Healthy cycle despite top-level sport: Yvonne van Vlerken recommends carbohydrates, warns against fasting training and the pill. She is most concerned about amateur athletes.

Yvonne van Vlerken (fourth from right) with her training group. One of the important topics in coaching is periods.

Yvonne van Vlerken (fourth from right) with her training group. One of the important topics in coaching is periods.


Yvonne van Vlerken, you were a professional triathlete for 20 years, won an Ironman 16 times, set a world record in the long distance, and were world champion in duathlon. What do you regret?

I wish I had known earlier that it wasn’t okay to miss a period. During most of my career, I only had one a year. The doctors told me it wasn’t that bad, it would come back at some point. But periods are part of being a woman, they are a sign that your body and mind are healthy.

So you were in top shape but still unhealthy?

Yes, I treated my body incorrectly for years. I ate too little for the amount of training I did and was in an energy deficit every day. At some point I took it for granted that I no longer had my period. As a top athlete, I had no idea how important a regular cycle was for my health. If you don’t have your period for years, the risk of osteoporosis increases and your desire to have children can remain unfulfilled.

Yvonne van Vlerken was one of the world's best triathletes. She lives with her partner in Leipzig.

Yvonne van Vlerken was one of the world’s best triathletes. She lives with her partner in Leipzig.


You speak openly about a topic that affects many athletes; endurance athletes are particularly at risk. In your opinion, how common are disrupted cycles?

An incredible number of women are affected by this. I have observed this myself over the years: I coach triathletes – dozens of them had irregular cycles, some of them stopped having periods altogether. When I talk about the topic in podcasts or write articles, the response is huge, so many affected women contact me. But as much as I would like to, I can’t help everyone.

According to a British study, a third of professional female athletes ignore a missed period. This is partly because doctors say it is normal when a woman does so much sport.

It’s a joke when doctors say that your period will only come back if you stop exercising and gain ten kilos. That’s one way, but not the only one. It’s about getting your energy balance right. Of course, you can reduce the intensity of your training and rethink strict units. But if you forbid women from exercising, you forget how important it is for them. Many need it as a way to balance things out; they release endorphins; exercise makes them happy.

Who is affected by missed periods: amateur athletes or professional athletes?

Both. But amateur athletes are often even more at risk. Let’s take the example of an ambitious amateur triathlete: she trains up to 20 hours a week, gets up at 5 a.m., rushes to the swimming pool, hardly eats breakfast, works until 5 p.m., and wants to get on her bike afterwards. A professional athlete has a team that looks after her and the time to eat well and relax three times a day. A woman with a full-time job and family doesn’t have these opportunities.

You were a professional. How did it get to this point?

In 2007, I moved from the Netherlands to Vorarlberg. I left my home behind – and my period. I trained 30 hours a week. During training, I was surrounded by men; my closest training partner was my boyfriend at the time. He suffered from an eating disorder, and his disordered eating habits soon rubbed off on me: instead of bread rolls, I ate vegetables, fish, cottage cheese, cheese, and nuts. I was missing carbohydrates. From then on, my period only came in December during the competition break, and I bled two days a year. I didn’t talk to anyone about it, not even my trainer. Back then, we knew so little about the influence of the cycle on athletic performance.

Yvonne van Vlerken at the Leipzig Half Marathon 2024.

Yvonne van Vlerken at the Leipzig Half Marathon 2024.


In female athletes, the so-called relative energy deficit can lead to hormonal disorders, estrogen and progesterone levels drop, and periods stop.

That’s what happened to me too. My body got the signal that I was not capable of getting pregnant. My entire reproductive system shut down. I was like a heater on standby mode. My body temperature was 35.5 degrees, my resting heart rate was around 30. I was proud of my heart rate, attributing it to my athletic performance. My estrogen level was low, the hormone is important for bone density in women – anyone else would have suffered stress fractures, I was never injured. My bone density was good due to years of strength training, as was my muscular condition. I felt great, ran top times. That was the strange thing.

How did you sense that something was wrong?

Suddenly I developed terrible symptoms. I was dizzy, sweating, constantly tired, had trouble recovering, and looked haggard. The doctors had no idea. It was only my Dutch sports doctor who came up with the idea that my problem might be hormones. I then had my levels tested: the estrogen and progesterone were no longer there, and the hormones FSH and LH were very high. The levels were similar to those of a 60-year-old woman. I was at the beginning of my menopause, but I was only 38 years old.

What happened next?

In 2019, I retired because of the symptoms; I felt so sorry for my body. On top of that, my partner and I wanted to have children. We would have loved to become parents. So at 40, I tried everything to get my period back. I stopped running for four months and gained eight kilos. My period came back. However, the quality of my eggs was poor and I couldn’t get pregnant. Then the last egg matured and I was still childless. As a professional athlete, I was always in control of my performance, but this time I was powerless. It was frustrating.

Did early menopause have anything to do with your missed period? There is no scientific evidence for this.

No, it is not. But the topic has not been researched much, and I believe there is a connection. Especially since my mother went through menopause at 50, and I went through menopause twelve years earlier.

How are you today?

I have been taking hormones for two years, half the minimum dose. This simulates a cycle. It is a very personal decision, but for me it is right. I had terrible symptoms before. I looked bad, sweated so much that I had to change my bedsheets and pajamas several times a night. Now I can sleep for ten hours straight and I can walk again.

Today you are a trainer and coach professional and amateur triathletes from Germany, Austria and the Netherlands. One of the important topics in training: the female cycle.

It is much easier to train a man. For women, everything is much more personal; there is no standard training program that works. But if women know their cycle, it is extremely beneficial. They are less prone to injury, understand their bodies better, and know that certain sessions are pointless at certain times, for example hard running sessions just before their period.

Do you talk to women about missed periods?

When an athlete contacts me, the first thing I ask her is how her cycle is. Many have irregular cycles, and some have stopped having periods altogether. My goal is to help everyone get a healthy cycle back. If they haven’t overdone it for years like I have, simple measures are often enough. With one exception, everyone on our team has a healthy cycle again.

How do you do that?

There should never be an energy deficit; the body should not use more energy than it receives from food and drink. Training on an empty stomach is absolutely forbidden. I did it for years and loved it. Men can benefit from it, but it is often bad for women’s hormonal health. The body releases stress hormones and estrogen levels drop. Another mistake is to cut out carbohydrates. A low-carb diet is not possible for most women; it means additional stress for the body. It is also important to eat something within 30 minutes after training. Women have a smaller window of time to get energy than men.

What do you think about the pill?

I don’t coach any athlete on the pill. Any hormonal imbalances are covered up by the pill; bleeding always occurs, it is artificial. In addition, the hormones in the pill reduce performance. I have convinced the women in my training program to use non-hormonal contraception. None of them have regretted it.

You adapt the women’s training plans to the phase of their cycle. How does that work?

I note each athlete’s period and ovulation in the training calendar. I adapt the plan as I go, because many have irregular cycles. Not everything is as it should be in a textbook; you don’t have to worry if your cycle lasts 32 days instead of 28. For athletes who don’t have period pain, I plan intensive cycling sessions from day 1 of menstruation. In the first two weeks up until ovulation, women’s hormones are low, most similar to men’s hormone levels. I then focus on hard and fast training. Around ovulation, some athletes can run their personal bests, others are very tired; training is individual. In the second phase of the cycle, I reduce the intensity and focus more on endurance and technique.

The competition may take place at a time that is not ideal for an athlete. For example, shortly before the period. Many women then feel exhausted, bloated and heavier.

Yes, unfortunately that is the case. With professional athletes, I therefore try to choose the date of an important race so that it falls in a phase of their cycle that is favorable for them. However, a competitive situation can compensate for an unfavorable phase of their cycle. The athlete is well rested, has eaten well, and the atmosphere is great.

What advice do you have for recreational athletes who go jogging twice a week?

I advise athletic women of a healthy weight not to train on an empty stomach. There is no excuse; a muesli bar or two rice cakes are enough as a small breakfast before training. Cycle-oriented training is very individual: some women hardly have any problems, others feel the hormonal changes strongly. The most important thing is that every woman records her cycle and observes how she feels.

For a long time, periods were a taboo subject, especially in sports. How much awareness is there today?

It has grown over the past five years; among professional athletes, amateur athletes, but also among coaches. At an advanced training weekend organized by the Austrian Triathlon Association on periods in sport, many male coaches took part in my workshops. They now know how much the cycle affects the performance of athletes. A woman who trains according to her cycle feels better and is less likely to get injured. She is a happier and often more successful athlete.

You only recently acquired this knowledge. Your career could have turned out differently.

If I had known more about my cycle earlier, I would probably have done even better. This year in Leipzig I broke the event record and my personal best in the half marathon, running the course in 1 hour 16 minutes. And I was 45 years old! I am happy with my career and grateful for everything my body has achieved. But I want to spare other women my suffering.

Former world record holder

ยท Yvonne van Vlerken is a Dutch triathlete and duathlete. The 45-year-old has won 16 Ironman competitions; in 2008 she set the then world record over the Ironman distance at the Challenge Roth with 8:45:48. Van Vlerken retired in 2019. Since then, she has dedicated herself to coaching professional and amateur triathletes with her training group Vonsy’s Tri Family. She lives with her partner in Leipzig.