Altered anconeus muscle activation characteristics during isometric gripping in individuals with lateral elbow tendinopathy compared to age- and sex-matched control

Purpose: Individuals with Lateral Epicondyle Tendinopathy (LET) commonly experience gripping deficits, which are marked by pain and altered motor control of the forearm extensors and flexors. Although delayed activation of the anconeus muscle during rapid wrist extension has been observed in LET, its role during gripping is not well understood. This study aimed to investigate anconeus activation and its relation to forearm muscle activity during gripping in individuals with LET.

Methods: Eleven participants with LET and 11 healthy, age-, sex-, and limb-matched controls performed steady-state isometric gripping at 15% and 30% of their maximum voluntary contraction (MVC). Surface electromyography was recorded from anconeus and six forearm muscles. Standard clinical assessments for LET were conducted to evaluate the severity of the condition.

Results: Participants with LET exhibited increased relative activation of anconeus compared the forearm flexors, but not with the extensors, during both 15% and 30% MVC gripping. Additionally, the LET group demonstrated an increased coactivation ratio between anconeus and extensor carpi radialis brevis, as well as the flexor digitorum superficialis (FDS) during 15% MVC. At 30% MVC, this increased coactivation was observed between anconeus and all three flexors (FDS, flexor carpi radialis, flexor carpi ulnaris). Lower anconeus activation was associated with greater LET-related disability, while higher anconeus activation was associated with increased anconeus tenderness.

Conclusion: This study presents novel evidence of an adaptive motor pattern in LET, characterized by increased relative activation and coactivation of the anconeus muscle depending on grip force. Signs of maladaptive motor patterns emerge when grip force becomes painful. These findings enhance our understanding of anconeus dysfunction in LET and the gripping deficits that accompany it, offering new insights into potential management strategies for this condition.

Level of evidence: Basic Science Study; Kinesiology.