My husband started training with me two years ago and we decided to run a half marathon together. At the time, I was a more experienced runner than he was, so I slowed down and stayed back to keep at his pace throughout that first race, and ultimately I finished stronger than he did.
Then something strange happened… During our next half marathon race, a mere six months later, he was pushing me to run faster and he ended up crossing the finish line a whole minute quicker than me! Three months after that, we ran yet another half marathon and he finished that race an incredible eight minutes faster than me!
It’s worth pointing out that my times did improve steadily with each race but my rate of increase was quite conservative compared to the rate at which he improved. As you can imagine, this was super frustrating, especially considering I trained more consistently than he did! Even now, when he takes a few weeks off, he seems to easily regain his fitness and get back to running faster than I do even with virtually no training.
Women’s participation in running has skyrocketed since the 1980s and most races these days have around 50% female participation. However, on average men in similar training groups still consistently perform about 10% better than their female competitors.
The 2019 London Marathon was won by Eliud Kipchoge with a time of 2:02:37. The female winner, Brigid Kosgei, finished 16 minutes slower with a time of 2:18:20. There were 30 men in that race that finished with a better time than the fastest woman.
So what makes male runners faster than their female counterparts? How does our unique physiology as women affect our running performance? And should women train differently to men?
The Cardiovascular System
Your heart, lungs & blood vessels make up one cohesive system that works together to transport oxygen around your body, which in turn provides the energy and nutrients your tissues need to function.
For runners, sufficient oxygen supply to your muscles is one of the main factors that determines how far you can run at any particular speed. As long as your muscles are getting enough oxygen they can keep working and you can keep running. However, oxygen intake is limited and has a threshold. When your cardiovascular system can’t keep up, you fatigue and eventually have to stop running.
The measure of how well your cardiovascular system can supply oxygen to your muscles is called VO2max (literally meaning the maximum volume of oxygen you have). It is considered the most important factor in determining how fast anyone can run a marathon.
Males tend to have a higher VO2max than their female competitors in the same training levels. For example, elite male marathon runners have VO2max levels around 75-80 ml/kg/min whereas elite female marathon runners have VO2max levels around 65-70 ml/kg/min.
This means that men receive more oxygen to their muscles when exercising and can therefore run faster for longer.
The reasons why men have a higher VO2max is:
(1) men have larger hearts that can pump more blood with each beat
(2) men have a higher concentration of hemoglobin (the oxygen carrying blood cells)
(3) men (on average) have more lean muscle and less body fat which is optimal from transporting and absorbing oxygen.
A key factor that determines your VO2max is your body fat percentage and proportion of lean muscle.
As children, boys and girls have very similar body proportions and distribution of muscle and fat. But with puberty this changes rapidly, – boys gain size by getting more lean muscle, while girls gain size more from fat than muscle.
Adult females tend to have a higher percentage of body fat compared to males of similar stature.
In fact, females need more body fat in order to be healthy and function optimally.
While males require only 2-5% body fat to maintain a high level of health, females need at least 10-13% body fat to be healthy.
Fat is essential in lots of areas of our body including around our nerves, brain, heart, lungs, liver, and glands. Fat plays a vital role in keeping us alive and healthy – it’s used to give cells energy, to help proteins do their job, and to start chemical reactions necessary for immune function, reproduction and other basic metabolism.
Women’s anatomy and physiology requires more fat to function properly; we have breast tissue as well as more fat around our pelvis and reproductive organs. But from a running perspective, this extra body fat slows down oxygen absorption during long distance running and means that women are at an inherent disadvantage compared to their male competitors.
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Arguably, the biggest difference between male and female runners is our hormones.
Hormones are extremely influential in how your body functions. They control a lot of what goes on in your body by acting as ‘messengers’. They travel all over the body and tell specific cells to do certain actions. They affect everything from your digestion to tissue growth, immunity, reproduction and a whole lot more.
Estrogen and testosterone are the two most significant hormones when it comes to the difference between male and female runners. While both men and women have both of these hormones in their body, the amounts of each are significantly different.
Males for example have about ten times more testosterone than females. And females have significantly more estrogen than men. This affects not only how we look, but also how our bodies function.
While these hormones are best understood for their role in reproduction and sex, they also affect lots of other bodily functions and play a role in how you feel and perform during a run.
Estrogen is a really important hormone for females. Aside from regulating mensuration, estrogen is known to affect bone mineral density, cholesterol production, lung function, body temperature, plasma volume of the blood, and salt & water retention, just to name a few. So as you can imagine, the amount of estrogen you have at any given time can then affect your running performance.
And just to make it more complicated for women, our hormone levels are not consistent day to day. Depending on where we are in our cycle, the amount of estrogen fluctuates. For men, hormones stay pretty consistent all the time.
This means that during some days of your cycle you might find it easier to run faster for longer without getting puffed out. And for some of us there might be optimal days to run races or pursue PBs (although the data on this isn’t conclusive).
Estrogen, while being a very important hormone, is not exactly a performance booster like testosterone is. This is another reason why men tend to improve fitness quicker than women and ultimately why they can run faster.
When running, your muscles need a constant supply of energy to keep working. Energy is made by turning fat or glucose (carbohydrates) into fuel.
The more fuel your muscles have, the stronger they can contract and the longer they can work. So, runners who can produce more fuel can run faster for longer.
While your body can use both glucose and fat to make fuel, the process for turning glucose into energy is considerably quicker, so it’s the preferred source of fuel when running, especially at faster speeds.
If your body uses fat, the energy isn’t available to the muscles as quickly, so they can’t work as quickly meaning you won’t be able to run as fast.
Men have more glucose stored in muscles meaning they have quicker and easier access to this preferred fuel source.
Research has also shown that women tend to rely more on fat for energy production than men. When running at a similar level of exertion of 65% VO2max, women get approximately 39% of their energy from fat while men get 22% of their energy from fat.
Research suggests that this difference between fat vs. glycogen use may be driven, at least partly, by estrogen. Research done on rats has shown that when male rats are given estrogen, the concentration of fatty acids in the blood increases, suggesting a greater availability of fat for energy; and they can exercise for longer periods before becoming exhausted (but are overall slower).
So, because men tend to have more glucose stored in their muscles, and tend to rely on glucose more for energy production, they can make more fuel more quickly for their muscles to use when running. Women have less glucose stored and ready for use, and we prefer to use fat, the process for providing energy to our muscles is slower. This means men get more fuel, quicker than females.
The main reasons that I can’t run a half marathon as fast as my husband can —even when our level of training is the same—is because of my smaller cardiovascular system, greater percentage of body fat, higher levels of estrogen and different fuel production. Given the many differences between male and female runners, women should therefore approach their training and racing differently than men to optimise these unique characteristics.
- Karp JR & Smith CS, 2012, Running for Women, Human Kinetics
- Joyner MJ and Coyle EF, 2008, Endurance exercise performance: the physiology of champions, Journal of Physiology, vol 596. pp 35-44
About the Author
Alina Kennedy is the founder and lead Physiotherapist behind The Runners Physio.
Alina is a physiotherapist and strength & conditioning specialist based in Adelaide, Australia. She graduated from the University of South Australia in 2011 and works as a sports physiotherapist focusing on running performance and injury rehabilitation. She’s developed training and rehab methods based on years of clinical experience and up-to-date scientific evidence. Her simple but effective approach has successfully helped thousands of runners overcome repetitive injuries and get back to running faster and healthier.
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