Effects of the menstrual and oral contraceptive cycle phases on microvascular reperfusion.

The objective was to examine whether the menstrual or monophasic oral contraceptive cycle phases affect microvascular responsiveness of the lower limb in healthy, active women. During the follicular or inactive-pill phase and the luteal or active-pill phase of the menstrual or oral contraceptive cycle, respectively, 15 non-oral contraceptive users (mean ± SD; 27 ± 6 years of age) and 15 monophasic oral contraceptive users (24 ± 4 years of age) underwent a lower-limb vascular occlusion test (5 min baseline, 5 min occlusion and 8 min post cuff release). Menstrual cycle phases were verified using an ovulation test. Vascular responsiveness was assessed by calculating the near-infrared spectroscopy-derived muscle oxygen saturation (StO2 ) reperfusion slope (slope 2 StO2 ) and the post occlusion StO2 area under the curve (StO2AUC ) of the tibialis anterior muscle. There were no differences in the reperfusion slope (as a percentage per second; follicular, 1.18 ± 0.48; luteal, 1.05 ± 0.48, inactive-pill, 0.95 ± 0.23; and active-pill, 0.87 ± 0.36; P = 0.09) and area under the curve (as a product of the percentage and seconds; follicular, 1067 ± 562; luteal, 918 ± 414, inactive-pill, 945 ± 702; and active-pill, 750 ± 519; P = 0.09) between the phases of the menstrual or oral contraceptive cycle, regardless of pill generation. The duration of oral contraceptive use was not associated with changes in slope 2 StO2 (r = 0.02, P = 0.94) or StO2AUC (r = -0.34, P = 0.22) between cycle phases. In conclusion, vascular responsiveness remained unchanged between the early follicular and mid-luteal phases of the menstrual cycle and the inactive-pill and active-pill phases of the oral contraceptive cycle.