Velocity of the muscle tendon unit is sex-dependent and not altered with acute static stretch

Contraction velocity of a muscle tendon unit (MTU) is dependent upon the interrelationship between fascicles shortening and the tendon lengthening. Altering the mechanical properties of these tissues through a perturbation such as static stretching slows force generation. Females, who have inherently greater compliance compared with males, have slower velocity of MTU components. The addition of a static stretch might further exacerbate this sex difference. The purpose of this study was to investigate the velocity of fascicle shortening and tendon lengthening in males and females during isometric maximal voluntary contraction (MVC) of the plantar flexors prior to and following an acute static stretch. The MTU was imaged with ultrasound and voluntary activation tested with twitch interpolation for the 5-s plantar flexion MVC, which proceeded and followed an acute stretch. For the 3-min stretch the ankle was passively rotated to maximal dorsi-flexion. The males were stronger (128.71 ± 7.88 Nm) than the femal...