Cerebral oxygenation declines but does not impair peak oxygen uptake during incremental cycling in women using oral contraceptives
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To compare prefrontal cortex oxygenation in recreationally-active women using oral contraceptives (WomenOC; n = 8) to women with a natural menstrual cycle (WomenNC; n = 8) during incremental exercise to exhaustion.
Participants performed incremental cycling to exhaustion to determine lactate threshold 1 (LT1) and 2 (LT2) and peak oxygen uptake (VO2peak). Prefrontal cortex oxygenation was monitored via near-infrared spectroscopy through concentration changes in oxy-haemoglobin (Δ[HbO2]), deoxy-haemoglobin (Δ[HHb]), total-haemoglobin (Δ[tHb]) and tissue saturation index (TSI).
17β-oestradiol and progesterone were lower in WomenOC (35 ± 26; 318 ± 127 pmol·L−1, respectively) than WomenNC (261 ± 156; 858 ± 541 pmol·L−1, respectively). There were no differences in full blood examination results or serum nitric oxide (p > 0.05). However, WomenOC presented lower concentrations in ferric-reducing ability of plasma (− 8%; effect size; ES − 0.52 ± 0.61), bilirubin (− 32%; ES − 0.56 ± 0.62) and uric acid (− 17%; ES − 0.53 ± 0.61). Cardiopulmonary parameters were similar between groups during cycling, including VO2peak (p = 0.99). While there was a significant effect of time on all parameters measured by near-infrared spectroscopy during incremental cycling, there was no effect of OC at LT1, LT2 or exhaustion calculated as a change from baseline (TSI; p = 0.096, Δ[HbO2]; p = 0.143, Δ[HHb]; p = 0.085 and Δ[tHb]; p = 0.226). The change in TSI from LT1 to LT2 was significantly different between groups (WomenNC; mean difference + 2.06%, WomenOC; mean difference − 1.73%; p = 0.003).
Prefrontal tissue oxygenation declined at a lower relative exercise intensity in WomenOC as compared to WomenNC, however, this did not influence VO2peak. The results provide the first evidence for variance in the cerebral oxygenation response to exercise, which may be associated with female sex hormones.
KeywordsContraceptives Oral Female Aerobic exercise Near infrared spectroscopy Prefrontal cortex
Beat per minute
Ferric-reducing ability of plasma
Gram per litre
Kilogram per square meter
- L·min− 1
Litres per minute
Lactate threshold 1
Lactate threshold 2
- min·week− 1
Minutes per week
- mL·kg·min− 1
Millilitres per kilogram per minute
- mmol·L− 1
Millimoles per litre
Millimeter of mercury
Picomole per litre
- rev·min− 1
Revolutions per minute
Reactive oxygen species
Rate of perceived exertion
Tissue saturation index
Peak oxygen uptake
Women with a natural menstrual cycle
Women using combined, monophasic oral contraceptives
Change or difference
Micromole of iron
Micomole per litre
This study was funded by Sport Performance Innovation and Knowledge Excellence unit, Queensland Academy of Sport.
Conception or design of the work: KQ, CM. Acquisition, analysis or interpretation of data: KQ, CM, FB, AB. Drafting of the work or revising it critically for important intellectual content: KQ, CM, FB, AB. All authors approved the final version of the manuscript and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All persons designated as authors qualify for authorship, and all those who qualify for authorship are listed.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
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