The pharmacokinetic profile of oral contraceptives (OCs) results in an acute, transient increase in circulating synthetic reproductive hormones. The aim of this study was to examine the effects of acute OC ingestion on cognitive function, substrate metabolism and exercise performance. Sixteen combined OC (30 micrograms ethinyl oestradiol and 150mg Levonorgestrel) users ingested either their OC or placebo (PLA) in a randomised, double-blind, crossover manner. After 60 minutes, participants completed tests of verbal memory and verbal fluency, followed by sub-maximal treadmill exercise for 6 minutes at 60% lactate threshold (LT) and 90% LT where respiratory exchange ratio (RER), carbohydrate oxidation, fat oxidation, heart rate (HR), rating of perceived exertion (RPE), felt arousal and feeling scale were recorded. Participants then completed an incremental ramp test to exhaustion to assess time to exhaustion (TTE) and peak oxygen uptake (VO2peak), before ingesting the pill corresponding to the condition, they were not in. RER, arousal and feeling scale were all significantly lower in the OC condition compared to PLA (all P < 0.05) with no difference in HR, carbohydrate oxidation, fat oxidation, RPE, TTE or VO2peak (all P > 0.05). Verbal fluency score was significantly higher in the OC condition compared to PLA (P < 0.05), with no differences between conditions for any aspect of verbal memory (all P < 0.05). Combined OC ingestion acutely affects substrate metabolism, affective responses to exercise and verbal fluency. The timing of OC ingestion should be considered in relation to aspects of physiological function.

The authors have declared no competing interest.

NCT06560944

This project was supported by internal funding from the University of Lincoln.

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Ethical approval was received from the University of Lincoln Research Ethics Committee (718)

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