HANDGRIP AND WRIST EXTENSOR STRENGTH RESPONSE TO COUNTERFORCE FOREARM BRACING IN A HEALTHY POPULATION. Joyce White*; Elizabeth Bird; Erica Douglas; Kathleen Edwards Physical Therapy, University of Massachusetts Lowell, Lowell, MA PURPOSE: The purpose of this study was to determine if counterforce bracing of the proximal forearm affects grip and wrist extensor strength in a healthy population. Three methods of applying the counterforce brace were examined: no brace, brace applied with light tension, and brace applied with heavy tension. BACKGROUNDS/SIGNIFICANCE: Lateral epicondylitis is a common condition attributed to overuse of wrist extensors during gripping and wrist activities. Counterforce bracing has been proposed to treat lateral epicondylitis by diminishing the force and overload of these structures, but prior research has been unclear as to the effects on healthy and patient populations. Few studies have standardized the tension used in applying counterforce braces when examining the effects of bracing. SUBJECTS: Forty-four subjects (25 women and 19 men, mean age 26 years) participated in this study. METHODS AND MATERIALS: Handgrip force and isometric wrist extensor force were measured with a hand dynamometer and hand-held dynamometer, respectively. A counterforce brace was applied 0.8 inch (2 cm) distal to the lateral epicondyle so that it was over the extensor carpi radialis longus and brevis. Six standardized grip force measurements were taken on the right hand: two without the brace, two with the brace applied with light tension (2.5 lbs), and two with the brace applied with heavy tension (5.0 lbs). Six wrist extension measurements were taken using a similar procedure. Distance from application of the hand-held dynamometer on the dorsum of hand to the radial styloid process was used to calculate wrist extension torque. Test order was randomized. Standardized positioning and instructions were used thoughout the measurement process. ANALYSES: Intratester reliability of grip and wrist extensor measurements were assessed by Pearson product-moment correlation coefficients and standard error of measurements (SEM). The two measurements recorded from each test were averaged for further analyses. One-way repeated measures ANOVA tests were used to determine differences in grip force and wrist extensor torque obtained from the three methods. A p-value of less than or equal to .05 was considered significant. RESULTS: Intratester reliability for measurement of grip strength (force) was high: r=.99 SEM=2.48 lbs for no brace, r=.95 SEM=5.35 lbs for light tension brace, and r=.98 SEM=3.32 lbs for heavy tension. Wrist extenson strength (torque) showed high intratester relibility as well: r=.95 SEM=.79 ft-lbs for no brace, r=.97 SEM=.65 ft-lbs for light tension brace, and r=.96 SEM=.75 ft-lbs for heavy tension brace. There was no significant difference in grip strength (F=.74, df=2, p=.48) or wrist extensor strength (F=1.02, df=2, p=.37) when comparing no brace, light tension brace, and heavy tension brace. Mean grip strength was 100.5 lbs for no brace (SD=24.7), 100.5 lbs for light tension brace (SD=23.9), and 99.5 lbs for heavy tension brace (SD=23.5). Mean wrist extensor torque was 10.6 ft-lbs for no brace (SD=3.6), 10.6 ft-lbs for light tension brace (SD=3.8), and 10.4 ft-lbs for heavy tension brace (SD=3.8). CONCLUSIONS: Counterforce forearm bracing applied with tensions of 2.5 lbs and 5.0 lbs had no affect on grip force or wrist extensor torque in a healthy population. The results of this study do not provide evidence that counterforce forearm bracing changes the ability of the wrist extensors to produce torque during gripping and wrist activities. Further research is needed which controls brace tension while examining the effects of counterforce forearm bracing in a symptomatic population. FUNDING SOURCE: No outside funding source. None of the authors have any potential for material gains as a result of the study. This material has not been or will be published or presented at another national or international meeting prior to June 8, 2005. KEYWORDS: brace, grip strength, isometric torque, lateral epicondylitis, physical therapy intervention Copyright 2009 by the American Physical Therapy Association. Requests for reprints should be directed to the corresponding author of the article. Educators, students, and other academic customers may receive permission to reprint copyrighted material from Physical Therapy (ISSN 1538-6724) by contacting the Copyright Clearance Center Inc, 222 Rosewood Dr, Danvers, MA 01923. Other types of customers who want permission to reprint should contact the APTA Editorial Office, Attn: Physical Therapy.