Sex differences in wrist torque in patients with lateral epicondylitis-biomechanical risk factors for refractoriness.

Eccentric contractions of the wrist extensors worsen lateral epicondylitis, whose pathophysiology may involve sex differences in wrist torque. This study aimed to investigate sex differences in wrist torque in patients with lateral epicondylitis. The wrist extension and flexion torques of 22 patients with lateral epicondylitis (11 males; 11 females) were measured. Maximum muscle output over time was measured for 20 seconds, initial torque was defined as muscle strength, and the degree of eccentric contraction was quantified and defined as the eccentric contraction index. The affected/unaffected side ratio of the wrist extensor, extensor/flexor ratio of muscle strength, and affected/unaffected side difference of eccentric contraction index between sexes were statistically analyzed. Furthermore, correlations between wrist extensor torque, eccentric contraction index, and visual analog scale of pain during the examination were evaluated. Females were found to display lower affected/unaffected side ratios of the wrist extensor and wrist extension/flexion ratios for the affected side, compared to males; however, no differences were found in the wrist extension/flexion ratios for the unaffected side in both sexes. Additionally, females presented with larger differences between the affected and unaffected sides in the eccentric contraction index. Based on correlations between wrist torques, eccentric contraction index, and pain, females tended to suppress muscle output to prevent pain from eccentric contraction of wrist extensors more than males, which would induce an imbalance in muscle strength of the wrist extensors and flexors. This imbalance may result in chronic eccentric contraction of the wrist extensors with gripping, exacerbating lateral epicondylitis. This article is protected by copyright. All rights reserved.