Efficacy of eccentric exercise program of wrist extensors on mechanical sensitivity and adaptive muscle activation strategy of forearm muscles in lateral epicondylalgia

The effects of eccentric exercise on mechanical sensitivity and forearm muscle activation in lateral epicondylalgia Sharon Tsang1, Wei Huang1, Shan Liu1, Huangjun You1, Tianqi Zhang1, Runyu Zhao1, Leanne Bisset2 1 Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hong Kong 2 Menzies Health Institute Queensland, Griffith University, Gold Coast, Australia BACKGROUND AND AIM : Altered mechanical sensitivity and forearm muscle activation are commonly displayed in people with lateral epicondylalgia (LE). Eccentric forearm extensor exercise has been advocated to promote pain and functional recovery. This study investigated changes in pressure pain threshold (PPT) and forearm muscle activation during gripping tasks and submaximal isometric wrist extension tasks, before and after a 5-week home-based eccentric forearm extensor program in participants with chronic LE. METHODS: Forearm muscle activation expressed in EMG amplitude (% MVC) and relative contribution between three extensor and three flexor forearm muscles during handgrip tasks (pain-free grip (PFG), 15% and 30% MVC) and isometric wrist extension tasks (15%, 30% MVC) were measured using bipolar EMG in 7 participants with an average of 3.2 years’ history of LE. Pain intensity (0-10), functional disability (Patient-Rated Tennis Elbow Evaluation) and PPT were also compared pre- to post-exercise. RESULTS: Pain and disability (p=0.038) but not PPT (p>0.05) significantly improved post-exercise. A significant increase in extensor carpi radialis brevis amplitude during PFG, decrease in flexor carpi radialis amplitude and increase in flexor carpi ulnaris amplitude and its relative contribution during 15%- and 30%-MVC grip were also found post-exercise. CONCLUSIONS: A 5-week home-based eccentric exercise program promoted functional recovery in LE, and was characterised by an adaptive activation strategy in selected forearm muscles. Further research should investigate the effects of an eccentric exercise program of a longer duration and as a component of a multi-modal intervention to better understand its efficacy and underpinning mechanisms in managing LE. KEYWORDS: lateral epicondylalgia, forearm muscle activation strategy, mechanical sensitivity