Forearm muscle activity in lateral epicondylalgia: A systematic review with quantitative analysis

BACKGROUND: Lateral epicondylalgia (LE) refers to pain at the lateral elbow and is associated with sensory and motor impairments that may impact on neuromuscular control and coordination. OBJECTIVE: This review aimed to systematically identify and analyse the literature related to the comparison of neuromuscular control of forearm muscles between individuals with and without LE. METHODS: A comprehensive search of electronic databases and reference lists using keywords relating to neuromuscular control and LE was undertaken. Studies that investigated electromyography (EMG) measures of forearm muscles in individuals with symptoms of LE were included if the study involved comparison with pain-free controls. The Epidemiological Appraisal Instrument was used to assess study quality. Data extracted from each study were used to calculate the standardised mean difference and 95 % confidence intervals to investigate differences between groups. RESULTS: The search revealed a total of 1920 studies, of which seven were included from 44 that underwent detailed review. Due to differences in outcome measures and tasks assessed, meta-analysis was not possible. The seven included studies used 60 different EMG outcomes, of which 16 (27 %) revealed significant differences between groups. Two were properties of motor unit potentials during wrist extension. Four were measures of increased time between recruitment of wrist extensor muscles and onset of grip force. Seven were measures of amplitude of EMG during tennis strokes. Three were measures of motor cortex organisation. CONCLUSION: Features of neuromuscular control differ between individuals with LE and pain-free controls. This implies potential central nervous system involvement and indicates that rehabilitation may be enhanced by consideration of neuromuscular control in addition to other treatments