PERCEIVED SELF-REPORT OF EFFORT DURING ROTATOR CUFF & SCAPULAR REHABILITATIVE EXERCISE IN PATIENTS AFTER SHOULDER SURGERY

Abstract

Background:

Rehabilitation following shoulder surgery involves the use of resistive exercise but dosing of these ­exercises historically employs multiple sets of pre-determined repetitions and few reports document the perceived effort encountered by patients during these exercises for both elastic resistance and free-weights. The OMNI-Resistance Exercise Scale (OMNI-RES) has been tested and applied as a measure of perceived exertion (RPE) for resistive exercise but has not gained widespread acceptance as an optimal method for physical therapists to document RPE during rehabilitation of shoulder surgery.

Purpose:

To generate descriptive values of RPE encountered during common shoulder exercises of varying resistance in patients following shoulder surgery as well as provide a comparative analysis between perceived exertion ratings of similar exercise movement patterns using elastic and traditional isotonic resistance.

Study Design:

Descriptive Cross-sectional Cohort

Methods:

Sixty-six subjects (mean age 53.3 + 12.8 years) were included in this study following shoulder surgery (RC repair n=22, labral repair n=10, SA n=34). Perceived exertion using the OMNI-RES was recorded during performance of seven rotator cuff and scapular rehabilitation exercises at 6- and 12-weeks following surgery.

Results:

Mean RPE using OMNI-RES in combined surgical groups ranged between 3.6 and 5.7 (mean = 4.50 + 2.1) across all seven exercises (scale 0 = very easy to 10 = extremely hard). From the external rotation (ER) exercise pair, paired t-tests revealed standing ER w/ Thera-band® (ERB) had a significantly higher OMNI-RES score versus sidelying ER w/ cuff weight (SLERW) (mean: 5.13 vs 4.41, p = 0.001) while the extension exercise pair consisting of standing shoulder extension w/ band (EXTB) and prone extension w/ cuff weight (PEXTW) showed no significant difference in OMNI-RES score (mean: 3.54, 3.67, p = 0.626).

Conclusion:

Commonly prescribed resistance exercise in the rehabilitation following shoulder surgery show light-moderate ratings of perceived exertion at both 6 & 12 week post-operative timepoints across three surgical procedures.

Level of Evidence:

3b

INTRODUCTION

Musculoskeletal disorders of the shoulder complex are common reasons to seek both non-operative and surgical medical care. It is estimated that over 270,000 rotator cuff (RC) repairs were performed in the United States in 2006 and the incidence of RC repair is rising.^1,2 Also, anterior shoulder instability is common,³ and patient outcomes may be improved following surgical stabilization via labral repair versus non-operative management.^4,5 Additionally, shoulder arthroplasty (SA) is being increasingly selected in recent decades for patients with shoulder osteoarthritis.⁶ Following surgery, therapists use varying post-operative protocols to manage symptoms, restore range of motion, and improve shoulder and scapular muscle strength and endurance.^7-10 While rotator cuff strength has been shown to gradually improve within the first post-operative year,¹¹ there are no widespread, clinically accepted dosage parameters for resistive exercise. Given potentially high RC re-tear rates following repair,¹² recent literature has focused on the timing of exercise introduction in efforts to maximize clinical outcomes.^13,14 There has been little focus on the optimal dosing of resistive exercises and programs are often standardized to a specific exercise volume with variable consideration of patient subjective report and exercise intensity. A review of therapeutic exercise for rotator cuff tendinopathy concluded that pain and/or fatigue can be used to successfully guide rehabilitation programs but specific recommendations for acceptable levels of fatigue were not reported as only two of the fourteen articles reviewed mentioned fatigue levels as a guide for exercise.¹⁵

Rating of perceived exertion (RPE) scales are widely used as a way of monitoring and tracking exercise intensity. Previous literature has suggested a positive linear relationship between exercise intensity levels and ratings of perceived exertion during bouts of resistive training.^16-20 The OMNI-Resistance exercise scale (OMNI-RES) has been developed to monitor RPE of both the overall body experience and active muscle groups for resistive exercise.¹⁷ The OMNI-RES is a 0-10 scale for use among males and females of all ages as a tool to control intensity of strength training. The OMNI-RES scale differs from other RPE scales, such as the Borg CR10 scale,²¹ by offering a resistance exercise-mode specific pictorial¹⁷ to assist participants rate tasks accurately. In a study to establish the instrument's concurrent validation, Robertson et al¹⁷ monitored total weight lifted, blood lactic acid concentration, and rating of perceived exertion for active muscles (RPE-AM) and overall body (RPE-O) using the OMNI-RES during weightlifting against the force of gravity.

Thera-band® (TB) resistance bands and tubing are commonly used in various postoperative shoulder rehabilitation protocols.^22,23 Colado et al²⁴ examined the construct and concurrent validity of the OMNI-RES scale for TB resisted shoulder lateral and frontal raise exercises (OMNI-RES EB). A new OMNI-RES diagram for use with elastic band exercises was developed which exchanged images of elastic bands with the weighted barbells seen on the original diagram. Correlations between RPE from the OMNI-RES EB and the TB RPE scale using regression analysis established construct validity reporting significant differences (p ≤ 0.05) in electromyography (EMG) activity, heart rate, and RPE scores between the high and low intensity sets of two separate exercises. Overall and active muscle RPE scale scores demonstrated intraclass correlation coefficient values of 0.67 and 0.58 respectively. Validity coefficients ranged from r²=0.76 to 0.85 for PRE-AM and r²=0.87 for RPE-O.

Based on the validation results, the OMNI-RES can be used to monitor exercise intensity using both isotonic weights and elastic resistance. For this study, the OMNI-RES was used postoperatively to track and generate descriptive RPE during seven commonly utilized exercises involving both free weights and TB elastic bands at 6 and 12 week postoperative time points. The purpose of the study was to generate descriptive values of RPE encountered during common shoulder exercises of varying resistance in patients following shoulder surgery as well as provide a comparative analysis between perceived exertion ratings of similar exercise movement patterns using elastic and traditional isotonic resistance

METHODS

Patients between the ages of 18 and 75 undergoing rehabilitation following RC and labral repair and SA were asked to volunteer to participate in this study. All post-surgical patients during the study period were given the opportunity to participate in the study. Patients were tested during their 6^th and 12^th post-operative weeks following RC and labral repair or SA. No minimal range of motion or strength requirements were required for inclusion in this study. Prior to involvement, all subjects signed an informed consent. This cross-sectional cohort study was reviewed and approved by the IRB of Physiotherapy Associates (Exton, PA). Standardized data collection forms were used to guide consistent acquisition of data from the patient during a designated rehabilitation session + 1 week from the 6^th and 12^th post-operative week of rehabilitation. All rehabilitation and data collection was performed at a single clinic, with patients from the lead author's caseload.

With the OMNI-RES placed in front of them in clear view, patients were asked, “How hard do you feel your muscles are working?” to estimate their overall muscular effort level after a series of designated exercises during one specific rehabilitation session in the 6^th and 12^th week following surgery. Exercises chosen for this research have been previously studied with EMG and are known to create moderate to high levels of activation of the rotator cuff and scapular musculature.^22,25-28 During these data acquisition sessions, exercises were performed in a randomized fashion using a random numerical generator to minimize the effects and possibility of a systematic bias from muscular fatigue in this investigation. Due to the advanced nature of certain exercises selected for this study, not all exercises were completed by all patients. Each participant's exercise routine was decided based on surgical procedure, post-operative time point, age, muscle strength, and functional goals. If appropriate, patients performed both exercises within an exercise pair. Table 1 lists the exercises studied in this investigation and the time point during which the subject was asked to rate the perceived exertion using the OMNI-RES. Repetition-based and time-based exercise were performed for two sets of fifteen repetitions and two sets of 30 seconds, respectively, during both standard follow-up visits and data collection sessions. The patient was asked to provide RPE immediately following completion of the exercise.

Table 1.

Rehabilitation Exercises and Timing of OMNI-RES Application.

1.Sidelying external rotation with cuff weight (SLERW), weight applied at the wrist. After 2nd set of 15 repetitions. 2.External rotation oscillation at 100% elongation with elastic resistance (EROB) with Thera-band® tubing. After 2nd set of 30 seconds. 3.External rotation with retraction with elastic resistance (ERRB) at 100% elongation with Thera-band® tubing. After 2nd set of 15 repetitions. 4.Prone extension with external humeral rotation with cuff weight (PEXTW), weight applied at the wrist. After 2nd set of 15 repetitions. 5.Prone horizontal abduction with external humeral rotation with cuff weight (PHABW), weight applied at the wrist. After 2nd set of 15 repetitions. 6.Standing external rotation with elastic resistance (ERB) at 100% elongation loading with Thera-band®. After 2nd set of 15 repetitions. 7.Standing extension with scapular retraction with elastic resistance (EXTB) at 100% elongation with Thera-band® tubing. After 2nd set of 15 repetitions.

Patients were tested at two time points during their rehabilitation following surgery using identical procedures during each data collection session. Collection was performed by one of two Physical Therapists or one Certified Athletic Trainer using common verbiage and procedures as outlined. The resistance level (cuff weight) and TB color used during each exercise was recorded by the examiner. Resistance levels for each exercise were selected using the resistance level that allowed the patient to perform the exercise without pain, and to perform the movement without compensation during all repetitions. The patient used the resistance levels from their prior session of rehabilitation during the testing sessions. To standardize resistance levels of the resistance bands during the testing procedure, markings on the floor were used to represent 100% elongation of the band. For shoulder extension, 100% elongation corresponded to the position of 45 degrees as pictured which was mid-way through the movement performed by the subject (Figure 1a). For external rotation, 100% elongation corresponded to the position of 45 degrees of internal rotation again approximately mid-way through the exercise range of motion (Figure 1b). This resulted in the desired band tension forces reported in Table 2.

Figure 1.

a) shoulder extension with elastic resistance, b) shoulder external rotation with elastic resistance, c) shoulder external rotation with elastic resistance and oscillation usingTheraband Flexbar, (Performance Health, Akron, OH, USA).

Table 2.

Thera-band® Resistance Progression.

Color	Resistance (lbs.)
Tan	2.4
Yellow	3.0
Red	3.7
Green	4.6

Adapted from Thera-band® Color Progression Resistance at 100% band Elongation

Statistical Methods

All data were entered into an Excel Spreadsheet and analyzed using SPSS (Chicago, IL). Descriptive statistics were generated and analyzed with comparison between select means performed for paired exercises (elastic resistance vs traditional isotonic cuff weight) using a paired t-test.

RESULTS

Sixty-six subjects participated in this study. Subjects mean age was 53.3 + 12.8 years. Ten subjects were status-post labral repair, 22 had arthroscopic RC repair, and 34 were status-post anatomic SA

Table 3 presents the mean OMNI-RES ratings from the seven exercises of 4.5 + 0.79 (Range 3.6-5.7) across all surgical groups at 6- and 12-week post-operative timepoints. Among this cohort, external rotation oscillation with TB (EROB) and standing extension with TB (EXTB) had the highest and lowest perceived exertion scores, respectively (OMNI RES: 5.7, 3.6). Across all surgical groups, OMNI-RES averages were similar in the 6-week and 12-week post-operative sub-groups (4.2 versus 4.6) with the average absolute mean difference (AMD) between individual exercises at 6 versus 12 weeks post-op found to be 0.5 (Table 4).

Table 3.

OMNI RES Scoring for all Exercises

Exercise	N	Minimum	Maximum	Mean	Std. Deviation
1. SLERW	66	0	9	4.3	2.2
2. EROB	45	1	10	5.7	2.3
3. ERRB	36	1	8	4.3	2.1
4. PEXTW	56	0	8	3.6	2.1
5. PHABW	29	2	8	4.8	1.8
6. ERB	64	1	10	5.1	2.3
7. EXTB	63	0	9	3.5	2.1
Average:	51	.7	8.9	4.5	2.1

N=Combined surgical groups of participants performing exercise across all post-operative timepoints.

Abbreviations: SLERW = sidelying ER w/ cuff weight, EROB = external rotation oscillation w/ band, ERRB = external rotation and retraction w/ band, PEXTW = prone extension w/ cuff weight, PHABW = prone horizontal abduction w/ cuff weight, ERB = external rotation w/ band, EXTB = extension w/ band

Table 4.

OMNI RES Scoring Averages at 6 and 12 weeks Post-op.

Exercise	6 Weeks				12 Weeks
	N	Mean	Std. Dev.	N	Mean	Std. Dev.	AMD
1. SLERW	33	4.4	2.2	33	4.3	2.2	.1
2. EROB	13	5.2	2.0	32	5.9	2.4	.7
3. ERRB	10	3.5	1.8	26	4.7	2.2	1.2
4. PEXTW	23	3.7	2.3	33	3.6	1.9	.1
5. PHABW	4	4.5	1.3	25	4.9	2.0	.4
6. ERB	31	4.8	2.2	33	5.4	2.3	.6
7. EXTB	31	3.3	2.0	32	3.7	2.2	.4
Average:	21	4.2	—	31	4.6	—	.5

N=Combined surgical groups of participants performing exercise at 6 and 12 weeks post-op

Abbreviations: AMD = Absolute Mean Difference (6 week mean – 12 week mean), Std. Dev. = standard deviation, SLERW = sidelying ER w/ cuff weight, EROB = external rotation oscillation w/ band, ERRB = external rotation and retraction w/ band, PEXTW = prone extension w/ cuff weight, PHABW = prone horizontal abduction w/ cuff weight, ERB = external rotation w/ band, EXTB = extension w/ band

Table 5 shows statistical results of comparisons between OMNI-RES ratings for common exercise pairings (external rotation: sidelying with cuff weight (SLERW), standing with elastic resistance (ERB); shoulder extension: prone extension with cuff weight (PEXTW), standing shoulder extension with elastic resistance (EXTB)). The shoulder external rotation exercise pair using either a cuff weight or TB (SLERW, ERB) was found to have significantly higher perceived exertion during ERB than SLERW (p = 0.001) while the shoulder extension exercise pair (PEXTW, EXTB) revealed no difference in perceived exertion (p = 0.626). Additionally, Table 6 shows the comparison between paired exercises (external rotation and extension) displaying the frequency of resistance band intensity with the most frequently used cuff weight resistance levels. With reference to the SLERW and PEXTW exercises, patients most often used yellow TB during ERB and EXTB (82, 74% respectively) when recorded to use the 1 lb. cuff weight, the yellow TB when recorded to use the 1.5 lb. cuff weight (41, 44% respectively), and the red (43%) or green (46%) TB when recorded to use the 2 lb. cuff weight.

Table 5.

Statistical Comparison of OMNI-RES Mean Scores for Shoulder ER and Ext Exercises

Exercise	N	SLERW	ERB	PEXTW	EXTB	t	p
ER Pair	64	4.41	5.13	—	—	-3.33	*0.001
Ext Pair	54	—	—	3.67	3.54	0.490	0.626

ER Pair: SLERW, ERB

Extension Pair: PEXTW, EXTB

N=Combined surgical groups of participants performing ER Pair, Extension Pair

Abbreviations: ER = External Rotation, Ext = Extension, SLERW = sidelying ER w/ cuff weight, ERB = external rotation w/ band PEXTW = prone extension w/ cuff weight, EXTB = extension w/ band

Table 6.

Shoulder ER and Ext pairing frequencies at varying resistance levels

Exercise:	SLERW			PEXTW
Resistance:	1 lb.	1.5 lb.	2 lb.	1 lb.	1.5 lb.	2 lb.
	N (%)	N (%)	N (%)	N (%)	N (%)	N (%)
	ERB			EXTB
Tan	TB 1 (6%)	—	—	—	—	—
Yellow TB	13(82%)	7 (41%)	3 (21%)	6 (74%)	7 (44%)	2 (18%)
Red TB	2 (12%)	6 (35%)	6 (43%)	1 (13%)	6 (37%)	4 (36%)
Green TB	—	4 (24%)	5 (36%)	1 (13%)	3 (19%)	5 (46%)

Abbreviations: TB = Thera-band®, N (%) = Number of participants (percent of total), lbs. = pounds, ER = External Rotation, Ext = Extension, SLERW = sidelying ER w/ cuff weight, ERB = external rotation w/ band PEXTW = prone extension w/ cuff weight, EXTB = extension w/ band

In analysis of the three surgical groups, the average OMNI-RES score average across all seven exercises was 5.2 for the labral repair group, 4.7 for RC repair group, and 4.2 for the SA group. Greater than 90% of participants were regularly performing SLERW, PEXTW, ERB, EXTB in the labral group, and SLERW, ERB, EXTB in the RC repair and SA groups (Table 7).

Table 7.

OMNI RES Averages by Surgical Intervention.

Surgical Group	Labral Repair		RTC Repair Shoulder		Arthroplasty
	N	Mean	N	Mean	N	Mean
Exercise:
1. SLERW	10	4.8 ± 1.9	20	5.0 ± 2.5	34	3.9 ± 2.0
2. EROB	8	6.8 ± 1.9	13	6.3 ± 2.7	23	5.0 ± 2.1
3. ERR B	7	4.4 ± 2.8	10	4.7 ± 1.8	17	4.4 ± 2.0
4. PEXTW	9	4.8 ± 1.6	16	3.3 ± 1.9	29	3.5 ± 2.3
5. PHABW	7	5.2 ± 2.3	8	5.0 ± 1.6	13	4.4 ± 1.9
6. ERB	10	6.2 ± 1.9	20	5.2 ± 2.8	32	4.8 ± 2.0
7. EXTB	10	4.4 ± 2.3	20	3.5 ± 2.1	31	3.2 ± 2.1
Average		5.2 ± 2.1		4.7 ± 2.2		4.2 ± 2.1

N=Participants in each surgical group performing exercise at all post-operative timepoints

Mean=Average OMNI RES±Standard Deviation

Abbreviations: SLERW = sidelying ER w/ cuff weight, EROB = external rotation oscillation w/ band, ERRB = external rotation and retraction w/ band, PEXTW = prone extension w/ cuff weight, PHABW = prone horizontal abduction w/ cuff weight, ERB = external rotation w/ band, EXTB = extension w/ band

DISCUSSION

When first introducing load to the shoulder of a postoperative patient, it is important to select low-level exercise with light resistance in attempt to protect healing structures.^7,10,23 Currently, a patient's subjective rating of exertion during or following exercise is not typically or perhaps seldomly utilized to inform or guide appropriate therapeutic exercise prescription for shoulder rehabilitation or in orthopedic practice in general, despite the high potential value for use as a reliable and valid predictor of physiologic response to exercise.^17,18,29 Given the general agreement across authors in support of a gradual rotator cuff exercise loading progression in the rehabilitation of the post-operative shoulder,^7,10,23 the results of this study can be used to inform clinicians of several exercises deemed to be low-to-moderate intensity per patient reported OMNI-RES scores. The current study found, when grouping all exercise and surgical groups, an average OMNI RES score of 4.5 + 2.1, with individual exercise averages ranging from, “somewhat easy” to “somewhat hard” (3.6-5.7). Of note, average perceived exertion across all exercise was found to be similar between labral repair (5.2 ± 2.1), RC repair (4.7 ± 2.2), and SA groups (4.2 ± 2.1). Therefore, clinicians can expect similar RPE scores following the completion of the selected exercise regardless of the specific surgery requiring rehabilitation.

In a clinical commentary on rehabilitation after arthroscopic rotator cuff repair, van der Meijden et al¹⁰ suggests that exercises showing low muscle activation, per EMG, should be selected in early stages, and strengthening exercises shown to have higher EMG values be introduced later in the rehabilitation process. If relatively low EMG activation is a goal for early rotator cuff loading exercise, the ability of a perceived exertion scale, such as OMNI-RES, to predict muscle activation would be clinically useful and desirable, especially when simultaneous EMG is not being utilized. Morishita et al³⁰ evaluated all current evidence on the relationship between RPE scales and load intensity during resistance training. During resistance exercise, increased ratings of exertion were found to accompany increased percentage of maximum voluntary contraction (%MVC),^20,31,32 number of repetitions performed,³³ EMG activity,^33,34 and isometric torque.³⁵ While there is no literature to support the use of RPE scales to guide the post-operative management of patients with shoulder pathology, the studies previously mentioned support the concept of a patient report of muscle work playing a role in clinical decision making among other factors such as physician protocol, surgical technique, tissue quality, post-operative timepoint, patient pain response, age, comorbidities, etc.

Shoulder external rotation exercises in standing using elastic resistance (ERB) and in sidelying with cuff weights (SLERW) are commonly employed in clinical practice to activate and primarily strengthen the shoulder external rotator muscles.^{22,25,26,34,36-39} When compared, free weight and TB resistance training have been shown to equivalently improve isometric strength in short-term resistance exercise programs.⁴⁰ With comparison of RPE of the external rotation exercise pair, the current study found ERB to be rated significantly higher than SLERW (OMNI-RES average: 5.13, 4.41, respectively p = 0.001). Of note, the clinical relevance of an OMNI-RES score comparison between two exercises found to be less than one point apart is currently unknown, but it is the opinion of the authors that these exercises can be considered highly similar in exertion levels. Andersen et al³⁴ also studied RPE (Borg CR-10) in this external rotation pairing with matching resistance for dumbbell and TB exercise (example: Red TB = 2.0-2.2 kg, dumbbell=2.0 kg), Green TB=2.6-3.0, dumbbell=3.0kg, etc.). Both this, and the current studies found low to moderate average RPE values for ERB and SLERW and small relative differences in RPE between such exercises (Average Borg CR-10 difference between ERB and SLERW: Red TB/2 kg: (0.5), Green TB/3 kg: (0.8).³⁴

OMNI-RES score averages across all exercises and surgical groups were found to be similar when comparing the 6- and 12-week post-operative time points with the AMD of a selected exercise ranging from (0.1-1.2). During the course of rehabilitation for patients in the current study regularly attending physical therapy at a private outpatient orthopedic clinic, resistance for a given exercise was increased when appropriate with consideration of post-operative tissue-healing stage, pain, RPE, etc. Therefore, higher TB/cuff weight resistance was used at the 12-week versus 6-week post-operative timepoint despite similar OMNI-RES scores. As previously stated, studies of healthy, non-surgical, non-rehabilitation research volunteers of varying age have reported a consistent increase in RPE with an increase in resistance for a given exercise.^{16-19,24,29,30,33-35,41} Improvements in strength and pain levels in the 6 week interval between data collection may explain this observed rise in exercise resistance without concomitant rise in OMNI-RES score in the current study.

The present study is the first to collect ratings of RPE for commonly prescribed rotator cuff and scapular stabilizer exercises selected for rehabilitation in a surgical cohort including labral repair, RC repair, and SA. While this study can inform clinicians of expected OMNI-RES scores following exercise for similar patients, future research on ideal exercise exertion levels for patients in early, middle, and late-stage rehabilitation programs would be of high value. The addition of patient RPE with resistive exercise as a factor used to guide post-operative shoulder rehabilitation may offer utility knowing the reported linear relationship between RPE, resistance level, % MVC, EMG activity, joint torque, and number of repetitions. If clinicians can use RPE ratings as a way to examine appropriateness of an exercise, this may provide additional objective monitoring alongside biofeedback and dynamometry. Future research on correlating joint loading, EMG levels and RPE during common shoulder strengthening exercises in a post-operative cohort could serve to confirm the concept of low RPE ratings during exercise with low risk of compromising a surgical repair and allow the formation of groups of exercise/exercise resistance to be employed at certain stages of rehabilitation.

Limitations of this clinically based study primarily include the application of findings limited to a post-operative shoulder patient group under the direction and care of one physical therapist. While certain surgery-specific cohort participant numbers were relatively small, when taken as a single post-operative cohort of 66 participants, stronger conclusions can be made from the descriptive information presented in this study.

CONCLUSION

Commonly prescribed resistance exercise in the rehabilitation following shoulder surgery show light-moderate ratings of perceived exertion using the OMNI-RES rating scale at both 6- and 12-week post-operative timepoints across three surgical procedures.