The Effects of Counterforce Bracing on Forearm and Wrist Muscle Function

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1 The Effects of Counterforce Bracing on Forearm and Wrist Muscle Function Mark A. Anderson, PhD, PT, ATC' Richard A. Rutt, PhD, PT, RN2 T he diagnosis of "tennis elbow" is frequently encountered by physicians and physical therapists in an outpatient ol-thopaedic setting. Nirschl and Pettrone (20) reported that they saw more than 1,200 cases of lateral tennis elbow from Over 870 patients with tennis elbow were treated at the Campbell Clinic from (3), and over 1,000 patients with tennis elbow were diagnosed at Duke University Medical Center from (4). It has also been reported that up to 45 percent of world-class tennis players and percent of average club tennis players have experienced symptoms of tennis elbow at some time (10, 16, 23). Because of its prevalence, it is important to have an understanding of "what is tennis elbow?". The term "tennis elbow" does not adequately describe either the condition or its cause. Various conditions about the elbow have been used to describe lateral elbow pain, including lateral humeral epicondylitis, common extensor tendinitis of the forearm, radioulnar synovitis, radiohumeral bursitis, and periostitis (4, 19, 27). The condition has also been related to a reflex localization of pain from radiculopathy at the cervical spine (I 1). However, the most prevalent thought regarding the etiology of tennis elbow seems to be an overuse injury of the extensor carpi radialis brevis, resulting in mi- Many factors may predispose development of tennis elbow. The purpose of this study was to evaluate the effects of two types of counterforce elbow braces on wrist and forearm muscle force. Subjects (N = 16) were randomly tested three times wearing no brace, brace I, or brace 2 on a KinComQ isokinetic dynamometer for wrist flexion/extension and forearm pronationlsupination for maximum peak concentric and eccentric muscle force at 60 and 24O0/sec. An analysis of variance for repeated measures was performed to determine any significant differences in muscle force for each of the three brace conditions or speed of testing conditions. There were no significant differences in concentric or eccentrk muscle force of any muscle group tested in any of the three brace conditions. Significant muscle force differences were found between the two speed conditions in some instances. There were no significant differences between muscle force and the speedlbrace interaction. It was concluded that neither type of counterforce elbow brace had any effect on ability of the wrist flexors/extensors or forearm pronators/supinators to generate muscle force in the normal population. Further research needs to be done to determine the effects of such braces in the involved extremity. Key Words: counterforce brace, tennis elbow, isokinetic testing Presented at the Sports Physical Therapy Section Team Concept Meeting, December 1991, New Orleans, LA. ' Associate professor and director of graduate studies, Department of Physical Therapy, University of Oklahoma Health Sciences Center, Oklahoma City, OK Assistant professor and research coordinator, College of Physical Therapy, Texas Woman's University-Dallas Campus, Dallas, TX This study was supported in part by a grant from the United States Tennis Association. croscopic rupture and subsequent tendinous nonrepair with immature collagenous scar tissue (20). The inflammation that results from this microscopic tearing of the tendon is consistent with the descrip tion of endogenous tendinitis described by Stanish et al (25), in which the tendon undergoes microruptures because it is not sufficiently strong to meet the expectation of the applied forces. It is not unreasonable to assume that these repetitive muscle forces are eccentric (1 4, 25), which have been shown to produce muscle damage in animals and humans (1, 6, 22). Nirschl has hypothe- sized that this is an important mechanism in the development of tennis elbow (1 7). While the name implies a predominance of this condition in tennis players, anyone involved in work or play that entails repeated pronation and supination with the elbow near full extension is at risk for developing tennis elbow (5). Thus, the condition is frequently seen in carpenters, surgeons, musicians, housewives, or others involved in this repetitive activity. Age may also be a predisposing factor in the development of tennis elbow. Priest et al (23) found that JOSPT Volume 15 Number 2 February 1992

2 the average age of male club tennis players experiencing pain from tennis elbow was 43 years, while women averaged 40 years of age. Ilfeld and Field (1 3) reported that tennis elbow occurred four times more frequently in individuals over the age of 40. Nirschl's random survey of 200 club players showed that half of those over age 30 had experienced symp toms related to tennis elbow (16). Conservative management of patients with tennis elbow has been shown to be of value in the majority of cases (3, 4). Conservative treatment such as rest; cryotherapy; antiinflammatory medication; therapeutic exercise for strength, endurance, and flexibility; equipment and/or technique modification; and the use of a counterforce elbow brace to reduce the overload forces on the affected muscle insertion have all been advocated (8, 12, 19, 2 1). Surgical intervention has been used only in the most severe cases that did not respond to conservative management. However, the results following surgery have been reported to be very satisfactory (3, 14, 15, 20). The counterforce brace has been widely used to both prevent and treat symptoms of tennis elbow. According tb Nirschl (18, 21). the counterforce brace provides a constraint to muscular contraction through two basic mechanisms: I) by providing dispersive pressure around the area of inflammation, the brace serves to broaden the area of applied stress to the common extensor tendon origin, thus, lessening the stress on the muscular attachment at the lateral epicondyle; and 2) by providing a restraint to full muscular expansion, the brace diminishes the potential force that the muscle can generate. Ilfeld and Field (1 3) compared the use of two specially designed elbow braces with traditional steroid therapy for the treatment of patients with tennis elbow. The two braces, an original and a revised model, were designed to limit elbow extension and forearm rotation and were worn by one group of subjects during work or recreational activities. Subjects treated with steroids received one to three injections of hydrocortisone and lidocaine (Xylocaine) hydrochloride. Results showed that bracing was effective 80 percent of the time, while other conservative protocols were ineffective. Investigators have also looked at the effect of counterforce bracing on forearm and wrist muscle function. There have been reports of decreased isokinetic torque production while wearing the counterforce It was expected that fhe lateral counterforce elbow braces would decrease the force production of the forearm and wrist muscles. brace (2 1). Conversely, increased isokinetic torque for wrist extension (26) as well as increased isometric wrist extension and grip strength on the affected side in subjects wearing a counterforce brace has also been reported (27). Groppel and Nirschl (9) found a decrease in extensor mass electromyographic (EMG) activity while hitting a serve or backhand shot in subjects wearing a counterforce elbow brace. Snyder- Mackler and Epler (24) also found a significant decrease in extensor mass EMG activity during isometric contraction of the wrist extensors in subjects wearing an Aircastm (Aircast, Inc., Summit, NJ) tennis elbow strap. However, no one has looked at the effects of counterforce braces on eccentric force production of the wrist and forearm muscles. The purpose of this study was to determine the effect of two types of lateral counterforce elbow braces on concentric and eccentric muscle force production of the forearm and wrist muscles. Because of a demonstrated decrease in the IEMG activity of the wrist extensors (24). it was expected that the lateral counterforce elbow braces would decrease the force production of the forearm and wrist muscles. METHODS Subjects Subjects (N = 17; 6 men, 11 women; mean age = f 8.9 yrs; mean height = in; mean weight = 139 f Ibs) were recruited from local tennis clubs. All subjects were club level tennis players with an NTRP (tennis ability rating) level of Subjects were normal, with no current or recent past history (within the past six months) of lateral epicondylitis or other elbow. forearm, or wrist pathology on the dominant extremity. By chance, all subjects were right hand dominant. Experimental Procedures Subjects were scheduled for two testing sessions. Testing was done on a KinComc* dynamometer. Each subject's dominant extremity was tested. Session one All subjects signed consent to participate forms as ap proved by the Institutional Review Board of the University of Oklahoma. Subjects were introduced to the training protocol and allowed to practice on the KinCom" until they felt comfortable with the testing apparatus and procedures. Subjects were then randomly assigned to begin testing with either no brace, brace 1 (ProC"' Tennis Elbow Brace, Pro Orthopedic Devices, Inc., Tucson, AZ) or brace 2 (Aircastm Tennis Volume 15 Number 2 February 1992 *JOSPT

Elbow Brace, Aircast, Inc., Summit, NJ). Subjects were then fitted with the appropriate brace (or no brace) and underwent initial testing.

contraction of the muscle group. The testing protocol consisted of a warm-up of 10 rep etitions, progressing from submaxima1 to maximal contractions.

Subjects were required to achieve three consistent force curves for each muscle group tested. Maximum peak muscle force was determined for each testing condition.

3 Elbow Brace, Aircast, Inc., Summit, NJ). Subjects were then fitted with the appropriate brace (or no brace) and underwent initial testing. Both counterforce braces were fitted a p proximately 1 in below the lateral humeral epicondyle with the brace pad placed directly over the common extensor muscle group as determined by an isometric contraction of the muscle group. The testing protocol consisted of a warm-up of 10 rep etitions, progressing from submaxima1 to maximal contractions. Subjects were tested on the KinComQ at two speeds, 60 and 240 /sec, concentrically and eccentrically, for wrist flexion and extension and forearm pronation and supination. Subjects were required to achieve three consistent force curves for each muscle group tested. Maximum peak muscle force was determined for each testing condition. Following session one, subjects were scheduled for their second testing session, with three days of rest between sessions, to allow for abatement of any muscle soreness resulting from the eccentric testing during session one. Session two Subjects were retested, using the same protocol, for the two conditions not previously tested (either no brace, brace 1, or brace 2), with a 30-min rest period between sessions. Statistical Analysis A 2 X 3 analysis of variance for repeated measures was performed to determine significant differences (P I 0.05) in muscle force for each of the three brace conditions (no brace, brace 1, brace 2), the two speeds of testing conditions (60 /sec, 240'1 sec), and the brace x speed interaction. RESULTS There were no significant differences ( p ) in concentric or ec- centric muscle force of any muscle group tested in any brace condition (Table 1). Significant muscle force differences (p ) were found between the two speed conditions in two instances: peak concentric wrist flexion and peak concentric wrist extension (Table 2). However, there were no significant differences in assessed muscle force of any other muscle group or types of contraction as a result of a change in joint move- ment velocity. Also, no significant differences (p ) were found in concentric or eccentric muscle force of any muscle group tested as a result of the brace X speed interaction (Table 3). DISCUSSION The results of this study differ from those reported by Nirschl (20), Stonecipher and Catlin (26). and Muscle Force DF ANOVA SS F Value P>F PEC PEE PFC PFE PSC PS E PPC PPE p < 0.05 TABLE 1. Effects of bracing on muscle force. Muscle Force DF ANOVA SS F Value P>F PEC ' PEE PFC * PFE PSC PS E PPC PPE ' p < 0.05 TABLE 2. Effects of speed of testing on muscle force. JOSPT Volume 15 Number 2 February 1992

While Nirschl reported decreased isokinetic torque production in subjects wearing a counterforce brace, no mention was made of the speed at which wrist extension was tested, or whether his subjects

4 Muscle Force DF ANOVA SS F Value PEC PEE PFC PFE PSC PSE PPC PPE p < 0.05 TABLE 3. Effects of brace x speed interaction on muscle force. Wadsworth et al (27). There are several possible explanations for these differences. While Nirschl reported decreased isokinetic torque production in subjects wearing a counterforce brace, no mention was made of the speed at which wrist extension was tested, or whether his subjects had a normal history or diagnosis of tennis elbow. Stonecipher tested concentric wrist extension strength at 30 and 1 20 /sec using a Cybexm isokinetic dynamometer. He used a pediatric blood pressure cuff around the forearm to simulate a counterforce brace and to control the amount of pressure with which the cuff was applied. Pressure from a counterforce brace would be greatest under the pad placed over the common extensor mass as opposed to equal around the forearm from a blood pressure cuff. While the same investigator placed the counterforce braces on all the subjects in this study, no measurement was taken in order to standardize pressure of brace application between subjects or between braces on a given subject. This might account for some of the differences in concentric wrist extension force production seen between studies. Since no EMG data were taken during this project, it is impossible to compare the results of this study with the findings of Snyder-Mackler and Epler (24) or Groppel and Nirschl (9). However, one would expect that if, indeed, IEMG activity is decreased in subjects wearing a There were no signircanf diflerences in concenfric or eccentric muscle force of any muscle group fesfed in any brace condition. counterforce brace, force production in those muscles should also decrease (2). However, in the study by Snyder-Mackler and Epler, IEMG activity for isometric wrist extension was assessed rather than during a concentric or eccentric muscle contraction, and the results may not be a p plicable to dynamic movement. Groppel and Nirschl used surface electrodes to assess IEMG activity of the wrist extensors during dynamic movement. Since the accuracy of using surface EMG electrodes during motion has been questioned, these results may not be valid. A more important note may be the finding of no significant difference in eccentric wrist extension force with or without a counterforce brace. If one believes that a primary cause of tennis elbow is a repetitive eccentric overload of the wrist extensors, using a counterforce brace as a preventative measure may have little value. However, because counterforce braces have been shown to decrease pain in subjects with tennis elbow (7, 27), the use of the counterforce brace may be of some benefit in the treatment of tennis elbow. CONCLUSION Neither type of counterforce elbow brace had any effect on the ability of the wrist flexors/extensors or forearm pronators/supinators to generate muscle force in club level tennis players without elbow pathology. Further study needs to be done as to how these braces may be effective in the treatment of tennis elbow. JOSPT REFERENCES Armstrong RB, Ogilvie RW, Schwane /A: Eccentric exercise-induced injury to rat skeletal muscle. j Appl Physiol 54:80-93, 1983 Basmajian jv, DeLuca Cj: Muscles Alive-Their Functions Revealed by Electromyography, 5th Ed, pp Baltimore: Williams & Wilkins, 1985 Boyd HB, McLeod AC: Tennis elbow. I Bone joint Surg 55A(6): , 1973 Coonrad RW, Hooper WR: Tennis elbow: Its course, natural history, conservative and surgical management. I Bone joint Surg SSA(6) , 1973 Cyriax /H: The pathology and treatment of tennis elbow. j Bone joint Surg l8(4): , Friden 1, Sjostrom M, Ekblom B: Myofibrillar damage following intense eccentric exercise in man. Int j Sports Med 4: , 1983 Froimson Al: Treatment of tennis elbow with forearm support band. / Volume 15 Number 2 February 1992 JOSPT

5 Bone loint Surg 53A: , Click 1, Nirschl RP, Bernhang AM, Priest /D, Ryan A/: Prevention and treatment of tennis elbow. Phys Sportsmed 5(2):32-47, Croppel 11, Nirschl RP: A mechanical and electromyographic analysis of the effects of various joint counterforce braces on the tennis player. Am / Sports Med 14: , Cruchow HW, Pelltier D: An epidemiologic study of tennis elbow: Incidence, recurrence, and effectiveness of prevention strategies. Am / Sports Med 7: , Cunn CC, Milbrandt WE: Tennis elbow and the cervical spine. Can Med Assoc / 1 14: , Halle /S, Franklin R/, Karalfa BL: Comparison of four treatment approaches for lateral epicondylitis of the elbow. / Orthop Sports Phys Ther 8(2):62-69, llfeld FE, Field SM: Treatment of tennis elbow. IAMA 195:67-70, Komi PV: Neuromuscular performance: Factors influencing force and speed production. Scand / Sports Sci 1:2, Leach RE, Miller /K: Lateral and medial epicondylitis of the elbow. Clin Sports Med 6(2): , Nirschl RP: Tennis elbow. Orthop Clin North Am 4(3):787, Nirschl RP: The etiology and treatment of tennis elbow. Am / Sports Med 2:308, Nirschl RP: Tennis elbow. Prim Care 4(2): , Nirschl RP: Soft-tissue injuries about the elbow. Clin Sports Med 5(4): , Nirschl RP, Pettrone FA: Tennis elbow: Surgical treatment of lateral epicondylitis. / Bone /oint Surg 61A(6): , Nirschl RP, Sobel 1: Conservative treatment of tennis elbow. Phys Sportsmed 9(6):43-54, Ogilvie RW, Armstrong RB, Baird KE, Bottoms CL: Lesions in rat soleus muscle following eccentrically biased exercise. Am / Anat 182: , Priest /D, Braden 1, Cerbierich /C: The elbow and tennis. Phys Sportsmed 8(4):80, Snyder-Mackler L, Epler M: Effect of standard and Aircast tennis elbow bands on integrated electromyography of forearm extensor musculature proximal to the bands. Am / Sports Med 17(2): , Stanish WD, Rubinovich RM, Curwin S: Eccentric exercise in chronic tendinitis. Clin Orthop 208:65-68, Stonecipher DR, Catlin PA: The effect of a forearm strap on wrist extensor strength. / Orthop Sports Phys Ther 6(3): , Wadsworth CT, Nielsen DH, Burns LT, Krull ID, Thompson CC: Effect of the counterforce arm band on wrist extension and grip strength and pain in subjects with tennis elbow. / Orthop Sports Phys Ther 1 l(5): , 1989 JOSPT Volume 15 Number 2 Februa~ 1992

Electromyographic and Cinematographic

Electromyographic and Cinematographic Analysis of Elbow Function in Tennis Players with Lateral Epicondylitis John D. Kelley, MD, Stephen J. Lombardo, MD, Marilyn Pink,* MS, PT, Jacquelin Perry, MD, and