The limits of the human body over the marathon: “We haven’t explored everything, and surprises are still possible,” says Guillaume Millet

✓ An interview with Guillaume Millet, whose perspective goes beyond simple numbers and performances.

What does physiology involve, and what can it contribute to the race for records and ever-greater performance?

Exercise physiology is the study of how the human body functions while moving. We study the body’s acute responses to exercise and its chronic adaptations to training. We try to understand how it reacts. In a way, we study the limits of the body. Physiology can, for example, help athletes and coaches assess the factors that determine performance.

What does it take to run faster and longer?

That isn’t possible. It’s one or the other. Running fast and running for a long time require diametrically opposed qualities. If we focus on marathon speed, you need a high VO2max, which means a powerful heart and blood rich in red blood cells, and the ability to sustain a high percentage of that VO2max over the distance. In other words, you need a big engine and you have to keep it running at high revs for 42.195 km. Staying with the car analogy, it’s also important to have low fuel consumption, meaning that you use energy economically. For runners, we talk about energy cost, which depends in particular on biomechanics and equipment.

 There have been, and will always be, improvements. Every parameter is optimized and scrutinized with the aim of improving performance.  

Are men and women competing on an equal footing?

No. The main reason is that women have a lower VO2max than men. The best women will never beat the best men. On top of that, even the leanest women have a higher body-fat percentage than the leanest men. In the marathon, the women’s elite will never surpass the men’s elite, although that doesn’t stop women from closing the gap as the distance increases.

In 2019 in Vienna, Eliud Kipchoge achieved the feat of breaking the two-hour marathon barrier in 1:59:40. Without the outside assistance, such as the closed course and pacemakers, could he have set that record?

No, because the drafting setup he benefited from was truly optimal and meticulously planned. It was carefully designed: he was surrounded by pacemakers who shielded him from the wind, and he received drinks from a bicycle, so he didn’t lose time slowing down at aid stations. It’s estimated that the entire setup saved him well over the 20 seconds separating his time from the two-hour mark.

Are African athletes more physically predisposed to running faster?

This is still debated within my profession. They dominate the marathon world to an extraordinary degree. In my view, there is already a cultural factor. In Africa, athletics has a central place. Athletes there are treated like Zidane is in France. That factor means they train more. I find it hard to believe there is no physical predisposition. These athletes have low energy costs, and they are often small and slender, with relatively little muscle mass. Altitude may also work in their favor, although that has not been proven. So it’s a combination of factors, not forgetting doping, which could unfortunately also help explain some of this dominance.

Can equipment, nutrition and other factors still be improved today in the hope of seeing new records?

We haven’t explored everything, and surprises are still possible. Take shoes: who would have thought ten years ago that so much time could be gained from super shoes? Nike eventually released its Vaporfly 4 with a new carbon-fibre plate, but above all a new material and a new shape. Tomorrow, we will certainly have even better shoes. The same goes for nutrition. Energy gels on the market now allow athletes to consume more carbohydrates per hour. There have been, and will always be, improvements. Every parameter is optimized and scrutinized with the aim of improving performance. Obviously, every second becomes harder and harder to gain, but times will continue to come down. The big topic in the marathon right now is durability, or resilience. In other words, how can you sustain a higher percentage of your VO2max over the marathon, and how can you limit the deterioration in your energy cost as fatigue sets in?

Should we be pleased to remain locked in this perpetual race for records?

It’s a philosophical question, and in my view the answer isn’t clear-cut. If we look at it through the lens of the pursuit of records and the constant drive for more that we see in our consumer society, I don’t think it makes much sense. But if we consider the advances that can benefit the greatest number of people, the picture is different. In the race for records, work on improving certain parameters can also serve medical research. Everything we do to optimize training can help patients who also need to engage in physical activity to improve their health. In that sense, the pursuit of records is useful. Finally, for some athletes on an individual level, chasing records can provide social status and prize money that supports their families. Can we really blame them for that?

Are there risks in wanting to run ever faster and farther at all costs?

Yes. Elite sport is not the best route to optimal physical and mental health. To be in the best possible health, you need to do a lot of sport, or rather a lot of physical activity, up to two hours a day. Chasing records is something else: we’re talking about the 1% of the population who can train for five or six hours a day. But let’s remember that the risk of doing nothing is far greater than the risk of doing too much sport.

What projects are you currently involved in?

My work, along with that of my team, focuses on fatigue in patients and on how physical activity can help combat that fatigue, even if that may seem counterintuitive. In running, we’re comparing the fatigue caused by trail running with that caused by the marathon. At the same time, the major project driving me is called “0 to 100” and will launch by this summer. We plan to recruit 20 sedentary women and 20 sedentary men and train them over 18 months to reach the start line of the UTMB’s CCC race, the Courmayeur-Champex-Chamonix: 100 km and 6,050 m of elevation gain. By tracking their physical and mental transformation, the aim is to demonstrate that taking up sport can lead to much better health. Casting should begin in the autumn. Right now, we’re looking for partners to complete our budget.

Guillaume Millet’s work does more than push back the boundaries of athletic performance. It also opens up new possibilities for public health. Through training optimization, research into fatigue and innovative projects such as “0 to 100,” he shows that the pursuit of performance can improve overall well-being, both for elite athletes and sedentary people. It is a powerful reminder that physiology research is not limited to records, but can also contribute to public health and progress for everyone.

✓ Guillaume Millet’s website: www.kinesiologui.com