Menstrual Cycle and Physical Activity
It will come as no surprise to most of us that our menstrual cycles have an impact on our physical performance. It is well understood that as females, we have reduced muscle strength and slower muscle repair and remodelling than males. This is thought to be associated with our monthly menstrual cycles. What this all means is that we may be potentially more prone to biomechanics issues and increased musculoskeletal injury risk, combined with slower recovery rates.
The effects of your cycle can have a big impact on your strength and endurance over the course of a month.
Male athletes are on a 24-hour cycle with little or no change in their day-to-day regulatory systems. Female athletes, on the other hand, are running on a 28-35 day cycle, on average, with hormones fluctuating throughout the month from one cycle to the next.
Understanding this cycle, and how it affects our performance, can be the key to success and help to prevent injuries.
Everyone will have their own experience of how their cycle impacts on their performance, I know from tracking my own cycles that the highest risk time for injury for me is the late luteal phase due to general clumsiness at this time! Combined with reduced force production, this leaves me more prone to strains and sprains.
The menstrual cycle has four different stages, which I will briefly explain below.
Menstruation
This phase lasts for an average of 5 days and refers to the part of our cycle when we are menstruating. A drop in progesterone results in menstruation occurring. During this period, we may feel fatigued and experience painful cramps. It is important to focus on iron-rich foods to replace what is lost, and also to ensure adequate hydration.
Our sex hormone levels are at their lowest during this phase of the cycle, and so fatigue is normal.
This has important implications for exercise participation, as recovery times may need to lengthened between sessions. It is important to continue to participate in lower intensity exercise, as this will help to keep fatigue and menstrual cramps at bay.
Listen to your body and lower the tempo of workouts or sleep/rest more if necessary.
Follicular Phase
Days 6-12. During this phase, the lining of the uterus thickens and the body prepares for ovulation. Follicle activity also changes to promote reproduction. Oestrogen is the primary hormone driving these physiological changes.
Oestrogen is positively associated with muscle strength and power, increasing our ability to exert force.
For this reason, we are at our strongest during the 2nd half of the follicular phase, when oestrogen is at its highest. Oestrogen levels peak at ovulation.
Increased muscle mobility may be observed in the late follicular phase as oestrogen levels are higher. This may lead to increased injury rate in female athletes around the time of ovulation. Overall the rates of injury between male and female athletes does not appear to be significant, however, the severity of the injuries sustained is significant, with female athletes often experiencing poorer outcomes following injuries and more severe strains and tears at certain times of their menstrual cycle. This is thought to be as a result of the elasticity effect of high oestrogen levels, resulting in greater loosening of tendons and muscles.
Ovulation
Always occurs 14 days before menses, and so its exact day depends on the average length of your cycle. At this point in the cycle, our oestrogen levels are at their highest and there is also a rise in luteinizing hormone, which causes an egg to be released from the matured follicle in the ovaries. The body is most prepared for reproduction. After this phase, the oestrogen levels begin to drop.
With oestrogen at its highest level, we may be more prone to injury at ovulation, as explained above. Oestrogen receptors in our joints may lead to increased laxity at joints, resulting in lower stability.
Luteal Phase
Day 14-28 during this phase, the endometrium prepares for pregnancy by increasing the endometrial tissue and blood supply. The main hormones responsible for this phase are progesterone and oestrogen. The levels of these hormones are maintained by the corpus luteum, which is formed at the site of ovulation in the ovary.
Progesterone is responsible for the thickening of the uterine wall and the reduction in discharge associated with this phase of the cycle as the fertile window has passed.
In the event that an egg is not implanted in the endometrium at the end of the cycle, the corpus luteum will not remain dominant and the levels of progesterone and oestrogen will decline rapidly.
During the luteal phase, our core body temperature is elevated slightly due to increased progesterone levels. This increased body temperature can alter sleep patters, particularly in the late luteal phase. This will potentially result in less restful sleep for athletes. The rise in temperature can also impact our sporting performance, hindering performance in endurance events.
During the luteal phase, it is possible that our bodies are less efficient at metabolizing carbohydrates as an energy source, this can cause deterioration in performance in high intensity exercise activities. It is important to consider the need for pre-exercise fuel to combat this limiting factor during the later phases of the menstrual cycle.
Our progesterone levels are rising in the 2nd half of our cycle, and are at their peak in the 2nd half of the luteal phase prior to the onset of the menstrual cycle. During the luteal phase we are producing less force and power as elevated progesterone levels have a negative impact on our ability to exert muscular force and power.
We can often feel slower and more sluggish during this phase due to changes in body mass caused by bloating and water retention. Some studies have found that we may have a tendency to overestimate the impact of these physiological changes, as exercise feels more difficult at this time. Nonetheless, it is worth considering adjustment of the effort accordingly where possible using RPE (rate of perceived exertion) charts to prevent fatigue.
Understanding the patterns of the menstrual cycle and working with it rather than against it can be really beneficial and avoid injuries. Women who are exercising regularly can benefit from tracking their monthly cycles. Understanding that we are likely better able for power and strength based exercises with increased endurance in the mid follicular phase, prior to ovulation, means that we can map this out and target this time as our time to make gains in strength and power.
Whereas, in the luteal phase and early follicular phase we are likely to be more fatigued with lower oestrogen levels, so these are good weeks to programme lower intensity workouts and recovery weeks into our programming.
For those of us who have irregular cycles, it can be more difficult to predict the cycle's impact on performance and injury risk. There is mounting evidence that incidence of tendon injuries and muscle sprains are also higher when we are overdue our monthly cycle, although the mechanisms of this aren't fully understood.
Knowledge is power and so recording data such as the start of each cycle, and symptom experience throughout the month helps us predict training outcomes and learn when to push and when we might need to consider taking it easier in our programming.
Working with our cycle in this way allows us to make meaningful progress towards our fitness goals throughout the cycle and may help to reduce the risk of injury.
Of course, sometimes we have no control over when match day or race day will occur, but regularly working with your cycle will increase your overall endurance and strength. Adjusting the way we approach these events such as focusing on improved rest and recovery and pre-fuelling with a good source of slow releasing carbohydrate 30 minutes before kick off will all help to ensure a successful event no matter where in the cycle it falls.
Bibliography
Balachandar V, et al. (2017)Effects of the menstrual cycle on lower-limb biomechanics, neuromuscular control, and anterior cruciate ligament injury risk: a systematic review. Muscles Ligaments Tendons J. 10;7(1):136-146.
doi: 10.11138/mltj/2017.7.1.136. PMID: 28717621; PMCID: PMC5505581.
Carmichael M.A et al. (2021) The Impact of Menstrual Cycle Phase on Athletes Performance: A Narrative Review International Journal of Environmental Research and Public Health 18(4), 1667;
https://doi.org/10.3390/ijerph18041667
Martin D et al. (2021) Injury Incidence Across the Menstrual Cycle in International Footballers Frontiers in Sports and Active Living
https://doi.org/10.3389/fspor.2021.616999
Thiyagarajan DK, Basit H, Jeanmonod R. (2021) Physiology, Menstrual Cycle.
