Sex Differences in the Morphological and Mechanical Properties of the Achilles Tendon

Abstract

Background: Patients with Achilles tendon (AT) injuries are often engaged in sedentary work because of decreasing tendon vascularisation. Furthermore, men are more likely to be exposed to AT tendinosis or ruptures. These conditions are related to the morphological and mechanical properties of AT, but the mechanism remains unclear. This study aimed to investigate the effects of sex on the morphological and mechanical properties of the AT in inactive individuals. Methods: In total, 30 inactive healthy participants (15 male participants and 15 female participants) were recruited. The AT morphological properties (cross-sectional area, thickness, and length) were captured by using an ultrasound device. The AT force–elongation characteristics were determined during isometric plantarflexion with the ultrasonic videos. The AT stiffness was determined at 50%–100% maximum voluntary contraction force. The AT strain, stress, and hysteresis were calculated. Results: Male participants had 15% longer AT length, 31% larger AT cross-sectional area and 21% thicker AT than female participants (p < 0.05). The plantarflexion torque, peak AT force, peak AT stress, and AT stiffness were significantly greater in male participants than in female participants (p < 0.05). However, no significant sex-specific differences were observed in peak AT strain and hysteresis (p > 0.05). Conclusions: In physically inactive adults, the morphological properties of AT were superior in men but were exposed to higher stress conditions. Moreover, no significant sex-specific differences were observed in peak AT strain and hysteresis, indicating that the AT of males did not store and return elastic energy more efficiently than that of females. Thus, the mechanical properties of the AT should be maintained and/or improved through physical exercise.

Challenging the Perceptions of Human Tendon Allografts: Influence of Donor Age, Sex, Height, and Tendon on Biomechanical Properties

“…Divergence in study conclusions may be associated with differences in donor cohorts and the tissues investigated, as well as the tendon dissection, preparation, and mechanical testing methods employed. Nevertheless, our findings are similar to human in vivo 20,23,25,42 and animal in vitro 32 studies citing sex differences in Achilles tendon properties, notably a larger CSA in males, 20,23,25,32,42 while demonstrating an absence of sex differences in a range of other tendons.…”

Tendon compliance and preload must be considered when determining the in vivo force–velocity relationship from the torque–angular velocity relation

“…The in vivo data of this study was obtained from male participants only. Previous investigations have demonstrated sex differences in mechanical properties of the triceps surae muscle–tendon unit, indicating that females tend to generate less muscle and tendon forces, exhibit shorter tendon lengths and smaller cross-sectional areas, and demonstrate more compliant tendons with a lower Youngs’s modulus compared with their male counterparts 52 – 56 . Therefore, the extent to which the in vivo F–v–r differs from the T–ω–r is likely to be influenced by sex.…”

Achilles Tendon, Patellar Tendon, and Femoral Cartilage Thickness in Control vs Asymptomatic Flatfoot Young Adults

“…Sample size was calculated by a statistical analysis program (SPSS Sample Power 3.0 Software; IBM Corporation, Armonk, NY), which showed that the minimum required sample size must be 28 participants for each group for the assumed alpha level (α) of 0.05 with the desired power (β) of 80% to detect a minimum difference of 0.3 mm for Achilles tendon when the mean tendon thickness in the control group is 4.4 mm with an SD of 0.4 mm. 39…”