The effects of menstrual cycle phase on the development of peak torque under isokinetic conditions

BACKGROUND: There are alterations in strength in relation to menstrual cycle phase but little data attributing these responses to female sex hormone levels using a pseudo-menstrual cycle group as control. OBJECTIVE: Examining the effects of menstrual cycle phase on the development of peak torque across a range of isokinetic speeds. METHOD: 17 well trained females, 11 formed the non-oral contraceptive group (n-OC) (age 20.7 ± 1.4 yrs, mass 59.2 ± 6.9 kg, height 166.8 ± 7.1 cm) and 6 the oral contraceptive control group (OC) (age 20.3 ± 0.5 yrs, mass 60.5 ± 4.2 kg, height 164.8 ± 4.8 cm). Concentric strength of the knee flexors and extensors (60–240°/s) was assessed, corresponding to menstruation (MEN), mid-follicular (mFOL), mid-luteal (mLUT) and pre-menstrual (pMEN). RESULTS: For n-OC significant decreases in peak torque production of the extensors at 120°/s (P=0.0207) (MEN) and of the flexors at 60°/s (P=0.0116) (MEN) and 120°/s (P=0.0282) (MEN) were observed compared to pMEN. No significant differences were observed across any menstrual cycle phase and peak torque for the OC group (p> 0.05). Significant positive correlations were observed (mLUT) between peak torque and oestrogen at 60°/s (P=0.040) and 120°/s (P=0.031). CONCLUSIONS: There are significant fluctuations in peak torque of the knee extensors in response to phases of the menstrual cycle associated with variances in the female sex hormones. The findings have implications for the planning of strength training in female athletes.