2	50.2 ± 10.9
Sex, n
Female	13	9
Male	8	12
Dominance (right handed), n (%)	17 (81.0)	17 (81.0)
Symptom duration, mo	41.8 ± 40.5	44.2 ± 52.9
DASH, %	31.4 ± 15.9	31.9 ± 15.5
WORC, %	49.7 ± 19.3	51.0 ± 18.8
Pain at rest (VAS), mm	11.4 ± 14.0	16.2 ± 18.5
Pain with movement (VAS), mm	78.4 ± 15.2	72.1 ± 18.1
AHD at 0°, mm	11.0 ± 2.7	10.8 ± 2.1
AHD at 30°, mm	10.6 ± 3.4	10.3 ± 2.3
AHD at 60°, mm	9.7 ± 3.7	9.5 ± 2.7
Medication use at enrollment, n (%)^†	21 (100.0)	19 (90.5)

Abbreviations: AHD, acromiohumeral distance; DASH, Disabilities of the Arm, Shoulder and Hand questionnaire; RCEx, rotator cuff exercise; VAS, visual analog scale; WORC, Western Ontario Rotator Cuff index.

*Values are mean ± SD unless otherwise indicated.

^†Medication reported includes analgesics or nonsteroidal anti-inflammatory drugs.

**FIGURE 1.** Flow diagram for participant recruitment, allocation, and analysis.

At the end of the intervention, all participants did not know the intervention received by the other group. The assessor declared that group allocation was not known by any of the participants. According to the log book, the compliance rate was 85.7% and not different between groups (TABLE 2). Two participants per group experienced an increased pain level at 3 weeks or 6 weeks, which was addressed with corticosteroid injections or an alternative exercise program at the 6-week assessment. Mean scores at all measurement times, within-group changes from baseline at 3 weeks and 6 weeks, and between-group differences are presented in TABLE 3 (DASH, WORC, and VAS) and TABLE 4 (AHD at 0°, 30°, and 60° of abduction). No difference was shown between the groups regarding medication use at 6 weeks (RCEx, 13/21 [61.9%] versus RCEx-plus-coactivation, 10/21 [47.6%]; P = .421). However, the type of medication was not recorded.

**TABLE 2 Exercise Program Compliance Rate**
Rate	RCEx Group (n = 21)*	RCEx-Plus-Coactivation Group (n = 21)*	P Value
7 times per week	13 (61.9)	14 (66.7)	0.747
5–7 times per week	18 (85.7)	18 (85.7)	1.000
<5 times per week^†	3 (14.3)	3 (14.3)	1.000

Abbreviation: RCEx, rotator cuff exercise.

*Values are n (percent).

^†Includes loss to follow-up.

TABLE 3 DASH, WORC, and VAS Scores at Baseline, 3 Weeks, and 6 Weeks, and Within-Group Change From Baseline to 3 Weeks and 6 Weeks*
	Unadjusted Scores		Adjusted Scores^†
Outcome/Time	RCEx Group	RCEx-Plus-Coactivation Group	RCEx Group	RCEx-Plus-Coactivation Group	Between-Group Difference	P Value^‡
DASH^§						.742
Baseline	31.4 ± 15.9	31.9 ± 15.5	31.8 ± 13.4	32.2 ± 15.4
3 wk	31.0 ± 18.9	29.0 ± 17.6	31.0 ± 17.9	28.9 ± 17.1
Change (3 wk – baseline)			−0.8 (−4.6, 6.2)	−3.3 (−10.3, 3.8)	2.4 (−4.4, 9.3)
6 wk	29.9 ± 21.2	27.8 ± 19.2	29.9 ± 20.1	27.8 ± 18.7
Change (6 wk – baseline)			−2.0 (−10.4, 6.4)	−4.4 (−11.8, 2.9)	2.4 (−6.2, 11.1)
Time effect (η²)			0.014	0.079
WORC^‖						.754
Baseline	49.7 ± 19.3	51.0 ± 18.8	50.9 ± 16.5	51.6 ± 18.5
3 wk	59.7 ± 22.4	60.7 ± 23.5	59.7 ± 20.7	60.7 ± 22.9
Change (3 wk – baseline)			8.8 (−2.7, 20.3)	9.1 (3.5, 14.6)	−0.2 (−10.1, 9.7)
6 wk	61.6 ± 28.5	65.7 ± 26.5	61.7 ± 27.1	65.7 ± 25.8
Change (6 wk – baseline)			10.7 (−3.7, 25.2)	14.1 (5.3, 22.8)	−3.3 (−16.4, 9.7)
Time effect (η²)			0.132	0.398
Pain at rest (VAS, 0–100 mm)^¶					.244
Baseline	11.4 ± 14.0	16.2 ± 18.5	11.9 ± 13.9	14.5 ± 16.6
3 wk	21.0 ± 21.7	14.8 ± 15.8	21.0 ± 20.6	14.8 ± 15.4
Change (3 wk – baseline)			9.1 (−0.7, 18.8)	0.3 (−11.0, 11.4)	8.8 (−2.7, 20.3)
6 wk	19.6 ± 24.5	15.8 ± 21.1	19.6 ± 23.1	15.8 ± 20.5
Change (6 wk – baseline)			7.7 (−3.5, 18.9)	1.3 (−7.5, 11.2)	6.4 (−5.1, 18.0)
Time effect (η²)			0.142	0.003
Pain with movement (VAS, 0–100 mm)^¶					.417
Baseline	78.4 ± 15.2	72.1 ± 18.1	78.0 ± 14.2	71.1 ± 17.3
3 wk	60.3 ± 23.0	55.7 ± 24.2	60.2 ± 21.8	55.7 ± 23.6
Change (3 wk – baseline)			−17.8 (−33.0, −2.6)	−15.3 (−25.4, −5.3)	−2.4 (−16.5, 11.7)
6 wk	53.7 ± 24.6	56.1 ± 30.4	53.7 ± 23.4	56.1 ± 29.6
Change (6 wk – baseline)			−24.3 (−37.6, −11.1)	−15.0 (−30.5, 0.5)	−9.3 (−25.1, 6.4)
Time effect (η²)			0.378	0.221

Abbreviations: DASH, Disabilities of the Arm, Shoulder and Hand questionnaire; RCEx, rotator cuff exercise; VAS, visual analog scale; WORC, Western Ontario Rotator Cuff index.

*Outcome values at each point are mean ± SD, and values for change scores are mean (95% confidence interval).

^†Adjusted values from mixed-model analyses, with average imputation for missing values.

^‡Time-by-group interaction effect.

^§Scale is from 0 to 100, where 0 is no disability.

^‖Scale is from 0 to 100, where 100 is no functional loss.

^·Scale is from 0 to 100 mm, where 0 is no pain.

TABLE 4 AHD at 0°, 30°, and 60° at Baseline, 3 Weeks, and 6 Weeks, and Within-Group Change From Baseline at 3 Weeks and 6 Weeks*
	Unadjusted Scores		Adjusted Scores^†
Outcome/Time	RCEx Group	RCEx-Plus-Coactivation Group	RCEx Group	RCEx-Plus-Coactivation Group	Between-Group Difference	P Value
AHD at 0°, mm						.096^‡
Baseline	11.0 ± 2.7	10.8 ± 2.1	10.9 ± 2.5	10.8 ± 2.1
3 wk	10.1 ± 1.4	11.2 ± 2.1	10.1 ± 1.2	11.2 ± 2.0
Change (3 wk – baseline)			−0.8 (−2.1, 0.6)	0.4 (−0.7, 1.5)	−1.2 (−2.5, 0.2)
6 wk	10.4 ± 1.9	11.5 ± 2.8	10.5 ± 1.8	11.5 ± 2.7
Change (6 wk – baseline)			−0.4 (−1.4, 0.5)	0.7 (−0.7, 2.0)	−1.1 (−2.4, 0.2)
Time effect (η²)			0.080	0.059
AHD at 30°, mm						.276^‡
Baseline	10.6 ± 3.4	10.3 ± 2.3	10.5 ± 3.0	10.4 ± 2.3
3 wk	10.2 ± 2.5	10.8 ± 2.8	10.2 ± 2.2	10.8 ± 2.7
Change (3 wk – baseline)			−0.3 (−1.1, 0.5)	0.5 (−0.6, 1.5)	−0.8 (−1.8, 0.3)
6 wk	9.9 ± 2.0	10.6 ± 2.4	9.9 ± 1.9	10.6 ± 2.4
Change (6 wk – baseline)			−0.6 (−1.9, 0.7)	0.2 (−0.7, 1.2)	−0.8 (−2.1, 0.4)
Time effect (η²)			0.050	0.035
AHD at 60°, mm						.055^‡
Baseline	9.7 ± 3.7	9.5 ± 2.7	9.8 ± 3.5	9.5 ± 2.7
3 wk	8.2 ± 1.4	9.9 ± 2.8	8.1 ± 1.2	9.9 ± 2.7
Change (3 wk – baseline)			−1.7 (−3.3, 0.0)	0.4 (−0.4, 1.3)	−2.1 (−3.6, 0.7)
6 wk	9.5 ± 2.8	9.8 ± 2.5	9.5 ± 2.6	9.8 ± 2.4
Change (6 wk – baseline)			−0.3 (−1.6, 0.9)	0.3 (−0.8, 1.5)	−0.6 (−1.9, 0.7)
Time effect (η²)			0.214	0.026
Effect						.102^§

Abbreviations: AHD, acromiohumeral distance; RCEx, rotator cuff exercise.

*Outcome values at each point are mean ± SD, and values for change scores are mean (95% confidence interval).

^†Adjusted values from mixed-model analyses, with average imputation for missing values.

^‡Time-by-group interaction effect.

^§Time-by-group-by-angle interaction effect.

For the primary outcome measure (DASH questionnaire), intention-to-treat and per-protocol analyses showed no significant time-by-group interaction (P = .742, P = .755) (FIGURE 2), and no time (P>.211) or group (P>.796) effect. No statistically significant difference was obtained for the proportion of participants in each group with a clinically important improvement on the DASH questionnaire at 6 weeks (RCEx, 4/19 [21.1%] versus RCEx-plus-coactivation, 6/20 [30.0%]; P = .522).

**FIGURE 2.** Scores on the DASH for the RCEx group (n = 21) and the RCEx-plus-coactivation group (n = 21) at baseline, 3 weeks, and at the end of the intervention (6 weeks). Values are mean ± SD DASH score (0–100 points). Abbreviations: DASH, Disabilities of the Arm, Shoulder and Hand questionnaire; RCEx, rotator cuff exercise.

Similarly for the WORC index, intention-to-treat and per-protocol analyses showed no significant time-by-group interaction (P>.754) (FIGURE 3) or group effect (P>.755), but did show a significant time effect (P<.001). The mean WORC score improved from baseline to week 3 (P = .010) and was not statistically significant between weeks 3 and 6 (P = .075). No statistically significant difference was obtained for the proportion of participants in each group with a clinically important improvement on the WORC index at 6 weeks (RCEx, 8/19 [42.1%] versus RCEx-plus-coactivation, 11/20 [55.0%]; P = .421).

**FIGURE 3.** Scores on the WORC for the RCEx group (n = 21) and the RCEx-plus-coactivation group (n = 21) at baseline, 3 weeks, and at the end of the intervention (6 weeks). Values are mean ± SD WORC score (0–100 points). Abbreviations: RCEx, rotator cuff exercise; WORC, Western Ontario Rotator Cuff index.

Intention-to-treat and per-protocol ANOVAs showed no significant time-by-group interaction or group effect for pain at rest (P>.244) (FIGURE 4) or pain with movement (P = .260) (FIGURE 5). No significant time effect was observed for pain at rest (P>.152), whereas a significant time effect was found for pain with movement (P<.001). The mean score for pain with movement improved from baseline to week 3 (P<.001) and was not statistically significant between weeks 3 and 6 (P = .990). The proportion of participants with a clinically important improvement for pain at rest (RCEx, 3/19 [15.8%] versus RCEx-plus-coactivation, 3/20 [15.0%]; P = .946) and pain with movement (RCEx, 13/19 [68.4%] versus RCEx-plus-coactivation, 9/20 [45.0%]; P = .140) was not significantly different between groups.

**FIGURE 4.** Scores on the pain VAS at rest for the RCEx group (n = 21) and the RCEx-plus-coactivation group (n = 21) at baseline, 3 weeks, and at the end of the intervention (6 weeks). Values are mean ± SD VAS score (0–100 mm). Abbreviations: RCEx, rotator cuff exercise; VAS, visual analog scale.

**FIGURE 5.** Scores on the pain VAS with movement for the RCEx group (n = 21) and the RCEx-plus-coactivation group (n = 21) at baseline, 3 weeks, and at the end of the intervention (6 weeks). Values are mean ± SD VAS score (0–100 mm). Abbreviations: RCEx, rotator cuff exercise; VAS, visual analog scale.

Intention-to-treat and per-protocol analyses of AHD showed no significant group-by-time-by-angle (P>.102) or group-by-time (P>.055) interaction for all angles. However, a main angle effect (P<.001) was observed, showing that the AHD decreased as the arm was abducted (FIGURE 6). For all participants, the decrease in AHD was significant between 0° and 30° (P<.001) and between 30° and 60° (P<.001). However, a narrowing (mean change, −1.4 mm; 95% CI: −1.8, −0.8 mm) greater than the AHD minimal detectable change was only observed between 0° and 60° (P<.001).

**FIGURE 6.** Measures of AHD for the RCEx group (n = 21), the RCEx-plus-coactivation group (n = 21), and all participants (n = 42) at 0°, 30°, and 60° of abduction. Values are mean ± SD AHD (millimeters). Abbreviations: AHD, acromiohumeral distance; RCEx, rotator cuff exercise.

Discussion

The present findings suggest that the addition of glenohumeral adductor coactivation to regular rotator cuff–strengthening exercises does not result in additional benefits, as similar changes were observed in both groups. To our knowledge, this is the first RCT to evaluate the effect of adding coactivation during strengthening exercises in individuals with rotator cuff tendinopathy. Only Beaudreuil et al²^,³ have assessed the effect of coactivation on passive and active abduction movements. They compared the coactivation approach with a nonspecific mobilization exercise program and concluded that coactivation was more effective in reducing pain but was not more effective in improving function. The present study assessed the coactivation approach in a strengthening context, targeting the principal deficiencies observed in patients with rotator cuff tendinopathy. Unlike Beaudreuil et al,²^,³ our results do not support the addition of coactivation to a rotator cuff–strengthening program to improve function and reduce pain in individuals with rotator cuff tendinopathy.

The clinical reasoning for adding glenohumeral coactivation to a regular rotator cuff–strengthening program was based on the depressor effect on the humeral head.²⁰^,²⁵^,⁴³ Our findings, however, show no additional effect of EMG-guided coactivation. Both programs also resulted in smaller changes in symptoms and functional limitations than previously observed in clinical trials that have looked at the effect of scapular and rotator cuff strengthening in individuals with rotator cuff tendinopathy.¹^,²⁴ Improvements much lower than the DASH MCID (13 points)⁴⁷ and close to the WORC MCID (11 points)¹⁷ and the VAS MCID (14.0 mm)⁴⁴ were observed. These small changes could be explained by the fact that the mean symptom duration for participants in the present study was more than 3 years, which is almost twice the time reported in most of the published studies.¹^,¹⁶ A systematic review published by Kuijpers et al²⁸ presented the different prognostic factors associated with poorer outcomes in individuals with shoulder disorders. The authors concluded that there is moderate evidence that a long duration of complaints predicts poorer outcomes. This could explain the lower improvement in function and the smaller decrease in pain observed in the present study.

Moreover, patients with rotator cuff tendinopathy represent a heterogeneous population, as many factors have been linked to its physiopathology.⁴² This multifactorial etiology includes factors that are intrinsic (eg, age, vascularity, altered mechanical properties),⁴^,⁴⁶ extrinsic (eg, anatomical factors, muscle deficits, soft tissue tightness),⁶^,²⁶ and neurophysiological (eg, sensitization of pain pathways, decreased corticospinal excitability).²³^,³⁷ Thus, the fact that the exercise programs in this study mainly targeted rotator cuff and scapular weakness and were not specific to the particular deficiencies of each participant could be another factor that explains the magnitude of changes following the strengthening programs.⁴¹

Finally, only 1 training session, 1 follow-up session (2 weeks), and 1 phone appointment (4 weeks) were scheduled over the 6-week program. Even if home exercise programs have been shown to be as effective as supervised exercises,²² the small number of training sessions, as well as the pain intensity (4/10) allowed during strengthening exercises, could have resulted in inadequate dosing, which could also explain the low efficacy of the programs.

Interventions used to rehabilitate rotator cuff tendinopathy often target the principal deficiencies thought to decrease the subacromial space.²⁴^,²⁹ However, even if significant improvements were observed on the WORC index and VAS for pain with movement in the present study, no significant changes were observed in AHD at 30° and 60° of active abduction. Although weakness of rotator cuff and scapular muscles has been linked to rotator cuff tendinopathy, a loss of motor control (activation or coordination) of these muscles is thought to have a greater influence on AHD during dynamic movement.⁸^,⁹^,³⁶^,⁴² Thus, our programs did not address motor control of those muscles. A stronger muscle will not necessarily be recruited at the right time during active movement. It would have been interesting to add such exercises in the present study, as previous studies that included motor control exercises showed greater improvement in functional limitations and pain⁴¹^,⁴⁸ and an increase in AHD.⁴¹

There are some limitations associated with the present study. First, changes were made to the protocol in terms of outcome measurement times, whereas data were collected only up to 6 weeks. The RCT registration stated that data would be collected until 24 weeks. However, our hypothesis was that adding coactivation would result in improved exercise performance, earlier benefits, and better outcomes. Because no differences were observed over the short term (3 and 6 weeks), we decided to stop data collection at 6 weeks. Previous literature comparing different types of exercises for rotator cuff tendinopathy has reported that most changes and differences occur within the first weeks of the intervention.⁷^,¹⁵^,³² Nevertheless, further gains might have been observed had the exercises been continued over the long term.

Second, although meticulous attention was given to the training and application of coactivation over the course of the intervention, we cannot exclude the possibility that some participants in the RCEx-plus-coactivation group might not have performed the coactivation at home.

Finally, the physical therapist was not blinded to the participants' allocation group, and the participants were not blinded to their allocation group. However, we did make attempts to ensure blinding by instructing participants not to talk about their exercise program.

Conclusion

The results of this study show no benefit of adding glenohumeral adductor coactivation to rotator cuff–strengthening exercises to improve function, decrease pain, and increase AHD after a 6-week exercise program. Both groups achieved similar improvements on the WORC index and on the VAS for pain with movement, while no change was observed in scores on the DASH questionnaire, VAS for pain at rest, and AHD. Further studies could identify characteristics of patients who might respond well to exercises, and characteristics of those who would more likely benefit from another intervention.

Key Points

Findings

Adding glenohumeral adductor coactivation to regular rotator cuff strengthening did not result in additional benefits.

Implications

For rotator cuff tendinopathy, adding glenohumeral adductor coactivation, to increase subacromial space, to rotator cuff–strengthening exercise is no more effective than rotator cuff–strengthening exercise alone.

Caution

This study only provided data within the first 6 weeks of treatment. No conclusion can be made in terms of long-term efficacy.

Acknowledgments

The authors thank the Centre Hospitalier Universitaire de Sherbrooke's orthopaedic research team and the Clinique Universitaire de Readaptation de l'Estrie for their assistance with this study.

References

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Appendix A

Consensus on Exercise Reporting Template*
Item Category	Item	Abbreviated Item Description
WHAT: materials	1	Type of exercise equipment: resistive band (yellow, red, blue)
WHO: provider	2	Qualifications of the exercise instructor: physical rehabilitation therapist (Quebec physical therapist assistant)
HOW: delivery	3	Whether exercises are performed individually or in a group: individually
	4	Whether exercises are supervised or unsupervised: supervised during training sessions (baseline and week 2), unsupervised for home exercises
	5	Measurement and reporting of adherence to exercise: participants wrote down in a log book how many times a week the prescribed exercises were performed
	6	Details of motivation strategies: patient education about the importance of doing the exercises
	7	Decision rules for progressing the exercise program: participants progressed to the next level when they could perform 3 sets of 10 repetitions without pain. Otherwise, if participants had pain of more than 4 on a 0-to-10 numeric pain-rating scale during the exercises, then they had to drop down to the previous level of exercise
	8	Each exercise is described so that it can be replicated (eg, illustrations, photographs): figures and instructions of all the strengthening exercises performed were given to each participant (see APPENDIX B)
	9	Content of any home program component: serratus anterior, trapezius, and rotator cuff strengthening
	10	Nonexercise components: at the first visit, education about rotator cuff tendinopathy physiopathology, postural advice, and activity-modification recommendations were provided
	11	How adverse events that occur during exercise are documented and managed: documented in the log book and managed at the 6-week assessment with alternative exercise programs or corticosteroid injection
WHERE: location	12	Setting in which exercises are performed: supervised during the training session with electromyographic electrodes on participants (local physical therapy at research center), unsupervised at participant's home
WHEN, HOW MUCH: dosage	13	Detailed description of the exercises (eg, sets, repetitions, duration, intensity): 3 sets of 10 repetitions, once a day, 7 days a week, 6 weeks
TAILORING: what, how	14	Whether exercises are generic (“one size fits all”) or tailored to the individual: tailored to the individual regarding pain intensity and difficulty to perform exercises
	15	Decision rule that determines the starting level for exercise: based on the analysis of the therapist about each participant (level of pain at rest and with movement, quality of exercise performance)
HOW WELL: planned, actual	16	Whether the exercise intervention is delivered and performed as planned: exercises were learned and practiced during the training session and performed at home. The exercises were revised at the 2-week appointment and adjusted according to performance. Progression was taught and demonstrated according to item 7

*Adapted from Slade SC, Dionne CE, Underwood M, et al. Consensus on Exercise Reporting Template (CERT): modified Delphi study. Phys Ther. 2016;96:1514–1524. https://doi.org/10.2522/ptj.20150668 by permission of the American Physical Therapy Association.

Appendix B

**Guideline for Strengthening Exercises**
Exercise	Description	Illustration
Serratus anterior	1. In standing position, the participant was asked to perform wall push-ups with press-outs (addition of scapular protraction)	Download Figure Download PowerPoint
	2. In inclined position, the participant was asked to perform push-ups with press-outs (addition of scapular protraction)	Download Figure Download PowerPoint
	3. In prone position, the participant was asked to perform push-ups with press-outs (addition of scapular protraction)	Download Figure Download PowerPoint
Trapezius	1. In standing position, with the arms slightly abducted, the participant was asked to perform a scapular retraction	Download Figure Download PowerPoint
	2. In standing position, with arms at 90° of the scapular plane, the participant was asked to perform a scapular retraction	Download Figure Download PowerPoint
	3. In prone position, with arms at 90° of the scapular plane, the participant was asked to perform a scapular retraction	Download Figure Download PowerPoint
External rotator muscles	1. In standing position with the arm beside the trunk, the participant was asked to perform an external rotation	Download Figure Download PowerPoint
	2. In sitting position with the arm abducted at 30° and the elbow supported, the participant was asked to perform an external rotation	Download Figure Download PowerPoint
Internal rotator muscles	1. In standing position with the arm beside the trunk, the participant was asked to perform an internal rotation	Download Figure Download PowerPoint
	2. In sitting position with the arm abducted at 30° and the elbow supported, the participant was asked to perform an internal rotation	Download Figure Download PowerPoint
Flexor muscles	1. In standing position, the participant was asked to perform flexion	Download Figure Download PowerPoint
Abductor muscles	1. In standing position, the participant was asked to perform abduction	Download Figure Download PowerPoint

Volume 49, Issue 3March 2019

Pages: 117-210

Keywords

Correspondence

Address correspondence to Nicolas Boudreau, Faculty of Medicine and Health Sciences, University of Sherbrooke, 3001 12th Avenue North, Sherbrooke, QC, Canada J1H 5N4. E-mail: [email protected]

Disclosure

This study received approval from the Centre Hospitalier Universitaire de Sherbrooke's Human Research Ethics Committee (2017-1404). It is registered with ClinicalTrials.gov (NCT02837848). Funding was granted by the Ordre professionnel de la Physiothérapie du Québec and Réseau Provincial de Recherche en Adaptation-Réadaptation. Mr Boudreau is also supported by Fonds de Recherche du Québec-Santé. The authors certify that they have no affiliations with or financial involvement in any organization or entity with a direct financial interest in the subject matter or materials discussed in the article.

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The Addition of Glenohumeral Adductor Coactivation to a Rotator Cuff Exercise Program for Rotator Cuff Tendinopathy: A Single-Blind Randomized Controlled Trial

Abstract

Background

Objectives

Methods

Results

Conclusion

Level of Evidence