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THE EFFECTS OF THE MENSTRUAL CYCLE ON LACTATE THRESHOLD AND PSYCHOLOGICAL MARKERS IN FEMALES

Abstract

INTRODUCTION: Estrogen and progesterone are key hormones regulating the menstrual cycle (MC) and are known to influence metabolism and psychological parameters during exercise in females. PURPOSE: This study aimed to examine menstrual cycle effects on lactate threshold (LT) and psychological markers in females. METHODS: 8 females and 8 males participated in the study. LT tests were performed on a cycle ergometer during three MC phases: early follicular (EF; menses, days 1-3), ovulatory (O, within 24-hours of a positive ovulation test), and mid-luteal (ML, 7-10 days following O). Ovulation was determined through urinary levels of LH with an over-the-counter ovulation test. For the control group (males), tests were randomly assigned at intervals matching a typical 28-day cycle. Blood lactate samples were taken during the final minute of each 3-minute stage of the LT test, and end-test ratings of perceived exertion (RPE) were recorded. The first stage was set at 1W/kg of body weight, and resistance was increased by 0.5W/kg thereafter. LT was determined using fixed blood lactate concentrations of 2.0 mmol/L and 4.0 mmol/L. Participants rated their mood using a modified Profile of Mood States questionnaire (POMS) and pain using a visual analog scale (VAS) at the beginning of each session. RESULTS: Power at LT did not significantly differ between groups or across MC phases (p > 0.05). End-test power was significantly higher for males than females (p = 0.024, EF: 232.13 ± 82.97W vs 158.50 ± 31.22W, O: 227.63 ± 89.19W vs 149.13 ± 12.93W, ML: 233.25 ± 84.44W vs 149.06 ± 24.51W). End-test RPE was not significantly different between groups or across phases, but a large effect size was observed during EF in females (p> 0.05, ηp2 = 0.188, EF: 8.50 ± 1.69 vs 9.00 ± 1.20). Notably, female fatigue levels were significantly higher (p=0.025) than those of males across all phases (EF: 3.38 ± 4.10 vs 1.25 ± 1.04, O: 3.13 ± 2.42 vs 1.00 ± 1.07, ML: 4.25 ± 4.10 vs 1.13 ± 0.64). Pain was significantly higher (p=0.031) in females during EF compared to males and other MC phases (EF: 15.79 ± 17.40 vs 0.92 ± 2.21, O: 1.59 ± 2.11 vs 0.26 ± 0.74, ML: 2.80 ± 4.52 vs 0.28 ± 0.51). CONCLUSIONS: The MC does not significantly affect power at LT in, naturally menstruating females. Additionally, increased pain an

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