During the average menstrual cycle, levels of the sex hormones oestrogen and progesterone change throughout each phase. These hormonal fluctuations cause changes in body temperature, the storage and use of energy, and the ability of muscles to produce force.
It’s the fluctuations in oestrogen and progesterone which are thought to have an impact on sporting performance. Research shows both oestrogen and progesterone promote the uptake and storage of muscle glycogen. Both hormones also change the ability to use this stored form of carbohydrate for energy – both during exercise and at rest.
Not only is the pill a common contraceptive method it’s also used by many women to alleviate symptoms of dysmenorrhoea (painful cramps) and menorrhagia (abnormal, heavy, or prolonged bleeding). Many athletes also use the pill to regulate and manipulate their cycles to coincide with training and competition schedules.
Recent research suggests that performance levels while taking the pill remain the same. However, there’s potentially a slightly negative impact of suppressing the ovarian hormones while taking the pill on athletic performance compared with non-pill users. This suggests that the consistently elevated concentrations of progesterone and oestrogen, as seen with a mono-phasic pill may impact on energy availability and use.
In the end, the impact a woman’s period or contraceptive use has on her performance is highly subjective. For example, former British tennis player Heather Watson exited the first round of the Australian Open in 2015 due to what she called “girl things” (“dizziness, nausea, low energy levels and spells of feeling light-headed”) – highlighting how the menstrual cycle is still a taboo topic. By contrast, when Paula Radcliffe first broke the marathon world record in Chicago in 2002, she was actually suffering period cramps in the final parts of the race.