Effect of the biceps Brachii tendon on elbow flexor force steadiness in men and women

Tendons are connective tissue that transmit force to the skeleton. Therefore, mechanical and material properties of the tendon, such as stiffness, strain, stress and Young’s Modulus likely influence force production and control. Men are steadier than women in maintaining isometric elbow flexion force, but the cause of this sex-related difference in force steadiness (FS) has not been established. To-date most FS studies have centred on absolute force as well as motor unit activity, with limited attention given to the interaction between muscle and tendon. The purpose of this study was to determine whether the mechanical properties of tendon differ between men and women, and whether this contributes to men being steadier than women. Ten men (23 ± 4years) and 10 women (22 ± 3years) who were healthy and recreationally active participated in a single session to evaluate maximal force, steadiness and tendon properties. Submaximal forces of 2.5%, 5%, 10%, 20%, 40% and 60% maximum voluntary contraction (MVC) were executed and FS as well as tendon properties were measured during these efforts. Contractions were randomized within and between individuals for the submaximal isometric elbow flexion contractions. All measures were undertaken during the 5 second steady state contraction executed in a neutral wrist position. Results indicated that men were significantly stronger (p < 0.001), steadier (p < 0.001) and the BB tendon was stiffer (p = 0.03) in men than women. Tendon stiffness and CV of force were strongly correlated (r² = 0.60; r = 0.77; p < 0.001) for women but moderately correlated (r² = 0.21; r = 0.46; p < 0.001) for men. Therefore, our results suggest that having a more compliant BB tendon is likely a contributing factor of less stability in the elbow flexors of women compared to men.Graduate Studies, College of (Okanagan)Graduat