Sex differences in wrist torque and endurance - Biomechanical factors associated with developing lateral epicondylitis of the humerus.

Since eccentric contractions contribute to the development of tendinopathy, sex differences in wrist torque and endurance may be involved in the pathophysiology of lateral epicondylitis and its refractoriness. Therefore, the present study investigated sex differences in wrist torque and endurance. The wrist extension and flexion torques of the 100 wrists of 25 males and 25 females were measured. The following parameters were assessed: muscle strength at the starting- and end point for the measurement, Δ muscle strength, i.e., amount of a loss over time, and the muscle endurance ratio, i.e., decrease rate over time. Each parameter in males and females was statistically analyzed. In wrist extension, muscle strength at the starting point was 6.1 Nm for males and 3.3 Nm for females (p <0.001); Δ Muscle strength was -0.052 Nm/sec for males and -0.038 Nm/sec for females (p=0.036); The muscle endurance ratio was 99.1 %/sec for males and 98.8 %/sec for females (p=0.015). In wrist flexion, muscle strength at the starting point and absolute value of Δ muscle strength were significantly larger in males than in females; No significant difference was observed in the muscle endurance ratio in wrist flexion between males and females. These results revealed sex differences in wrist torque and endurance. The muscle endurance ratio of the wrist extensors was lower in females than in males, which suggests that females need to exert more effort to maintain the wrist extension position under resistance. This may predispose the wrist extensor muscles in females to eccentric contractions. This article is protected by copyright. All rights reserved.