Effectiveness of Different Methods of Resistance Exercises in Lateral Epicondylosis—A Systematic Review

Article Outline

• Abstract
• Purpose of the Study
• Methods of Review
  • Search Strategy
  • Selection
• Results
  • Results of the Study
    • Isotonic (Concentric/Eccentric) Exercises
  • Exercises Combined with Conventional Therapy in the Treatment Group
  • Eccentric Exercise Alone Compared with a Control Group
  • Eccentric Exercises in Both the Treatment and Control Group
    • Isometric Exercises
    • Isokinetic (Eccentric) Exercises
  • Outcome Measures Used across Studies
• Discussion
  • Dosage of the Exercise Programs
  • Duration of the Exercise Programs
  • Rationale for Choosing Exercise Programs
  • Design of the Exercise Programs
  • Adherence by Participants
  • Outcome Measures
• Limitations
• Research Gaps/Directions
• Conclusion
• Appendix A. Evaluation of Quality of an Intervention Study
• Supplementary Data
• References
• Copyright

Abstract 

Study Design

Systematic Review.

Introduction

Lateral epicondylosis (LE) is relatively common with an annual incidence in the general population of 1% to 3%. Systematic reviews have identified exercise is effective, but have not established specific exercise parameters.

Purpose

The purpose of this systematic review was to synthesize the quality and content of clinical research addressing type and dosage of resistance exercises in lateral epicondylosis.

Methods

Computerized bibliographic databases (1990–2010) were searched using relevant keywords; bibliographies of included papers were hand searched. Of 594 screened abstracts, 11 articles (12 studies) met inclusion criteria. Articles were randomly allocated to pairs of reviewers who independently verified data extraction and appraised the full text, using a structured critical appraisal tool with 24 items. Data extraction was limited by a lack of consistent reporting of elements of exercise dosage.

Results

The mean quality rating of the studies was 72%, with 2 papers exceeding 75% quality. Of the 12 studies, 9 addressed the effects of isotonic (eccentric/concentric) exercises, 2 studied the effect of isometric and one studied isokinetic exercises. The exercise programs ranged over a period of 4 to 52 weeks. Exercises were prescribed 1 to 6 times per day, with an average duration of 15 minutes per session, and average of 15 repetitions (range: 3 to 50), with 1 to 4 sets per session.

Conclusion

All the studies reported that resistance exercise resulted in substantial improvement in pain and grip strength; eccentric exercise was most studied. Strengthening using resistance exercises is effective in reducing pain and improving function for lateral epicondylosis but optimal dosing is not defined.

Level of Evidence

2a.

Lateral epicondylosis (LE), commonly referred to as tennis elbow, is one of the most common soft tissue lesions of the arm.¹, ², ³ The estimated annual incidence in the general population is 1–3%.⁴, ⁵, ⁶ It is characterized by pain at the lateral epicondyle, aggravated by resisted muscle contraction of the extensor carpi radialis brevis. A clinical diagnosis is often founded on the basis of history and confirmatory physical signs, that is, pain over the lateral epicondyle, reproduced by resisted wrist extension.⁷ The extensor carpi radialis brevis is involved in 64% of patients,⁸ although approximately 35% of patients also have involvement of the extensor digitorum communis.⁹ Individuals at high risk for this type of overuse injury are those in the occupations of construction, assembly, manufacturing, food processing, and forestry.⁷, ¹⁰ There are reported gender differences in risk¹¹ with repetitive, monotonous work causative for women and precision demanding work for men.¹²

Many studies have proved that conservative treatment is effective in the treatment of LE.⁹, ¹³, ¹⁴, ¹⁵, ¹⁶ Systematic reviews have also confirmed that conservative management is effective.¹⁷, ¹⁸ Conservative management is often multimodal and resistance exercise program is a frequent component.¹³, ¹⁴, ¹⁵, ¹⁶, ¹⁹, ²⁰, ²¹, ²², ²³, ²⁴, ²⁵ Exercise programs that concentrate on eccentric loading have consistently been reported as effective because of the possible effects of stretching, lengthening, and increased tensile strength in the tendons;²⁶ but no reviews have addressed dosage or recommended a specific type of resistance exercise.

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Purpose of the Study 

The purpose of this systematic review is to investigate the quality of evidence specific to resistance exercises in LE, to extract details about exercise modalities and dosage and to synthesize this information into parameters for optimal exercise program.

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Methods of Review 

Search Strategy 

A search of Medline, Scopus, Cinahl, and EMBASE, from January 1990 up to and including December 2010 was conducted. Hand searching of the reference list of systematic reviews of conservative management of LE, and the reference lists of full-text articles retrieved was performed. Search terms used for inclusion were elbow, tennis elbow, LE, lateral epicondylitis, epicondylalgia, conservative treatment, exercises, resistance exercises, strengthening exercises, isometric exercises, isokinetic exercises, eccentric exercises, and concentric exercises. Studies that compared different interventions were included, if at least one group included strengthening exercise alone or part of a multimodal treatment program. Studies that investigated surgery, orthoses (splints), shock wave therapy, electrical stimulation, steroid injections, or casts were excluded. Additionally, the search was limited to English only, adults (age 18+ years), and humans. Out of the 594 abstracts identified, 52 were included for full-text review and 11 met inclusion criteria after full-text review (Figure 1).

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• Figure 1 

  Flow chart of search strategy.

Selection 

Reviewers examined titles and abstracts of the studies identified by the search strategy to select trials that met the inclusion criteria. Studies were included for full-text review if they were classified as relevant by at least one of the reviewers. The retrieved articles were reexamined by two other independent evaluators to ensure that they met the inclusion criteria. Twelve articles were numbered using a random number list and this list was then used to allocate the articles to pairs of raters. The studies were evaluated for their study quality by two independent evaluators using the critical appraisal form developed by Dr. Joy C Macdermid (Appendix A).²⁷, ²⁸ The form consists of 24 questions with a maximum score of 48. Studies with quality ratings of more than 75% were considered high quality; those with rating of 51–75% were considered moderate; and less than 50% were considered low. Raters met and resolved discordant responses. Levels of evidence were assigned using the table of levels of evidence described by the Oxford Center for Evidence-Based Medicine.²⁹

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Results 

Results of the Study 

We extracted data from 11 articles (one article described a pilot study and a clinical study as separate studies, hence the total number of studies included was 12) and reviewed the effect of different types of resistance exercises in improving pain and function in LE. A total of 12 studies were included in the review. Of these, seven studies¹³, ¹⁴, ¹⁹, ²⁰, ²¹, ²², ²³ were randomized controlled trials (RCTs), four studies¹⁵, ¹⁶, ²⁴, ²⁵ were nonrandomized clinical trials, and one was a cohort study.²¹ Out of the 12 studies, two studies reported the effect of isometric exercise, one reported the effect of isokinetic eccentric exercise, seven reported on isotonic eccentric exercise, and two reported on the effect of both isotonic concentric and eccentric exercise (Table 1).

Table 1. Description of the Studied Patients and Interventions

Study	Patients	Intervention		Outcome Measures
	No. of Subjects (n) Gender (M/F) Age Duration of Symptoms	Study Group	Control Group
Tyler et al., 2010	n=21 10 M; 11 F Age: Rx group: 47±2yr Control group: 51±4yr Symptom duration: Rx group: 6±2mo Control group: 8±3mo	Isolated eccentric wrist extensor strengthening exercise with: •Wrist extensor stretching, •Ultrasound, •Cross-friction massage, •Heat, and •Ice	•Wrist extensor stretching, •Ultrasound, •Cross-friction massage, •Heat, •Ice •Isotonic wrist extensor strengthening	1.DASH (pain and disability) 2.Muscle strength 3.Tenderness ∗Administered pre- and posttreatment after 7.2±0.8wk (eccentric group) 7±0.6wk (control group).
Park et al., 2010	n=31 Treatment group: n=16 7 M; 9 F Age: 50.3yr (range: 34–63) Symptom duration: 6.4mo (range: 2–15) Control group: n=15 5 M; 10 F Age: 50.0yr (range: 41–58) Symptom duration: 6.2mo (range: 2–17)	Isometric strengthening exercises	Isometric exercises with medication for the first 4wk	1.VAS 2.Modified Nirschl/Pettrone score 3.Mayo elbow performance score (pain and function) 4.ROM 5.Stability ∗Administered pre- and posttreatment at 1, 3, 6, and 12mo after intervention.
Luginbühl et al., 2008	n=29 (30 tennis elbow) 13 M; 16 F Age: 33–72yr Symptom duration: 1–60mo	1.Isometric grip strength exercise using a tennis ball. 2.Isometric resisted wrist extension exercise.	1.Treatment only with a forearm support band. 2.Combined treatment with a forearm support band and strengthening program.	1.Modified Nirschl/Pettrone score (pain and function) 2.ROM 3.Grip strength ∗Administered pre- and posttreatment and at 6wk, 3mo, and 1yr and followed-up after a mean period of 19±2mo (14–22mo).
Nilsson et al., 2007	n=78 36 M; 42 F Age: Rx group: 32–74yr Control group: 36–67yr Symptom duration: N/A	Eccentric exercises with wrist support, night bandage, static fitness training, stretching.	Symptomatic treatment.	1.PRFEQ, 2.Grip strength 3.Sick leave ∗Administered pre- and posttreatment at 4 and 16wk of initial visit.
Croisier et al., 2007	n=92 Control group: 46, 18M, 28 F Eccentric group: 46, 18M, 28 F Age: Control group: 38±8yr Eccentric group: 40±8yr Symptom duration: 8±3mo Control group: 8±3mo Eccentric group: 8±4mo	Isokinetic eccentric training combined with ice, TENS, ultrasound, deep friction massage, and stretching.	Nonstrengthening rehabilitation including ice, analgesic TENS, ultrasound, deep friction massage, and stretching.	1.VAS 2.Improvement in isokinetic peak torque. 3.Disability questionnaire. 4.Ultra sonographic examination ∗Administered pre-, at 4, 7, and posttreatment (9wk) of initial visit.
Stasinopoulos et al., 2006	n=75 46 M, 29 F Cyriax group=25, 16M, 9 F Exercise group=25, 15M, 10 F Bioptron group=25, 15M, 10 F Age: Cyriax group=40.4yr Exercise group=40.4yr Bioptron group=40.1yr Symptom duration: 5mo	Eccentric exercises	Treatment with Cyriax physiotherapy and bioptron light	1.VAS (pain) 2.VAS (function) 3.Pain-free grip strength 4.Dropout rate ∗Administered pre- and posttreatment (4wk) and at 8, 16, and 28wk
Manias et al., 2006	n=40 13 M, 27 F Exercise program and ice: n=20; 7M, 13 F Exercise program: n=20; 6M, 14 F. Age: (a) exercise program and ice: mean (SD) age 43.14 (6.15) yr); (b) exercise program alone: mean (SD) age 42.57 (6.31) yr). The mean age of the patients was about 40yr. Symptom duration: Minimum duration was 4wk. Mean duration was 4mo.	Eccentric exercise with static stretching	Eccentric exercise with static stretching and ice	1.Pain (VAS) 2.Dropout rate ∗Administered pre- and posttreatment (4wk) and at 16wk of initial visit.
Martinez-Silvestrini et al., 2005	n=94 50 M; 44 F Age: 45.5±7.7yr Symptom duration: >3mo	1.Stretching+concentric exercises. 2.Stretching+eccentric exercises	Stretching of wrist extensors	1.Pain-free grip strength 2.PRFEQ, 3.DASH 4.Short Form-36, 5.VAS ∗Administered pre- and posttreatment at 2 and 6wk of initial visit.
Struijs et al., 2003	n=31 (28 completed study) Manipulation group: n=13 9 M, 4 F Age: 46.3yr Symptom duration: 14.2wk Exercise group: n=15 6M, 9 F Age: 47.5yr Symptom duration: 9.3wk	Ultrasound, friction, stretching, strengthening (isotonic) exercises	Manipulation of the wrist	1.Global measure of improvement on a six-point scale. 2.Pain assessed with a 11-point numerical scale. 3.Pain-free grip force. 4.Maximum grip force. ∗Administered pre- and posttreatment at 3 and 6wk after intervention.
Svernlöv et al., 2001 (pilot study)	n=38 (30 completed study) Treatment group: n=15 13 M, 2 F Age: 42.1yr Symptom duration: 10.7mo Control group: n=15 6M, 9 F Age: 43yr Symptom duration: 8.4mo	Eccentric exercises with forearm support and wrist bands	Contract relax stretching program with forearm support and wrist bands	1.Pain (VAS) 2.Grip strength ∗Administered pre- and posttreatment (12wk), 6 and 12mo after treatment.
Svernlöv et al., 2001 (clinical study)	n=129 57M, 72 F Age: 46yr Symptom duration: 19.4mo (the patients were divided into two groups depending on the duration of symptoms—group 1 with symptoms<1yr and group 2 with symptoms>1yr)	Eccentric exercises (symptom duration: <1yr)	Eccentric exercises (symptom duration: >1yr)	1.Pain (VAS) 2.Grip strength ∗Administered pre- and posttreatment (12wk). At a mean of 41mo (range: 12–90) after treatment the outcome was evaluated using the scoring system described by Verhaar et al. (1995) and a four-grade self-rated outcome questionnaire using the alternatives: completely recovered, improved, unchanged, worse.
Pienimaki et al., 1996	n=39 14M, 25 F Exercise group: n=20 Age: 43 (33–53) yr Gender: 8M, 12 F Symptom duration: <6mo: 8 >6mo: 12 Control group: n=19 Age: 41 (31–53) yr Gender: 6M, 13 F Symptom duration: <6mo: 11 >6mo: 8	Isotonic eccentric and concentric exercises + stretching + occupational exercises	Ultrasound	1.Pain (VAS) 2.Disability questionnaire 3.Isokinetic muscle performance 4.Changes in sick leave 5.Clinical manual tests. ∗Administered pre- and posttreatment (2–8wk of initial visit).

DASH=Disabilities of the Arm, Shoulder, and Hand questionnaire; VAS=Visual Analog Scale; ROM=Range of motion; PRFEQ=Patient-rated Forearm Evaluation Questionnaire.

The resistance exercises included isometric exercise,¹⁹, ²² isokinetic exercise,¹⁵ isotonic,¹⁴, ²³ concentric,¹³ and eccentric exercises.¹³, ¹⁶, ²⁰, ²¹, ²⁴, ²⁵ All the studies compared the effectiveness of resistance exercises with a conventional treatment modality, which commonly included one or more of the following: wrist extensor stretching, ultrasound, heat, ice, cross-friction massage, forearm support band, TENS, Cyriax physiotherapy, and bioptron light, manipulation of the wrist (Table 1). Due to the variations in interventions (composition, dosage, and timing) and outcome measures used, we were unable to pool the data for statistical analysis and a narrative synthesis was performed.

Ten studies were of moderate quality¹³, ¹⁴, ¹⁵, ¹⁶, ¹⁹, ²⁰, ²¹, ²², ²⁴ and two were of high quality²³, ²⁵ (Table 2). The quality scores of studies ranged from 58% to 92%. One study was scored 44 (92%),²⁵ one was scored 40 (83%),²³ nine studies between 32 and 36 (67–75%),¹³, ¹⁴, ¹⁵, ¹⁶, ¹⁹, ²⁰, ²¹, ²² and one was scored 28 (58%).²⁴

Table 2. Summary of Study Quality

Seven¹⁴, ¹⁵, ²⁰, ²¹, ²⁴, ²⁵ studies reported a positive effect of resistance exercises on LE when compared with conventional treatment, whereas four studies¹³, ¹⁶, ¹⁹, ²² showed positive effects of resistance exercises over time but not when compared with the alternative treatment group. One study²³ reported that manipulation of the wrist was more effective than conventional therapy consisting of ultrasound, friction massage, isotonic strengthening, and stretching.

The exercise protocol, study quality, and results are presented in Tables 2 and 3 and the Supplementary Table, respectively.

Table 3. Exercise Parameters in the Treatment Group

Study	Muscle Action and Exercise Program	Intensity/Duration of the Program	No. of Repetitions	No. of Sets Per Session	No. of Sessions Per Day	No. of Weeks
Tyler et al., 2010	Muscle action: Isolated eccentric wrist extensor strengthening exercise. Program: The isolated eccentric strengthening exercise was performed using a rubber bar, which was twisted using wrist flexion of the uninvolved limb and slowly allowed to untwist with eccentric wrist extension by the involved limb.	Intensity was increased by giving the patient a thicker rubber bar if the patient reported no longer experiencing discomfort during the exercise.	15 reps. Each eccentric wrist extensor contraction lasted approximately 4sec (i.e., slow release).	Three sets with 30sec rest between each set.	1	7.2±0.8wk
Park et al., 2010	Muscle action: Isometric exercises. Program: The strengthening exercise program was composed of four sets of 50 repetitions daily.	10sec per repetition	50 repetitions	4	1	52
Luginbühl et al., 2008	Exercise 1: Isometric grip strength exercise using a tennis ball	20sec per repetition	20	1	2	12
	Exercise 2: Isometric resisted wrist extension exercise	20sec per repetition	20	1	2	10
Nilsson et al., 2007	Muscle action: Eccentric exercises. Program: The home training program lasted 15min and consisted of eccentric training of the flexor and extensor muscles, static fitness training, and stretching to be performed three times daily over 4mo. All the patients were offered a wrist bandage to use as a wrist support in their work, but only when necessary and for the purpose of relieving the pressure on the muscles of the wrist. 1.Supported wrist extension (dumbbells used in the later stages of the program). 2.Supported wrist flexion 3.Wrist extensor stretch	Self guided with a dumbbell Duration: 15min	Three to 30 repetitions of each exercise	1	3	16
Croisier et al., 2007	Muscle action: Isokinetic eccentric training. Program: Administered to the involved side using a Cybex Norm (Henley Healthcare, Sugar Land, TX) dynamometer. During each session, wrist extensors and forearm supinators were successively exercised. For the forearm supinators, patients were seated in front of the dynamometer with the forearm in a neutral position supported on a horizontal plane. The axis of the dynamometer was aligned with the forearm and the elbow was maintained at 60°of flexion. Wrist extensors were trained with subjects seated, the forearm supported on a horizontal plane and the elbow maintained flexed at 60°. The center of the wrist joint was aligned with the rotational axis of the dynamometer and the forearm placed in a pronation position.	Sessions 1–10: 30% MAX Sessions 11–15: 60% MAX Sessions 16–30: 80% MAX	10	2	Three sessions per week	9
Stasinopoulos et al., 2006	Muscle action: Slow progressive eccentric exercises of wrist extensors. Program: Eccentric exercises of wrist extensors were performed with elbow on bed in full extension, forearm in pronation, wrist in extended position (as high as possible), and the hand hanging over the edge of the bed. From this position, patients flexed their wrist, slowly counting to 30, then returned to the starting position with the help of the other hand. Patients were told to continue with the exercise even if they experienced mild pain. However, they were told to stop the exercise if the pain became disabling.	The supervised exercise program treatment was individualized on the basis of the patient’s description of pain experienced during the procedure.	10 repetitions	Three sets with 1min rest between each set.	Three sessions per week	4
Manias et al., 2006	Muscle action: Eccentric exercise. Program: Eccentric exercises of the wrist extensors were performed with the elbow on the bed in full extension, the forearm in pronation, the wrist in an extended position (as high as possible), and the hand hanging over the edge of the bed. From this position, patients flexed their wrist slowly while counting to 30, then returned to the starting position with the help of the other hand.	Individualized to each patient.	10	Three sets	Five sessions per week	4
Martinez-Silvestrini et al., 2005	Stretching±concentric exercise: Muscle action: Concentric exercise. Program: Concentric exercise was performed with the forearm in pronation by moving slowly from full passive wrist flexion to full wrist extension. The wrist was returned passively to full flexion after tension on the band was released by the opposite hand, so the band was lax and resisted eccentric contraction did not occur during the return to wrist flexion.	The appropriate resistance band (light, medium, or heavy) was determined by a 10 repetition trial.	10	Three sets with 2–5min rest between sets.	1	6
	Stretching±eccentric exercise: Muscle action: eccentric exercise. Program: The eccentric exercise was performed by first putting the pronated wrist into full extension by lengthening the band with the opposite hand so that it was lax and, thus, resisted concentric contraction did not occur during wrist extension. Next, the band was slowly lowered from full wrist extension to full wrist flexion. For each repetition, the band was lengthened by the opposite hand to position the wrist in extension without resistance on the band.	The appropriate resistance band (light, medium, or heavy) was determined by a 10 repetition trial.	10	Three sets with 2–5min rest between sets	1	6
Struijs et al., 2003	Muscle action: Isotonic exercises. Program: The exercises started with slow fist-clenching, resisted wrist movements, and wrist rotations with a stick (step 1), followed by movements against a band (step 2) and two-way resisted wrist rotations and pressing hands against a wall (step 3).	Resistance provided by a band, which varied according to the patient.	10	Two to three sets for each exercise.	Twice daily	6
Svernlöv et al., 2001 (pilot study)	Muscle action: Eccentric exercises. Program: 1.Warm-up of the forearm extensor and flexor muscles with wrist movements without any load (2–3min). 2.Static stretch (15–30sec). Repeated 3–5 times. 3.Eccentric exercises of the forearm extensor muscles (10sec). Elbow in 90° of flexion. 4.Static stretch, as prior to exercise. To be performed once daily	Individualized to each patient.	Five repetitions	Three sets	Once daily.	12
Svernlöv et al., 2001 (clinical study)	Muscle action: Eccentric exercises. Program: 1.Warm-up of the forearm extensor and flexor muscles with wrist movements without any load (2–3min). 2.Static stretch (15–30sec). Repeated three to five times. 3.Eccentric exercises of the forearm extensor muscles (10sec). Elbow in 90° of flexion. 4.Static stretch, as prior to exercise. To be performed once daily	Individualized to each patient.	Five repetitions	Three sets	Once daily	12
Pienimaki et al., 1996	Muscle action: Isotonic exercises. Program: The exercises started with slow fist-clenching, resisted wrist movements, and wrist rotations with a stick (step 1), followed by movements against a band (step 2) and two-way resisted wrist rotations and pressing hands against a wall (step 3).	Resistance provided by a band, which varied according to the patient.	10	Two to three sets for each exercise.	Four to six times daily	6–8

Nine studies¹³, ¹⁴, ¹⁶, ²⁰, ²¹, ²³, ²⁴, ²⁵ ranging from level 1b to 2b using a total of 542 subjects examined the effect of isotonic eccentric exercises in the treatment of LE. The quality of studies evaluating isotonic exercises ranged from 58% to 92% (Table 2).

Exercises Combined with Conventional Therapy in the Treatment Group 

Four moderate quality studies (study quality ranging from 58% to 75% [Table 2])¹⁴, ²⁰, ²¹, ²⁴ found that using isotonic/eccentric exercise along with other conservative treatment procedures such as stretching, ultrasound, massage, heat, ice, occupational exercises, wrist supports, and/or bands could decrease pain and improve function significantly. One high-quality study²³ (83% study quality [Table 2]) showed that manipulation of the wrist was more effective than conventional therapy with resistance exercises in improving pain and grip force. The isotonic/eccentric exercise in these studies were performed for 3–30 repetitions, one to three sets a session, one to six sessions in a day for six to 16 weeks (Table 3).

All studies reported a statistically significant improvement in grip strength in the treatment group compared with controls (Tyler:²⁰ grip strength: treatment group 79% vs. 15% controls, pain: treatment group 81% vs. 22% controls, Svernlov:²¹ pain and grip strength: treatment group 71% vs. 39% controls). Pienimaki et al.¹⁴ showed a group that performed isotonic exercise had improved isokinetic wrist flexion torque (45%), while this declined by 4% in the ultrasound group; maximum isometric grip strength increased 12% in the exercise group and remained unchanged in the ultrasound group (Supplementary Table).

Martinez et al.¹³ found that eccentric exercise performed for 10 repetitions, three sets a session, once per day for six weeks with stretching showed a trend for improved pain and function in LE; but the effect was not statistically significant from that produced by a combination of concentric exercises with stretching or stretching alone (Supplementary Table). This study included 94 subjects and had a quality score of 32 out of 48 with a quality rating of 67% (Table 2).

Struijs et al.²³ found that manipulation of the wrist was effective in improving pain and grip force when compared with conventional treatment, which included resistance exercises performed for 10 repetitions, two to three sets a session, twice daily for six weeks. This study included 28 subjects and had a quality score of 40 out of 48 with a quality rating of 83% (Table 2).

Eccentric Exercise Alone Compared with a Control Group 

One high-quality (Table 2) level 1b study (quality rating of 92%, n=75)²⁵ studied the effects of eccentric exercises and compared it with the effects of Cyriax physiotherapy and bioptron light in the improvement of LE (Table 1). The exercises were performed for 10 repetitions per set, three sets a session and three sessions a week for four weeks (Table 3). This study showed that the supervised eccentric exercise program produced the largest effect in the reduction of pain (+0.6 Visual Analog Scale [VAS] units when compared with Cyriax physiotherapy and +1.0 VAS units when compared with bioptron light), in the improvement of function (+0.7 VAS units when compared with Cyriax physiotherapy and +1.1 VAS units when compared with bioptron light), and improvement of pain-free grip strength (+7.1 pain-free grip strength units when compared with Cyriax physiotherapy and +10.7 pain-free grip strength units when compared with bioptron light). Eccentric exercise was superior at the end of the treatment and at any of the follow-up time points (weeks 4, 8, 16, and 28). The authors concluded that it should be the first treatment option for therapists when managing LE (Supplementary Table).

Eccentric Exercises in Both the Treatment and Control Group 

Two moderate quality level 1b²¹ and 2b¹⁶ studies have used eccentric exercises in both the treatment and control groups to study its effect on LE as a means of evaluating covariates that influence the effects of exercise.

Svernlov and Adolfsson²¹ (quality rating of 69%, n=38) (Table 2) compared the effect of eccentric exercises in two groups of LE patients who differed in their symptom duration (<1 year duration vs. >1 year duration of LE). The eccentric program consisted of five repetitions done for three sets, once daily for 12 weeks (Table 3). The exercise program significantly reduced pain (VAS at rest decreased from 0.9 at baseline to 0.1 at three months; VAS during grip reduced from 2.9 to 0.6 [Supplementary Table]), regardless of duration of symptoms.

Manias and Stasinopoulos¹⁶ (quality rating of 75%, n=40; Table 2) studied the adjunctive effects of stretching alone versus ice and stretching when combined with eccentric exercise. The eccentric exercise program was performed for four weeks with five sessions a week and each session consisted of three sets of 10 repetitions (Table 3). Patients achieved a decline in VAS pain score of about seven units in both groups (Supplementary Table). There were no significant differences in the magnitude of reduction between the groups at the end of the treatment or at the three-month follow-up. Because the adjunctive treatment groups both improved equally over time and the eccentric exercise program was identical, the effect of eccentric exercises alone could not be established.

Two moderate quality studies with a quality rating of 69¹⁹ and 71²² (Table 2) reported the effect of isometric exercises on LE. Both studied investigative adjunctive treatment and included isometric exercises in both the treatment and control groups.

One level 2b study by Luginbühl et al.¹⁹ (n=30) examined the effect of isometric exercises only (group 2) versus forearm support band only (group 1) versus a combination of both (group 3). The exercises were performed for 20 repetitions per set, one set per session, twice daily at the patient’s self-guided resistance for 12 weeks (Table 3). Although isometric exercise was effective in improving pain and grip strength, no significant difference was detected between groups. The study reported a change in the mean modified Nirschl/Petrone score for the three groups from 3.7, 3.4, and 3.1 at baseline to 2.6, 1.7, and 1.8 after 12 weeks. Grip strength changed from 83%, 80%, and 81% of the contra-lateral side to 102%, 122%, and 111% (Supplementary Table). These changes were not statistically significant between the first visit and latest follow-up (one year).

The second study to report the effect of isometric exercises on LE was done by Park et al.²² (n=31), which compared the effect of immediate isometric exercises with that of delayed isometric exercise after four weeks of oral nonsteroidal anti-inflammatory drugs. The exercise program consisted of 50 repetitions, each held for 10 seconds done for four sets, once daily for 52 weeks (Table 3). Although isometric exercise was effective in improving pain, stability, function, and ROM, significant difference between groups was detected only at the first-month follow-up. Measures at three, six, and 12 months after the initial visit were not statistically significant (Supplementary Table). The study reported a change in VAS for pain from 53.1 at baseline to 29.7 at first-month follow-up and 7.8 at 12th-month follow-up compared with a score of 52.1, 49.4, and 7.0, respectively, in the delayed exercise group (Supplementary Table).

One level 2b study by Croisier et al.¹⁵ (n=92, moderate quality score [67%, 32/48] [Table 2]) compared the effect of isokinetic exercises combined with conventional therapy (ice, TENS, friction massage, and stretching) to the effect of conventional therapy alone. The exercises were performed for a total of 10 repetitions per set, two sets per session, and three sessions per week for a total of nine weeks using a Cybex Norm dynamometer with intensity progressing from 30% to 80% MAX (Table 3). After a treatment duration of nine weeks, isokinetic exercises showed a significant improvement in pain (based on VAS) in both the exercise (6.9–1.2) and control groups (6.7–4.3) (p<0.001; Supplementary Table). The isokinetic performances measured as peak torque was statistically better in the exercise group (p<0.05).

Outcome Measures Used across Studies 

The VAS was the most common outcome measure used in the studies. VAS was used to measure pain¹³, ¹⁵, ¹⁶, ²², ²⁵ and function²⁵ in 66% of studies. Other common measures used to measure pain and function were of Disabilities of the Arm, Shoulder, and Hand questionnaire (DASH, 16%), Modified Nirschl/Pettrone score (16%), Mayo elbow performance score (8%), Patient-rated Forearm Evaluation questionnaire (16%), Short Form-36 (8%), and the Global measure of improvement (8%). Range of motion was measured using goniometer and pain-free grip strength was measured using dynamometer. Of the high-quality studies, two studies used VAS;¹⁶, ²⁵ one each used DASH²⁰ and Global measure of improvement scale.²³

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Discussion 

This study investigated the quality of evidence specific to resistance exercises in LE and extracted details about exercise modalities and dosage with the purpose of synthesizing evidence to define an optimal exercise program. Limitations in the scope of evidence that specifically addressed exercise dosage and the variability in study interventions and outcomes prevented pooling of data. Thus, specific optimal dosage could not be determined. However, our narrative review indicates that resistance exercises can reduce pain, increase strength, and function in LE.

This review indicates that patients with LE who perform isotonic eccentric exercises,¹³, ¹⁴, ¹⁶, ²⁰, ²¹, ²⁴, ²⁵ concentric exercises,²¹ isometric exercises,¹⁹, ²² or isokinetic exercises¹⁵ show positive changes in pain, strength, and disability over time (Supplementary Table), but the evidence about whether strengthening adds to improvement that occurs in a multimodal treatment program without strengthening is variable across studies. Seven¹³, ¹⁵, ¹⁹, ²⁰, ²¹, ²⁴, ²⁵ of the 12 studies used resistance exercises as the only treatment variable between the experimental and control groups. Five¹⁵, ²⁰, ²¹, ²⁴, ²⁵ of these studies demonstrated significant differences between the treatment and control groups supporting the use of strengthening exercise as a tool to improve symptoms in LE. Lack of power calculations and smaller sample size¹⁴, ¹⁶, ¹⁹, ²⁰, ²¹, ²² were contributing factors in the studies that failed to show a difference as the sample size varied from 21 to 40 in these studies.

Two studies²¹, ²² reported improvement in LE after three to 12 months of treatment and found no significant differences between the groups treated by resistance exercises or other forms of treatment, suggesting that more information is needed on long-term effects. Although one study²³ reported that manipulation was more effective than resistance exercises, the study was conducted for a short duration of six weeks and with a small sample size (n=31). Also, the subjects were advised to perform the exercises at home and their adherence was not documented. The same protocol for strengthening exercises has resulted in significant improvements in eight weeks in the study by Pienimaki et al.¹⁴

We attempted to extract dosage information relevant to exercise. We found that dosage was often not clearly specified. There were substantial variations in the interventions and outcome measures used. For these reasons, we were unable to define the most effective dosage parameters y. A further concern was the limited volume and quality of the evidence. Only 11 articles (12 studies) met inclusion criteria and of these only two were considered high quality.²³, ²⁵ Despite these limitations, we were able to perform a narrative synthesis that summarized what is currently known about exercise in LE and make specific recommendations for future research.

Dosage of the Exercise Programs 

For, repeatability or implementation of research, it is essential that the details of how exercise is assigned, progressed, and evaluated should be documented in studies. However, dosage is poorly addressed with respect to exercise descriptions. We attempted to extract data on the type of exercise used, intensity, number of repetitions, number of sets per session, number of sessions per day, frequency per week, and number of weeks of the exercise program. Rarely was this information complete. No articles described how the initial resistance was determined for individuals. Because strengthening is related to the load in relation to muscle capability, the lack of a specific method of assigning load for individuals is a substantial limitation. Nor was any rationale provided on how the progression or regression of the resistance was made as the patients’ symptoms or strength changed.

Duration of the Exercise Programs 

Strengthening programs ranged from four to 52 weeks in duration; repetitions per set ranged from three to 50, with one to four sets per session performed one to six times daily (Table 3). This range includes dosages that might be representative of exercise dosages for strengthening, assuming that the load applied was substantial when compared with maximum muscle capability (higher load/percentage of maximum, lower repetitions). Conversely, exercise dosages that might be used for increasing local muscle endurance would be expected to have lower load and higher repetitions. Most studies did not state the goal of the exercise program in relation to strength versus endurance; or if there was a progression in emphasis over the course of the program. It is difficult to determine goals on the basis of dosage alone, particularly when the dosage is not stated in reference to a measured maximum force or torque. There may be theoretical rationale for focusing on resistance exercise because increasing the cross-sectional area of the tendon and hence its tensile strength should be best accomplished by high load.²⁶, ³⁰ Conversely, local muscle endurance may be important for return to function. This emphasizes the importance of describing how the initial load was assigned in exercise studies. Ideally, the goal whether it be strengthening, endurance, or addressing another aspect of physical functioning should also be stated.

Rationale for Choosing Exercise Programs 

A physiologic or evidence-based rationale for choosing the exercise protocol was not explained in any study, although some authors had subjective reasons for the use of their particular protocol. The common reasons cited by the authors for choosing a protocol were that the particular strengthening program was not investigated well previously,²² or eccentric exercise being a novel exercise,²⁰ which had been effective in treating other tendinopathies.³⁰, ³¹ This also led to the difficulty in pooling the data of the exercise protocols because it is possible that for different subgroups of LE or stages of rehabilitation the goals of exercise might vary. Further, no studies described any contraindications for the exercise program, which raises concerns about both implementation and the validity of study findings.

Design of the Exercise Programs 

Most of the studies failed to report certain key elements in study design, characteristics of the subjects, and intervention. The details on blinding techniques used, sampling procedures, biases due to treatment providers, and missing data analysis were inadequate, thus reducing the quality of the studies considerably and accuracy in their results. With an increased emphasis on standards for reporting clinical trials,³² authors need to pay more attention while reporting both general standards and the specific exercise interventions.

Adherence by Participants 

Adherence to the exercise protocol by the subjects was a major area of concern. Not all the studies reported how adherent the patients were in following the exercise program as per the protocol. Five studies reported adherence,¹³, ¹⁵, ¹⁹, ²², ²⁴ whereas seven did not.¹⁴, ¹⁶, ²⁰, ²¹, ²³, ²⁵ Attention to adherence issues is a critical component of understanding the efficacy of exercise prescription. A recent systematic review³³ suggests that there is strong evidence that specific subgroups are at greater risk of poor treatment adherence, including those with low levels of physical activity at baseline or in previous weeks, low in-treatment adherence with exercise, low self-efficacy, depression, anxiety, helplessness, poor social support/activity, greater perceived number of barriers to exercise, and increased pain levels during exercise. Because these would be mediators on the effectiveness of the exercise program, recording of potential mediators of response and adherence should be considered both in clinical practice and efficacy studies. A 2010 Cochrane review³⁴ of interventions to improve adherence provides weak support that interventions such as supervised or individualized exercise therapy and self-management techniques may enhance exercise adherence. Randomized trials with long-term follow-up that explicitly address adherence to exercise; and better measures of adherence are needed.

Outcome Measures 

The estimates of effectiveness of exercise interventions are determined by the outcome measures used. Our review documented considerable variation across the outcome measures used. To assess whether an exercise produce the desired effect, a measure of its direct impact should be incorporated. This might include wrist extension strength and pain-free grip strength because the goals of wrist extensor strengthening would be both to improve muscle strength and reduce pain during gripping. However, the ultimate goal of hand therapy is to restore function and allow people to participate in their usual roles. For this reason, indicators of these concepts should routinely be incorporated as outcome measures to indicate the importance of strengthening exercises. The quality of studies is enhanced and the potential for meta-analysis to compare subgroups is improved if a standard set of core outcome measures could be adopted. The Patient-Rated Tennis Elbow Evaluation includes subscales that address pain and function; and has shown to be most responsive in this patient population.³⁵, ³⁶, ³⁷ Standardization of a single participation measure may not be possible because roles are variable. At a basic level, time lost from work or sport might be documented. The Work Limitations Scale has previously been used in this patient population³⁸ to examine role limitations after surgical intervention; but has not been used with conservative therapies.

Limitations in the number of studies and in their design prevented specific conclusive results about optimal dosage. Eccentric exercise has been most studied (9 of 12), and overall these studies were supportive of the positive effect of exercise on pain, strength, and function. Although current evidence provides the most support for eccentric exercise, this does not constitute proof that it is more effective than other forms of exercise. It is merely the most studied. Dosage trials that examine different intensities of exercise, and comparative trials that address different types of exercise programs are needed.

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Limitations 

The primary limitation in this review arises from the lack of high-quality trials that compared different exercise types or dosage; and the lack of detailed descriptions of exercise parameters in many published studies.

Although our database search revealed an adequate number of studies evaluated at level 2b or above (seven studies were at level 1b and five were at level 2b), methodological limitations were considerable (Table 2). Many of the studies failed to provide adequate enrollment,¹³, ¹⁴, ¹⁵, ¹⁶, ¹⁹, ²⁰, ²¹, ²², ²³, ²⁴ adequate follow-up,¹³, ¹⁴, ¹⁵, ²⁰, ²², ²³ blinding procedures,¹³, ¹⁴, ¹⁶, ¹⁹, ²⁰, ²¹, ²², ²⁴, ²⁵ information on the assessors and evaluators,¹³, ¹⁴, ¹⁵, ¹⁶, ¹⁹, ²¹, ²², ²⁴ and did not use either sample or power calculations or sample size justification.¹⁴, ¹⁵, ¹⁶, ¹⁹, ²⁰, ²¹, ²², ²³, ²⁴ The use of standardized outcome measures was another area of particular deficit; many studies used grip strength¹³, ¹⁹, ²¹, ²⁴ as an outcome measure instead of measuring wrist extensor strength, which is a direct measure of the affected anatomical part or pain-free grip strength, which is more responsive. Only a few studies reported resumption of roles such as return to work or the number of days on sick leave as a measure of improvement.¹⁴, ²⁴ Recruitment strategies were also often not described,¹³, ¹⁹, ²⁰, ²⁴ making it difficult to generalize results; furthermore, the size and significance of effects was absent in one study.²¹

There was particular lack of research addressing isokinetic and isometric exercise (one study on isokinetic and two studies on isometric exercises). There are very few studies that address the acute and chronic stages of LE. A computerized search of the database yielded only one study, which reported the management of LE in acute stages.³⁹ All the articles reported the effect of strengthening exercises on chronic LE.¹³, ¹⁴, ¹⁵, ¹⁶, ¹⁹, ²⁰, ²¹, ²², ²³, ²⁴, ²⁵

Finally, because the treatment program in the study groups is multimodal and eight out of 12 studies¹³, ¹⁴, ¹⁵, ¹⁶, ²⁰, ²¹, ²³, ²⁴ report the combined effect of resistance exercises with conventional physiotherapy, it can be difficult to isolate the effect of resistance exercises.

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Research Gaps/Directions 

The following research recommendations arise from this review:

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Conclusion 

There is moderate research evidence to suggest the use of isotonic eccentric exercise as a treatment program for LE; and weak evidence for the use of isokinetic and isometric exercise. Theoretical rationale suggests that progressive loading within a strengthening program is indicated for increasing tensile strength; and local muscle endurance training may be included if needed for function. Six out of nine studies,¹³, ¹⁴, ¹⁶, ²⁰, ²¹, ²³, ²⁴, ²⁵ which reported on isotonic exercises have concluded that an exercise program in the range of six to 12 weeks with three sets of exercises consisting of 10–15 repetitions is effective in treating LE. Thus, a protocol of eccentric exercises performed for three sets of 10–15 repetitions daily for approximately six to 12 weeks has the best current supporting evidence. Further high-quality research studies that meet the criteria specified above and that report studies’ outcomes using CONSORT criteria are needed, if we are to have stronger and clearer recommendations about the optimal application of exercise in LE.

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Appendix A. Evaluation of Quality of an Intervention Study 

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Evaluation of Study Design

Evaluation Criteria	Score
Study question	2	1	0
1. Was the relevant background work cited to establish a foundation for the research question?
Study design
2. Was a comparison group used?
3. Was patient status at more than one time point considered?
4. Was data collection performed prospectively?
5. Were patients randomized to groups?
6. Were patients blinded to the extent possible?
7. Were treatment providers blinded to the extent possible?
8. Was an independent evaluator used to administer outcome measures?
Subjects
9. Did sampling procedures minimize sample/selection biases?
10. Were inclusion/exclusion criteria defined?
11. Was an appropriate enrollment obtained?
12. Was appropriate retention/follow-up obtained?
Intervention
13. Was the intervention applied according to established principles?
14. Were biases due to the treatment provider minimized (i.e., attention, training)?
15. Was the intervention compared with appropriate comparator?
Outcomes
16. Was an appropriate primary outcome defined?
17. Were appropriate secondary outcomes considered?
18. Was an appropriate follow-up period incorporated?
Analysis
19. Was an appropriate statistical test(s) performed to indicate differences related to the intervention?
20. Was it established that the study had significant power to identify treatment effects?
21. Was the size and significance of the effects reported?
22. Were missing data accounted for and considered in analyses?
23. Were clinical and practical significance considered in interpreting results?
Recommendations
24. Were the conclusions/clinical recommendations supported by the study objectives, analysis, and results?
Total Quality Score (sum of above)=
Level of evidence (Sackett) 1 □ 2 □ 3 □ 4 □ 5 □

^©Joy MacDermid 2003.

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Supplementary Data 

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