The Effects Of The Menstrual Cycle On Isometric Knee Extension Strength

Females have often been neglected in health research because it has been unclear if their menstrual cycle affects their performance. There is data to show that some factors influence isometric knee strength in men though it has not been studied in females. The aim of this research is to determine if the menstrual cycle does play a significant role in females’ performance. PURPOSE: To peak torque and rapid torque development of the knee extensors are affected by the menstrual cycle. METHODS: Eight females (20.5 ± 0.5 year) who had regular menstrual cycle and were free of hormonal contraceptive visited the lab 7 times. The visits were in the following phases: menstruation (M): 24 and 96 hours after the first signs of menstruation, Follicular (F):24 and 72 hours after the end menstruation, Ovulation (O): within 24 hours of positive ovulation test, and Luteal (L): 5 and 10 days after ovulation. On each day the participants performed three maximal voluntary contraction of the knee extensors on an isometric dynamometer and 90 degrees flexion. Peak torque and rapid torque development at 50 and 200 ms where used for analyses. If there were two measurements for the phase the measurements were averaged, and a repeated measures ANOVA was run to determine differences between phases. RESULTS: For peak torque there was no significant difference between phases (F = 1.2, P = 0.3) with the values for each phase (mean ± SD), M: 136.4 ± 45.7, F: 145.5 ± 41.0, O: 144.5 ± 42.1, L: 153.9 ± 41.8 Nm. For rate of torque development at 50 ms was no significant difference between phases (F = 0.4, P = 0.8) with the values for each phase (mean ± SD), M: 1039.8 ± 47.5, F: 1003.5 ± 52.1, O: 1059.9 ± 53.9, L: 1178.2 ± 66.9 Nm/s. For rate of torque development at 200 ms was no significant difference between phases (F = 0.3, P = 0.8) with the values for each phase (mean ± SD), M: 468.4 ± 29.2, F: 462.4 ± 27.9, O: 498.5 ± 40.4, L: 493.4 ± 34.1 Nm/s. CONCLUSION: In conclusion, this data demonstrates that females’ isometric knee strength was not altered by the phases of their menstrual cycle. This study supports including women in more health research regarding females’ muscle strength.