Isometric knee-extension and knee-flexion torque production during early follicular and postovulatory phases in recreationally active women.

CONTEXT: Acute decreases in strength have been associated with risky biomechanical strategies that might predispose one to injury. Whether acute changes in thigh muscle torque occur across the menstrual cycle remains equivocal.
OBJECTIVE: We compared maximal voluntary isometric contraction (MVIC) torque of the knee flexors and extensors between the early follicular (EF) and either the early luteal (EL) or midluteal (ML) phases, which were confirmed by serum hormone concentrations. We expected that MVIC torques would increase from the EF to the EL phase after estradiol peaked and before increased exposure to progesterone.
DESIGN: Cohort study.
SETTING: Applied Neuromechanics Research Laboratory. PATIENTS OR OTHER PARTICIPANTS: Seventy-one recreationally active women (age range, 18-30 years). INTERVENTION(S): The MVICs were measured 1 day during menses and 1 day during the 8 days after ovulation. Participants were grouped by the hormone profile of their luteal test days as EL phase, ML phase, or anovulatory cycle. MAIN OUTCOME MEASURE(S): The MVIC torque of knee flexors and extensors (Nm/kg), estradiol (pg/mL), progesterone (ng/mL), and testosterone (ng/dL).
RESULTS: We tested 29 women during their EL phases, 32 during their ML phases, and 10 during anovulatory cycles. Although we observed relatively large individual changes in sex hormone concentrations and MVIC torques across the 2 test sessions, we observed no difference in MVIC torque between test phases (F(1,68)  =  1.17, P  =  .28) or among groups by test phase (F(2,68)  =  0.31, P  =  .74).
CONCLUSIONS: Thigh MVIC torque did not change from time of menses (when estradiol and progesterone were lowest) to time in the luteal phase after an unopposed estradiol rise or combined estradiol and progesterone rise. However, these findings were limited to MVIC torque production measured at 2 different times, and further research examining these relationships at multiple times and using other measures of neuromuscular function is needed.