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

Abstract

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, that is, the amount of a loss over time, and the muscle endurance ratio, that is, the 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/s for males and −0.038 Nm/s for females (p = 0.036); The muscle endurance ratio was 99.1%/s for males and 98.8%/s 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.

Pathophysiology of sex difference in refractoriness in lateral epicondylitis: Biomechanical study of wrist torque

“…We did not directly evaluate the prognosis of the patients. Resistance to LE treatment is multifactorial, including biological, environmental, and psychological factors 5,11,29 . A lower affected/unaffected side ratio of the MS(S) of the wrist extensor or an extension/flexion ratio of the MS(S) is only one of the biological risk factors for refractoriness.…”

“…Muscles are prone to eccentric contraction when muscle performance declines, including low muscle strength, contraction velocity, and endurance. 11 In patients with LE, muscle contraction velocity of the extensor carpi radialis delays, 13 and the strength of the wrist extensor reduces relative to the strength of the flexor. 14,15 As wrist extensors and flexors co-contract in gripping, 16,17 this muscle strength imbalance of the wrist may result in repetitive eccentric contractions with each gripping motion.…”

“…Uncontrolled conditions worsen histological severity with vascular fibroblast proliferation, mucoid degeneration, calcification, and ectopic ossification at the enthesis 7,9,10 . Decreased muscle strength and endurance of the wrist extensors are considered to be risk factors for the development of LE, because it induces an eccentric contraction of the wrist extensors in gripping with forearm pronation 11 . Although LE is considered a self‐limiting disease, about 10% of patients do not respond to conservative treatment and sometimes require surgery for refractory LE 9 …”

“…As LE exacerbates with repetitive eccentric contractions of wrist extensors, 7,8 female patients with LE would be expected to be more exposed to eccentric contractions than males. Muscles are prone to eccentric contraction when muscle performance declines, including low muscle strength, contraction velocity, and endurance 11 . In patients with LE, muscle contraction velocity of the extensor carpi radialis delays, 13 and the strength of the wrist extensor reduces relative to the strength of the flexor 14,15 .…”

“…5,11,29 A lower affected/unaffected side ratio of the MS(S) of the wrist extensor or an extension/flexion ratio of the MS(S) is only one of the biological risk factors for refractoriness. A longitudinal study with multivariate analysis would identify the risks more quantitatively.…”