Lateral epicondylalgia exhibits adaptive muscle activation strategies based on wrist posture and levels of grip force: a case-control study

OBJECTIVES: To investigate forearm muscle activity in individuals with lateral epicondylalgia (LE) when gripping at different wrist postures, and investigate the association between muscle activity and clinical characteristics of LE. METHODS: Eleven LE and 11 healthy participants performed isometric handgrips at 15% and 30% of maximum grip force (MVC). Gripping was performed in wrist extension, wrist flexion, and wrist neutral. Surface electromyography was collected from six forearm muscles. Standard clinical and tendon structural measures for LE were obtained. RESULTS: LE group had reduced magnitude of extensor carpi radialis brevis (ECRB) with increased contribution of extensor carpi ulnaris (ECU) during 15% MVC. However, during 30% MVC the LE group had reduced flexor carpi radialis and flexor digitorum superficialis activity, which was coupled with increased contribution from extensor digitorum communis (EDC) and ECU. Although ECRB and ECU activity differed in wrist flexion compared to other wrist postures for controls, different wrist posture had no effect on forearm muscle activation in LE. Pain and disability, and tendon thickness had significant associations with EDC and ECRB activity respectively in LE. CONCLUSION: Individuals with LE use different neuromuscular strategies when gripping with different wrist postures which appears to be dependent on the level of grip force.