As women, we face a lot of barriers to being involved in sports, whether that be at an age-grouper or elite level. Trying to be an athlete of any ability and dealing with getting your period is not a fun time for anyone. All of us go through it, yet it is not something that is not often discussed with coaches, friends or training partners. We simply wake up one morning and our usually motivated self has disappeared overnight and be replaced by an exhausted, frustrated imposter.
Many women experience a range of symptoms during their menstrual cycle. This might include appetite changes, poor concentration and irritability; as well as physical symptoms like headaches, dizziness, abdominal cramps and fatigue. You can decide to try and fight it by digging yourself into a big training hole, or just flop onto the couch and call it a week. Many of us pass it off as an unavoidable nuisance and just manage life around it. Aside from the fun of having to change a tampon in a portaloo mid-ride, have you ever wondered how much your body’s cycle actually affect your performance in racing and training? And if so, is there anything you can do to mitigate the negative effects without sacrificing your health?
The majority of medical research projects involving women are deliberately done during the first 14 days of the cycle, when hormones are least active and are less likely to affect physiology. So, the general lack of information about how a woman’s cycle influences physical performance is not because it doesn’t occur, but because it is a difficult thing to study in the first place. Studies often use otherwise sedentary females, and measure things like maximal effort and explosive performance. They don’t seem to measure endurance performance- which is thought to be more influenced by the hormonal changes of the menstrual cycle.
The start of the cycle (Day 1) begins on the first day of your period. In those who have a “normal” cycle (called eumenorrhoeic) over the next 23-38 days the ovarian hormones, oestrogen and progesterone, fluctuate to support reproduction. The two main phases that make up the cycle are the follicular and luteal phase.
The Follicular Phase (Day 1 -14. Also called post- menstrual phase)
Hormones are low during the early part of this phase, but an oestrogen surge occurs towards the end in order to stimulate ovulation. It is defined as the more “oestrogen dominant” phase.
During this phase, core body temperature is lower due to oestrogen, so you might find you perform better during in a hot or humid session or race. It also promotes free fatty acid oxidation, which means more fat is available to your body to use for fuel. This may help by sparing some additional glucose for use later on in the event.
There is also some weak evidence to suggest that your mood is better at this time (we’ll take it!) as well as your self confidence and self perception.
The Luteal Phase (Day 14-28. Also called pre-menstrual phase)
Oestrogen drops after fertilisation and progesterone takes over, rising gradually in preparation for pregnancy.
Progesterone increases basal insulin levels and promotes insulin resistance. It causes changes to water and electrolyte balance resulting in fluid retention, increased body weight and increased circulating blood volume. This is stereotypically the phase that we don’t like because we feel heavy and crave carbohydrate foods.
Core body temperature is increased during this phase, which means the body’s cooling mechanisms don’t start to work until a higher inner temperature is reached. Slight increases in core temp can be game changers in triathlon, especially longer or hotter races when you want cooling measures to start as early as possible.
Some studies have shown an increase in resting and exertional heart rates, which is thought to be a response to the larger volume of fluid in the body. Higher respiratory rates have also been described, and is likely to be due to progesterones direct effects on the respiratory centres of the brain. Being aware of these changes for someone who trains to heart rate and perceived exertion can help you understand patterns that you might be seeing in the data- that some weeks your HR seems to be higher than others. Be aware that there are hundreds of variables that can influence your heart rate and exertion, but this is one that’s not commonly talked about.
One 2016 study using 100 female participants showed a significant decrease in VO2max in the pre-menstrual phase compared to the post-menstrual phase. This study used medical student volunteers and not elite athletes, so is likely more representative of those of us who are just starting out.
So what can you do about it?
Firstly, much of the information in this post relates to normally cycling women who are not using artificial hormones to control their cycle. Many sportswomen of all creeds and levels use some form of contraceptive agent to control the timing of their cycle. These are broadly broken up into systemic (whole body) hormones and localised (uterus only) measures.
Things like the pill, implanon and depo-provera injection are all systemic hormones that help prevent pregnancy. The pills can also be used to skip or time your menstrual cycle so that you’re racing at your most convenient and best hormonal time. The benefits are obviously that 1- you don’t get pregnant; and 2- you can prevent your hormones from taking you up and down every month. However, these hormones still get into your tissues and influence your body in a similar way to your natural ones. Some women are more sensitive to these and find that the systemic approach is not the best for them. (Sadly, there is no way to predict if it will happen to you or not!)
The other main option available is the Mirena IUD, which is a small T-shaped device that is inserted into the uterus and releases smaller amounts of hormone that acts locally. Only very tiny levels are able to get into the bloodstream, so it can be better for women not wanting to use systemic hormone therapy. This one gets my biggest thumbs up, and if you want to know more about it feel free to get in touch.
Ultimately, whether you are or aren’t using any of these it can be helpful to understand how your body functions throughout your cycle. Try keeping a journal of your cycle and training together to see if there are any patterns that emerge. Understanding your body and how it reacts to changes in the internal and external environment is a crucial step to improving your health and performance! I have definitely found that making some changes in my life has helped immensely. If you have any personal experiences to share, or any questions please comment or send me an email at firstname.lastname@example.org
Please note that none of the above is intended to replace medical advice that you would get from your GP!
Some of the sources I used for this post and some further reading.
(I have tried to include free text versions where possible!)