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Are hormones wreaking havoc with my running??

Updated: Jan 10, 2023

Historically, I haven’t spent much time thinking about how my menstrual cycle might impact my running.

That might seem like a strange thing to say, given that I’m a 36 year old female who has been having periods for 20 years and running for even longer. Why has this only become something I’m aware of in the last couple of years? It is probably in part due to the small amount of research and discussion in this area, and part due to my history.

The first part of my running life started in primary school when I started little athletics. My best results came when I was about 15. I got a few state medals and qualified for nationals. I first got my period around 16, which was also around about the time I started to struggle with running. Moving from little athletics to senior athletics was a challenge for me, when I found myself a bit out of my depth. I was good but not great, and my motivation started to dip. I’m not sure if my cycle had an impact of any of my races or training back then, because I wasn’t paying attention to it at all. Aside from potential low iron levels and tiredness, it never came up.

I stopped racing on the track when I finished high school. I still did a bit of running, but didn’t really start training again until I was in my mid 20s. I got more involved in road running, ran a sub 60 minute city2surf, a 41 minute 10km and did my first few half marathons in about 95 minutes. I was training 2-3 days a week, and while I liked running and wanted to improve, it wasn’t my top priority. I definitely remember having races that were hard or not as fast as I was hoping, but I generally put it down to not doing enough training. I was young and distracted by other things!

After a bit of a stint travelling overseas, I decided to stay put in Sydney for awhile, and start training again. This time, I took it a bit seriously. I ran my first marathon, built my training up to 5-7 days a week, and run faster than I ever imagined across all distances.

I went through the phase of improving a lot, due to putting in high volume for the first time in my life. I did a lot of quality training and did a lot of races I was really happy with. After about 4 or 5 years of more focused training, I noticed my enthusiasm starting to wane. I felt like I needed a bit of a break, and possibly a change to my training to keep improving. But overall, that period in my running life resulted in a lot of success.

During that time, from about 2012 to the end of 2017, I was on taking the pill. I was taking consistently at the same time each day, and rarely missed it. When I started taking it, I didn’t notice huge changes in my life or myself because I didn’t have particularly strong PMS symptoms before I started it. The only thing I really noticed that was missing was the emotional feeling I sometimes experienced the day before my period would arrive. But for the most part, I didn’t give it a second thought. And I definitely didn’t put any thought into what, if any, impact it might have on my running. I was taking it before I built my training up to a higher level, so I didn’t know what it was like to train hard while not taking it.

So what changed that has made me think about this now?

After I ran the Amsterdam marathon in 2017, I knew a break was on the horizon. I was feeling tired and like I had got almost the most I could out of myself at the time. I was planning to step back a bit from heavy training. At the start of 2018, I got married and our new top priority was having a baby. That obviously meant it was time for me to come off the pill.

My only initial concern was how long it would take to for my cycle to return to normal, because I wanted a baby ASAP. I was getting regular cycles again basically straight away, but I didn’t fall pregnant.

As each month ticked over and I didn’t get a positive, I started to want to race again. At first it was the Sydney 10, then the Gold Coast half marathon. I told myself I could enter and always drop out if I got pregnant. I wasn’t doing much speed work but I was doing quite a bit of running, and I had a good race at the Sydney 10.

Things got a lot tougher from there. I decided if I was going to run Gold Coast, I needed to do some faster running so I started doing some HM race pace sessions. July started with a tough run in the Gold Coast half, followed by my best run of the year, which was then followed by the toughest run I’ve had in a few years. Initially, I put the tough runs down to inconsistent focus between running and potential pregnancy. I decided to take a break from road races and entered a few trails runs.

It did occur to me though, that one big difference between 2017 and 2018 was that I had stopped taking the pill and was having a normal menstrual cycle again.

I started to do a bit of research into the impact of the menstrual cycle on running. I read that generally women tend to run better in the first half of their cycle than the second. I knew my “hardest run of the last few years” had occurred in the second half of my cycle, so I thought there might be something to it. It was enough to make me think that I might need to go back on the pill if I decided to enter another marathon. I was toying with the idea of running the Paris marathon in April 2019, but I didn’t want to do all the training and then have the race fall in the second half of my cycle.

Not long later though, I found out I was pregnant and thoughts of running and periods slipped well out of my mind. For the two years that followed, I thoroughly enjoyed not thinking about it due to pregnancy and breastfeeding.

While 2020 ended up being a mess for other reasons, I did manage to get a few races in. When my period was going to return was at the back of my mind, especially as it got closer to finally getting to run a marathon. I listened to a podcast and read a few articles on the topic, but without finding any definitive answers about what to do about it, I mostly thought of it as a problem for later.

The general consensus I’ve read is that the first half of your cycle, you are likely to have more energy and can tolerate harder training. The second half is where you might struggle and might be better doing less intensity. I’ve read the comparison between the cycle and seasons – comparing spring and summer to the portion of your cycle from when you get your period to ovulation, then autumn and winter being the portion after ovulation when might just want to hibernate. I’ve read the science behind it, hormone levels are lower in the first half of the cycle, and then rise in the second half to support a potential pregnancy, which is when you are more likely to feel heavy and tired.

What I didn’t read is what I’m supposed to do when a race falls in the second half of my cycle!

In December last year, the later problem became a now problem. My cycle returned, and with it the inconsistent running I experienced in 2018. After some really up and down results, I decided to start tracking when my period comes and how that relates to how I’m feeling in races or training.

I only have a small amount of information at this point, because I’m only using races from 2018 and the start of 2021. But I mostly seem to struggle most in the one to five days before I get my period. I’ve started to recognise the feeling. I might be running a fast pace to begin with, but it feels much harder than it should. I feel like I’m breathing heavier than I should be for the pace I’m running. It doesn’t take long before I’m slowing down with a feeling of heaviness in my legs and really nothing I can do about it.

I first remember that specific feeling during the Gold Coast half in 2018. I was attempting to run my second sub 80. It was humid that morning, and I probably put it down to that at the time. In the first few kilometres, I was running just over 80 minute pace and it felt much harder than it should have. I felt like I was out of breath. I ended up slowing down and finished in about 82 minutes. I got my period 4 days later.

In the three weeks that followed, I ran my fastest 5km for the year, and my best race of the year which was a hilly 4km as part of a road relay. I felt great at both.

Then one week after the road relay, I ran the Sydney Harbour 10km. Once again felt like I was working too hard early on and ended up walking. I got my period the following day.

I didn’t do much racing after that in 2018.

After my cycle returned at the end of 2020, I noticed the feeling I described from Gold Coast and Sydney Harbour 10km at parkrun on Christmas Day. I started out at a decent pace, with a 3:29 first kilometre, but it felt like hard work. It is essentially my PB pace for 5km, but I would still expect it to feel okay for the first kilometre of a race. I was breathing quite heavily, and gradually over the following kilometres, my pace dropped off. The last kilometre, I felt like my legs were really heavy and I had dropped down to about 3:53/km pace.

The next month I was prepared for it, and started out slower at parkrun for a more consistently paced (but still hard) run.

Then in March, I had Six Foot Track. I was expecting my period about 4 days after the race. I was hoping that I might be lucky and it wouldn’t be an issue. Maybe it would come a bit late, and maybe since I wasn’t going to be running fast (in road running terms) it would be okay.

It definitely wasn’t okay.

Once again, I could tell within a few kilometres that I was breathing heavily and didn’t feel comfortable at the pace I was running. I saw my family at 8km and thought about stopping there. I knew I was working far too hard. And there was a long way to go. The downhill section that followed, I perked up a bit and thought briefly that I might bounce back. But as soon as I hit the hills, which I ran up fairly comfortably in training, I had nothing. I felt like I had lead in my legs and it didn’t get any better from there. I walked up the majority of the hills, and ran/walked the rest of the way to the finish.

I got my period the next day.

To say I was frustrated was an understatement. I had trained well, not great but still enough that I thought I would at least be able to run my C goal. In the end I was over 20 minutes behind that. I had spent a couple of years I spent thinking about this race, after withdrawing due to pregnancy and then the race cancellation in the aftermath of the bushfires. After such a long build up, I really wanted to do well. The timing was definitely not ideal.

Which brings me back to what to do if a goal race falls in the part of my cycle where I seem to struggle.

I’ve started talking about this to more and more running friends and have been on the hunt for any information I can find. There is this Instagram post and this Instagram post that are quite informative, and I’ve started reading the book Roar by Stacy Sims. One interesting point I’ve taken from the book so far is why the higher levels of estrogen at the end of the cycle have an impact. It turns out that estrogen causes your body to save glycogen and prioritise fats and protein for energy. It’s a slower process to convert fats to energy than it is to convert glycogen to energy, and requires more oxygen. This is not ideal if you’re doing a fast race that requires you to operate in the higher portions of your aerobic capacity, because you need energy quickly and need to use oxygen efficiently. By prioritising the form that fuel that is slower to convert to energy and requires more oxygen, it’s definitely not efficient.

This could explain why I feel like I’m breathing heavily when I race close to my period arriving. If my body is sparing the glycogen in favour of fats and protein, it would need more oxygen. My lungs are probably trying to keep up with the demand and as a result, my breathing rate increases.

I hope there is some info to come in the book on what to do when your race falls in that part of the cycle. So far this year, I have entered a few races and checked the dates against my app that tracks my cycle. It's been frustrating to see a few clashes between the two. The Instagram posts I linked above suggests certain types of foods that are more helpful in different parts of your cycle, which might be a starting point for me to try.

Because aside from that, at the moment it seems like the best solution for me is to go back on the pill when I’m done having kids! The last thing I want is for when I get fit enough again to aim for a marathon PB, is that it falls in the wrong time of my cycle.

Image of me training for Six Foot Track
Mid training Six Foot Track training run, feeling awesome after just running up most of Pluvi. Too bad this wasn't race day!

Image of the high hormone phase of your menstrual cycle
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