The influence of menstrual cycle phase on skeletal muscle contractile characteristics in humans

1. The influence of the different phases of the menstrual cycle on skeletal muscle contractile characteristics was studied in 19 regularly menstruatin g women. Muscle function was measured when (i) oestrogen and progesterone c oncentrations were low (menstruation), (ii) oestrogen was elevated and prog esterone was low (late follicular phase), and (iii) oestrogen and progester one were both elevated (luteal phase). 2. Maximal isometric quadriceps strength, fatiguability and electrically st imulated contractile properties were measured. Isokinetic knee flexion and extension strength and fatiguability were also assessed as well as handgrip strength. Menstrual cycle phases were confirmed through measurement of oes trogen, progesterone, follicle stimulating hormone and luteinising hormone. 3. No significant changes were found in any of the muscle function paramete rs throughout thf menstrual cycle (n = 15). The muscle function measurement s showed no significant correlations with any of the female reproductive ho rmone concentrations. 4. These results suggest that the fluctuations in female reproductive hormo ne concentrations throughout the menstrual cycle do not affect muscle contr actile characteristics.