Influence of volar and dorsal static orthoses in different wrist positions on muscle activation and grip strength in healthy subjects

Abstract

Introduction Orthoses are indicated for injuries of the wrist, although there is weak evidence for its influence on extensor muscle activation patterns. The purpose of this study was to compare two designs of volar and dorsal wrist orthoses in several positions, from flexion to extension, by surface electromyography wrist extensor muscle activation and grip strength in healthy subjects. Methods We analysed extensor carpi radialis brevis and longus, extensor carpi ulnaris and extensor digitorum comunis muscle activity by surface electromyography. The volunteers performed maximum and submaximum (50%) isometric grips, which were evaluated with a Jamar™ dynamometer using volar and dorsal orthoses with several positions of the wrist (0°, 15° and 30°), both in flexion and extension ( p < 0.05). Results Our results showed a significant decrease in extensor muscle activation at 15° and 30° of wrist extension in both volar and dorsal orthoses at 100% and 50% of maximum task. A decrease was also found at rest at 15° of wrist flexion volar orthoses. Decreased grip strength was found at 15° and 30° of wrist flexion in both volar and dorsal orthoses. Conclusions Based on the results of this sample, we would suggest, as orthotic prescriptions, 15° or 30° wrist extension orthoses as a supporting therapeutic modality for performance in new studies with lateral epicondylitis in association with low-intensity grip activity; or 15° of wrist flexion volar orthoses for rest, depending on the chronicity of the disease and individual assessment. Future studies with symptomatic patients are needed to confirm these findings.