An electromyography study of wrist extension orthoses and upper-extremity function

Objective. This study examined the effect of commonly used long and short s tyles of commercially produced wrist extension orthoses on the activity of the proximal muscles of the shoulder and elbow and on wrist flexor and exte nsor muscle activity. Method. While 17 women between 22 and 40 years of age (M = 26.6) performed a specified movement wearing each of the two styles of orthosis and without an orthosis, their motor unit recruitment of five proximal joint muscle gr oups, wrist extensors, and wrist flexors was measured by surface electromyo graphy. Results. Motor unit recruitment was significantly greater in bath orthosis conditions for four of five proximal muscles and for wrist flexors. There w ere no significant differences between the short and long orthosis conditio ns for proximal muscle groups. Conclusion. Wearing a wrist extension orthosis appears to place additional stress on the proximal joint musculature beyond that found without splint u se. The study has implications for the prescription of wrist extension orth oses, especially for patients whose proximal joints are already compromised .