No Differences in Lactate Threshold Across the Menstrual Cycle in Untrained Females.

In addition to maximal oxygen consumption (VO2max), the Lactate Threshold (LT) is the other major determinant of aerobic exercise performance. This study examined the effects of the menstrual cycle (MC) phase on the LT in untrained females. Eight females and 8 males completed a LT test on a cycle ergometer. The tests were performed across three MC phases: early follicular (EF; menses), ovulatory (O), and mid-luteal (ML). The male participants (control group) were randomly assigned visits at similar time intervals as a regular 28-day cycle. Blood lactate was obtained during the last minute of each 3-minute stage of the LT test. The LT was determined by visual method (LT_vis), and fixed blood lactate concentrations of 2.0 mmol/L (LT_2.0mmol) and 4.0 mmol/L (LT_4.0mmol). There were no statistically significant differences in power at LT for any of the determination methods across the MC for the female participants (p>0.05) or across the time intervals for the male participants (p>0.05). The male participants tended to have higher power at LT for all three methods LT_vis (41.91W), LT_2.0mmol (44.68W), and LT_4.0mmol (55.94W). These findings support that the MC does not seem to influence power at LT in untrained naturally menstruating females.