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

The influence of the different phases of the menstrual cycle on skeletal muscle contractile characteristics was studied in 19 regularly menstruating women. Muscle function was measured when (i) oestrogen and progesterone concentrations were low (menstruation), (ii) oestrogen was elevated and progesterone was low (late follicular phase), and (iii) oestrogen and progesterone were both elevated (luteal phase).Maximal isometric quadriceps strength, fatiguability and electrically stimulated 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 oestrogen, progesterone, follicle stimulating hormone and luteinising hormone. No significant changes were found in any of the muscle function parameters throughout the menstrual cycle (n = 15). The muscle function measurements showed no significant correlations with any of the female reproductive hormone concentrations. These results suggest that the fluctuations in female reproductive hormone concentrations throughout the menstrual cycle do not affect muscle contractile characteristics.