The Application of an External Wrist Extension Force Reduces Electromyographic Activity of Wrist Extensor Muscles During Gripping

Abstract

Study Design: Experimental repeated-measures study. Objective: To investigate the effect of different extension forces applied to the palm of the hand on electromyographic (EMG) activity of the wrist extensor muscles during hand gripping. Background: Lateral epicondylitis is usually caused by repetitive wrist extension that leads to an overuse injury. The current theory is that the process of lateral epicondylitis begins with an overuse injury that leads to microtearing of the extensor carpi radialis brevis muscle and occasionally the extensor digitorum communis muscle. Use of an external wrist extension force might reduce muscle activity during gripping. Methods: Muscle activity was measured using surface EMG while subjects gripped at an intensity of 10%, 20%, and 30% of the maximum voluntary contraction force without, and with, an applied external wrist extension force of 1%, 2%, and 3% of maximum voluntary contraction. Results: Applying an extension force to the palm of the hand reduced EMG activity of the extensor muscles at the same strength generation during hand gripping. The muscles with the most significant reduction in EMG level, the extensor carpi radialis brevis and extensor digitorum communis, are those muscles that are most often involved with lateral epicondylitis. Conclusions: This study shows that an external extension force reduces EMG activity of the wrist extensor muscles during gripping in healthy volunteers. As the extension force increased, a greater reduction in muscle activity was noted.

Grip strength measurements at two different wrist extension positions in chronic lateral epicondylitis-comparison of involved vs. uninvolved side in athletes and non athletes: a case-control study

“…It is the most common source of elbow pain in the general population [2]. It is a soft tissue condition frequently associated with overuse injury, primarily occurring at the aponeurosis of the common extensor origin at the elbow.…”

“…The common complaints of the individual are pain during wrist extension which is localized to the common extensor origin and decreased grip strength, both of which may affect the activities if daily living [3]. Lateral epicondylitis or epicondylalgia is usually caused by repetitive wrist extension that leads to an overuse injury, followed by micro-tearing of Extensor Carpi Radialis Brevis (ECRB) and occasionally the Extensor Digitorum Communis (EDC) Muscle and Extensor Carpi Radialis Longus (ECRL) muscle [2,4,5]. Examination reveals pain with passive wrist flexion and active and resisted wrist extension.…”

“…The force overload implicated in lateral epicondylitis is attributed to the repetitive strong synergistic and fixator role played by the wrist extensors during gripping [2,3]. Gripping activates the flexor muscles thereby creating a flexion moment at the wrist joint and as a result the extensor muscles are co-activated, producing an extension moment that stabilizes the wrist joint.…”

“…Recent electromyographic studies have supported the concept that the wrist extensors play a key role in gripping and that ECRB, EDC, ECRL muscles are all activated during gripping [2]. It has been concluded that application of an external wrist extension force reduces EMG activity of the wrist extensors muscles during gripping in healthy volunteers [2].…”

“…It has been concluded that application of an external wrist extension force reduces EMG activity of the wrist extensors muscles during gripping in healthy volunteers [2]. …”