The Menstrual Cycle

Most exercise-nutrition research is based on male physiology.  This is because female physiology contains a few more variables than a males physiology.  For the sake of obtaining more reliable data, scientists reduce the amount of variables that they can control.  This results in studies primarily using male subjects.  This means that although the conclusions from these studies can apply to females, there’s a big piece of the jigsaw unaccounted for.

That piece is the menstrual cycle.  The monthly cycle that changes the physiology of half the worlds population.  Although the research is thin, and many of the findings contested, the menstrual cycle can affect VO2max, resistance training and a host over other performance related functions.

It is important to note that for each finding in a study, there is a disputing study.  This is indicative of an area that needs more research to solidify conclusions.   The findings however shouldn’t be disregarded and should be considered potentially relevant on an individual level.  The results from the current body of research might be useful for one individual but not apply to another.  So, if you’re reading this, perhaps it’s time to monitor your performance alongside your cycle and begin to draw correlations between the two.

Before I delve into the findings I’d like to give an extremely quick and simplistic overview of the relevant hormones in relation to performance in the menstrual cycle:  Oestrogen and progesterone.  This is not an in-depth analysis of the menstrual cycle.  It is a synopsis of research findings.

During the menstrual phase (approx. day 1-5), oestrogen and progesterone levels are low.  After menstruation ends oestrogen levels raise as menstrual cycle moves to the follicular phase and peaks just before ovulation on day 14.  After ovulation oestrogen levels drop and progesterone increases and peaks in the middle of the luteal phase (day 18 – 26).  Both oestrogen and progesterone levels drop towards day 28 and the cycle begins again. 

What the research is suggesting so far…

  • Oestrogen can have several effects on muscles during anaerobic exercises.  Oestrogen has demonstrated to increase glucose uptake in muscles during sprinting, whereas progesterone can inhibit this action.
  • Oestrogen can also act as protective in exercise induced muscle damage, resulting in a quickened return to baseline strength.  This is likely due to oestrogen’s capabilities of increasing satellite cell activation and proliferation.  Furthering this, oestrogen suppresses neutrophil and macrophage synthesis reducing the inflammatory response. 
  • Studies have demonstrated that in the follicular phase when oestrogen levels are high and progesterone levels are lower, participants had increased handgrip strength and experienced less fatigue. 
  • One study demonstrated that maximal oxygen consumption (VO2max) was lowered during the luteal phase.  However several studies reported no change across the cycle in VO2max levels.

There is some evidence to suggest that during the follicular phase (day 5 – 14), you’ll be at your strongest and have an increased ability to recover more efficiently.   If you are able to draw correlations between your cycle and your performance then perhaps this can guide your training.  Hitting your PB’s in weight and anaerobic activities during the follicular phase and a focus on repetitions and flexibility during the luteal phase.  

This article has not accounted for contraceptive interventions or the effects of the differing phases of the menopause on performance.

The body of research to this point does not provide enough support to alter training or competition strategies based on hormonal or menstrual status.  This may change as this area of study grows.  The information provided in this article may better inform you on why your performance varies across your cycle.

My advice:  Monitor, take notes, draw your own correlations and keep an eye out for new research in this area. 

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