Acute resistance exercise, not menstrual cycle phase, increases lipid oxidation rates following exercise in well-trained, eumenorrheic females.

Previous research supports the role of 17-β-estradiol (E2) and progesterone (P4) in altering lipid oxidation (LOx) rates during aerobic exercise, but it has yet to be determined if LOx is altered between menstrual cycle (MC) phases following strength-based resistance exercise (RE). This study examined post-exercise LOx rates in eumenorrheic females, following a bout of RE during the early-follicular, low hormone phase (LHP) and mid-luteal, high hormone phase (HHP). Twenty-two (age: 25.1±5.7 years; fat-free mass: 44.7±4.9 kg; relative strength: 1.2±0.2) well-trained females completed a repetition maximum (RM) test for the back squat, bench press, and deadlift. Participants then completed one resistance exercise session consisting of five sets of 3 repetitions at 80-85% 1RM for each exercise during the first 5 days of the participants’ MC (LHP) and once during the calculated mid-luteal phase (HHP). Metabolic testing occurred at baseline (BL) and again immediately post, 30-, 60-, and 90-min post-exercise. Despite expected hormonal differences in E2 (LHP = 1.53±0.58 pg/mL; HHP = 1.88±0.48 pg/mL) and P4 (LHP = 230.51±152.55 pg/mL; HHP = 545.22±295.72 pg/mL), there were no differences in LOx at any timepoint between MC phase (p>0.05). However, RE increased absolute LOx rates by ~49% compared to BL across the entire metabolic collection period (p<0.05), with the highest LOx rates recorded at 60-min post-exercise (0.077±0.016 g·min⁻¹, p<0.001). These findings suggest that RE acutely increases LOx rates above BL levels in well-trained, eumenorrheic females post-exercise, regardless of MC phase.