Exercise and “that time of the month”

Its something that many people don’t like to talk about. Many people see it as a bit of a taboo subject. But the reality is that half the population experience it…….a monthly menstrual cycle.

Many women wonder if their period has any effect on their sporting performance. Unfortunately, there is very little solid evidence that has been undertaken to determine this. The many studies that have taken place are usually very small, and the research processes aren’t the best, meaning the significance of the results is questionable.

stage - 4 of the Lotto Belisol Belgium Tour

While its difficult to provide a concrete answer, I will try to provide as much information on the subject as possible! Although I can’t give a definitive conclusion, what I have written is based upon the limited research which I have come across; as well as some of the thoughts from a few female athletes I have had a chat to about the subject.


Lets start with the basics……what actually happens in your body on a monthly basis? To put it simply, over the course of each menstrual cycle, the body undergoes changes in hormones, to develop and prepare the body to best allow you to become pregnant.

Here is a very crude diagram (apologies for the handwriting) from back in my uni days, which gives a brief summary of the hormone changes. Click here for more information on the different phases of the menstrual cycle.


As you can see, there is a big change in which hormones are present in the body across the monthly cycle! In theory, these changes in hormone levels may have some impact on sporting performance.


Many women will be familiar with PMS, while others will experience little to no problems over the course of each month. Due to the wide range of hormone changes that each individual experiences, and the body’s reaction to these changes, it is difficult to determine exactly what causes PMS; although it is often thought that these symptoms are worse in those individuals who produce less progesterone across their monthly cycle.


The symptoms of PMS are different for each individual; and the list of problems experienced can be quite extensive! Symptoms include insomnia, poor concentration, irritability, breast tenderness and appetite changes. Other symptoms such as joint and muscle pain, headaches, weight gain, low energy levels and an upset digestive system (bloating, constipation, stomach cramps) also affect many women.


There are 2 basic types of hormonal contraception available on the market……combined oestrogen and levonorgestrel (a synthetic form of progesterone), and levonorgestrel only tablets.

Combined oestrogen and levonorgestrel tablets provide a steady supply of the two hormones over a 21 day period, with a 7 day break where sugar tablets are taken. The constant addition of hormones to the body means that the usual process of the menstrual cycle, which ultimately prepares the body for pregnancy, is disrupted. During the 7 day sugar pill period, the reduction in hormones produces a bleed (known as a withdrawal bleed); so you can be assured of the regularity of your monthly cycle. With this type of hormonal contraception, the usual undulating levels of hormones in the body are over-ridden by the tablets…..so the hormone levels present during the 21 day “active” phase are fairly consistent.

Levonorgestrel only tablets are continuously taken over the course of the monthly cycle; providing a constant supply of one hormone to the body. These pills work in a slightly different manner than the combined pill. Monthly bleeds usually still occur; but many women experience “spot bleeding” every now and then, or even no bleeding at all!

In addition to tablets, levonorgestrel can also be given as an injection, where a small amount of drug is constantly supplied to the body over the course of 3 months…..the effects are the same as taking the tablet every day. Other devices, such as Implanon® (a rod which is inserted under the skin) and Mirena® (a device inserted into the cervix) supply continual small doses of progesterone over a 3 year period…..again, the effects should be the same as taking a daily tablet. These single ingredient types of contraception do not completely over-ride the normal hormone cycle; instead they work by providing a constant level of synthetic progesterone that is not normally present in the body……but the other hormones present in the normal menstrual cycle are still there.

Many women report that when they are taking some form of hormonal contraception, their periods are often lighter, and their PMS is more mild….although this is dependent on the individual. Hormonal contraception has also been known to cause heavier, prolonged bleeds, and worse PMS symptoms!


Some women decide that, when a big event or priority race is on the calendar, they want to use their hormonal contraception to “skip their period”…but is this okay? Well, yes! By skipping your period, you are able to avoid the “inconvenience” of your monthly bleed. In addition, by providing the body with a constant supply of hormones, you can theoretically reduce or avoid the symptoms of PMS for that period of time!

Skipping your period is easily done for women who are taking the combined oral contraceptive, by simply throwing away the sugar pills and continuously taking the active tablets. There is no evidence that any health problems are linked to skipping your period; and some women actually do this continuously for 12 months with no issues at all….but if you experience severe abdominal pain, chest pain, severe leg pain, vision changes or heavy bleeding, you should see a doctor immediately.



A small study of 8 women  measured ventilatory response in normally menstruating athletes, across 2 different phases of the menstrual cycle. It found that some of the ventilartory parameters being measured did vary between the 2 phases; but no performance changes were observed.

Another study of just 6 women observed the changes in muscle glycogen content in normally menstruating females. Again, this study was across 2 phases of the menstrual cycle. The results of the study suggested that exercise performance and muscle glycogen content are enhanced during one of the phases…..but this is only a suggestion. The conclusion is that exercise performance “may” change across the phases of the menstrual cycle.

A study with 13 women focused on cycling time trial performance across different stages of the natural menstrual cycle. The results of the study found that performance did improve (to a small degree) in one of the stages…..however, as the study only included women who showed significant hormone level changes across the menstrual cycle, the results are not really reflective of the general population.

From the hunting that I have done, the studies involving hormonal contraceptives and performance are very limited in their results. This is mainly due to the fact that so many different types of pills are available, containing varying doses and variants of hormones. Studies have been carried out……but small sample sizes, poor research design and research methodology means that the results between studies are not entirely consistent; and any solid conclusions cannot really be provided.


This is reflective of many of the research studies I have come across. The vast majority of research involves only very small numbers of individuals; and the results can vary from showing “no effect on performance” and “possible effects on performance”, to “some effects on performance” over the course of the menstrual cycle. In addition, many of the studies individually focus on a specific portion of effects on sports performance……oxygen uptake, glycogen storage etc. Any research focusing on the overall picture is lacking; but with the vast number of variables involved, research in this area is extremely difficult.


As you have probably already worked out, this is a fairly complicated subject! Everybody has slightly different hormone levels, and each individual is affected differently by their hormones. The addition of hormonal contraception adds another element to the equation; since the different types of contraception available work in slightly different manners…..and the varied intensity of PMS symptoms between individuals also confuses things!

In terms of hormones affecting performance, the evidence suggests that there may be some performance impact during different times of the monthly cycle for some individuals. But this evidence is very limited. Ultimately, due to the wide range of hormone changes, and the way each individual reacts to these changes, its impossible to give a “yes” or “no” answer. Some individuals may experience some changes in their performance, while others may experience no change at all.

As for PMS….the discomfort that many women experience on a monthly basis can be enough to affect sporting endeavours. Bloating, headaches, muscle tenderness, irritability and the other symptoms commonly associated with PMS can all have an impact on your performance. While this may not be a direct result of the hormone changes actually affecting your abilities, the mental aspect of not feeling your best can be more than enough to be a hindrance. How are you able to perform at your best when you aren’t feeling great??? But again, this will vary greatly between individual athletes!

For those on the combined hormonal contraceptive tablets, skipping your period may provide some benefits…purely from the fact that you might be able to avoid the hassle of a bleed. You may be able to reduce the discomfort from PMS symptoms, which could theoretically provide some performance benefits; or at the very least, minimise any reduction in performance! These benefits, of course, will vary between each individual!


Ultimately, there is not a definitive answer to the question! Most research studies are limited, and the results are lacking; but I would love to hear as many comments on the topic from female athletes as possible. Please….continue the discussion by leaving your comments below!

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