Demystifying the menstrual cycle –some biology revision

The menstrual cycle comprises two phases the follicular phase (egg production) from Day 1 to 14 followed by the luteal phase (womb preparation for pregnancy) from days 15-28. The start of the cycle, day 1 is when your period (bleeding) starts, as it ends around day 5-6 hormone production is ramped up triggering ovulation and the release of an egg on day 14. After ovulation your body prepares for pregnancy and the lining of the womb thickens ready to nurture the fertilised egg. If no egg implants in the womb hormone levels plummet triggering the whole cycle to start over. The image highlights how hormones fluctuate over the average 28-day cycle.

Menstrual Cycle

For the first 10 days of the cycle hormone levels are relatively low and women’s response to exercise is similar to that of a man. However, around the time of ovulation on day 14 oestrogen levels reach a peak (blue and grey bumps on graph) followed by a peak in progesterone about a week later (pink bump on graph). Female hormones are complex, but declining oestrogen is what brings about behavioural PMS symptoms such as mood swings, irritability, anxiety, anger, forgetfulness and decreased self-esteem.

How fluctuating hormones affect exercising

During the low hormone days of menstruation and the follicular phase exercise physiologists have shown that women tend to be stronger feel less pain and recover faster from exercise.

High hormone days in the luteal phase have been linked to reduced capacity to make and maintain muscle tissue, cool the body and maintain adequate hydration. Vigorous, prolonged exercise during this time such as marathon running in high temperatures can leave women at risk of heat stress and hyponatraemia (low salt levels).

Changing hormones around menstrual phase can have a negative impact on reaction time, neuromuscular coordination and manual dexterity, this may be most noticeable for women who play ball sports. Undulating hormones around this time can make also muscles and ligaments/joints lax and more vulnerable to injury with a potential increased risk of knee and back injuries.

Many of these unwanted performance related side-effects from these hormone fluctuations can be addressed through careful attention to your dietary and hydration needs.

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