Having done this sports-ing sort of thing for a while now, I know a lot of things about the way my body works; I can pick my heart-rate within about 5 beats per minute, I can sense very rapidly when explosion is imminent, and I can pick—roughly—when I will be good to back up from sessions and when I will be useless on the couch.
One other thing I have noticed in all my worldly oldness, is how the menstrual cycle impacts on performance. It’s pretty noticeable, for me at least, and can definitely impact upon riding and racing.
But a basic rundown…
Day 1 is your period. This is the start of the follicular phase. It usually lasts 3-5 days but, like anything, there are outliers.
Around a week (5—7 days) after your period starts, estrogen levels rise and then around day 10-14 estrogen surges along with lutenizing hormone triggering ovulation. This is the most variable part of your cycle.
After ovulation progesterone levels rise, the ‘luteal’ phase. This is the high hormone phase and that which is the most fixed in time-span (beginning around the day 15-period). Hormones peak around 5 days prior to your period, often coinciding with all the other associated symptoms of PMS: tender breasts, skin changes, fluid retention/bloating and general malaise.
Most of the female readers here will know all this, however what is less common knowledge is how your hormonal factors impact your bike time.
The menstrual cycle affects our thermoregulation, metabolism, blood volume and mental focus. During your high-hormone phase (luteal, PMS), your body is more efficient at using fat as a form of fuel, conserving those glycogen stores. For ultra-endurance events this could have potential benefit (yet unproven). It can also mean that topping up the carbohydrate stores can be more important in order to perform well at higher intensities, and is certainly something to be aware of when racing at this time.
Also, at this time, core body temperature has a mild increase which can lead to reduced heat tolerance, a higher respiratory rate, and a potential for earlier onset of fatigue, especially in warmer climates (hello Australia!). Fluid needs are also increased.
Furthermore, many women report feeling less focussed, less motivated, more risk-averse and as having more difficulty with skill-based sports. I certainly know that when I have PMS I feel about as coordinated as a blue-footed booby-bird (hello my ride at the Golden Triangle Epic…jeepers corners much?). I struggle with fluid retention/bloating and more difficulty focussing on the task at hand. Hence, at this time being super-positive (in spite of what I may be feeling…) is really important if I am to finish a race strongly, as well as not being too self-flagellatory when I ride like a nana on a step-through frame in the singletrack.
Ideally, if I could race every race with my period or shortly after, I would, I would take the inconvenience for the mental clarity, feeling lean and fast that comes with being out of the high-hormone phase!
In conclusion, despite all mentioned above, Olympic gold has been won at every stage of the menstrual cycle and despite having explanations and physiological understanding of hormonal changes, jury is out on whether this effects race outcome at all.