Neuromotor Characteristics of Lateral Epicondylalgia

Abstract

Neuromotor dysfunction such as delayed upper extremity reaction time and altered wrist posture during gripping, are considered part of the pathophysiology in lateral epicondylalgia (LE). This might manifest as changes in the forearm muscle activity patterns in LE. In addition to a systematic review (Study 1) of the current literatures of forearm muscle activity in LE, this thesis presents three case-control studies that provide new insights into: the timing of forearm muscle activity during wrist extension reaction time (RT) (Study 2), the magnitude of forearm muscle activity during isometric gripping with different wrist postures (Study 3), and forearm muscle synergies during ramp and steady-state phases of isometric gripping (Study 4) in individuals with LE. This thesis also presents the association of forearm muscle activity with the clinical, sensory and tendon structural changes associated with LE. The systematic review identified consistent evidence of increased electromechanical delay and altered cortical excitability associated with the forearm extensor muscles in LE. These findings suggest both peripheral and central contribution to altered motor control in LE. The second study, which used intramuscular electromyography (EMG), provided evidence that delayed RT in LE is due to prolonged extensor carpi radialis brevis (ECRB) and extensor digitorum communicis (EDC) motor time, with no between-group differences in premotor time. Wrist extension RT was associated only with ECRB and EDC premotor time but not with extensor carpi ulnaris (ECU) premotor in LE. Increased duration of LE symptoms was associated with shorter RT, as well as shorter ECRB and anconeus premotor time.