The effect of use of a wrist orthosis during functional activities on surface electromyography of the wrist extensors in normal subjects.

Wrist orthoses are advocated for patients with lateral epicondylitis on the assumption that use of the orthosis decreases muscle activity of the wrist extensors during activities. The purpose of this study was to compare the amount of electrical activity, root mean square (RMS) calculated from surface EMG recorded over the wrist extensors, during activities when applying four conditions of wrist orthoses: dorsal; volar; semicircular; and no orthosis. Thirteen normal subjects (mean age 27.7 years) performed three lifting and two gripping tasks, repeated on three consecutive days under four orthotic conditions. Measured were RMS and maximum voluntary grip strength. Repeated measures ANOVA's indicated a significant decrease of RMS using the semicircular design during lifting (p < .0005). Grip strength decreased significantly using all three orthotic designs, but RMS recorded during gripping did not. It was concluded that application of a wrist orthosis reduces electrical activity of the wrist extensors less than anticipated and only during lifting.