The Science of the Marathon — Dr. Veronique Billat - A Coaches Physiologist
This article is adapted from the podcast: Nerd Lab: Dr. Véronique Billat – A Pioneer in Interval Training Research and The Science of the Marathon book by Drs. Billat and Edwards.
Interval training and VO2 max is as fundamental to endurance sports training as putting on a pair of running shoes or clipping into a set of pedals. Yet, many of us were born before “interval training” was ever coined. It was only in the 1960s that Per-Olof Astrand started extensively studying interval training in the lab. If you’ve wondered where many of our current beliefs about interval work came from, this is for you.
French researcher Véronique Billat pioneered interval training research in the 1990s and 2000s, at a time when men entirely dominated the field, Dr. Billat, more than almost any other researcher, defined interval training. It’s important to highlight that in an otherwise male-dominated profession, in a field that often tests male subjects, her work is amazing and has been formative in physiology. She’s still publishing and hosting a YouTube channel—BillaTraining.com. What’s important to point out is how vast her research is and how much she’s defined interval training. All of her studies are available on the BillaTraining.com website.
Dr. Billat is “a coach’s physiologist.” This is where the top-level coaches go to add to their training protocols. Her studies deliver understandable and practical information. It’s not theoretical, it’s not acronyms, it’s not biochemistry. There are many take-home messages that coaches directly apply to their athletes. She helped pioneer many innovative ideas, like the importance of spending time at VO2 max and the power of short intervals (like 30-30s). In the case of 30-30s, it’s a workout that many top coaches consider one of their top routines, even today.
We review a few critical studies from Dr. Billat’s illustrious career, starting with her most cited review, Interval Training for Performance: Scientific and Empirical Practice. In this 2001 review, Dr. Billat traced the history of interval work and then raised the question of whether long or short intervals were better for aerobic training. While this notion has long been accepted, it wasn’t always so.
Interval Training for Performance: A Scientific and Empirical Practice – 2001 Review Part One and Part Two
In the 2001 review, she made some interesting points:
Most research was done in the lab, not in real-world conditions.
Most of the research was in running, so a significant number was your velocity at VO2 max. When they did a test, and you determined VO2 max, what velocity were you running at?
The studies were calibrated based on either running at that velocity of VO2 max or running at a percentage of it.
She pointed out that coaches tend to calibrate training based on your running speed in a race.
World records were set only in races, not on a treadmill. Most of the breakthroughs in performance have been in real-world environments.
This review’s is about aerobic interval training, the entire history of interval training, and is her most cited study. The second review articulates what we know about interval training and contains special recommendations for mid— and long-distance running.
Dr. Billat starts with the first-time interval training that was described in the literature in the 1950s. This is interesting because you’d think we’ve been running intervals for a long time; it’s not that long ago that we started thinking about this. Before the 1950s, coaches and physiologists used hills for interval work — run hard up the hill and then recover by coming down.
She details the history of many famous runners, the Olympic champions and the World Champions, through various historical points and shows what interval work they were doing. And consider how much work required to find all that information. It’s a fantastic table, and you can look back through it and see what the top runners in the 50s and 60s were doing.
Another interesting historical fact is that they measured oxygen consumption and figured out the concept of VO2 max in the early 1900s. Dr. AV Hill invented the whole concept of VO2 max.
The concept of anaerobic threshold was introduced in 1967, and it wasn’t meant for sporting purposes but for medical purposes. Researchers started looking at lactate threshold, anaerobic threshold, and all these sorts of things in the ’70s and ’80s.
VO2 max is Central to Everything
Everybody talks about functional threshold power (FTP), lactate, or anaerobic thresholds. So, we’ve made a switch. However, when you look at the history, VO2 max and the concept of VO2 max have dominated the research for a very long time.
The power meter for cycling was invented in the late 1980s and widely used in the 1990s. But as we’ve learned more, we’ve started to say what measures or metrics will predict performance: FTP.
FTP explains more of the variance in performance and the difference in race results better than just VO2 max alone. But everybody recognizes and understands that VO2 max is still essential in determining FTP and isn’t something you can discredit.
It’s essential to understand the history, which was for the longest time was focused on running. And that was because you could put somebody on a treadmill and control velocity; since they knew your velocity at VO2 max, they could set percentages, making it easier to control studies. This is why you hear so little about cycling in these reviews. At the end of the review, she goes through the different endurance sports; she talks about swimming, rowing, and running and doesn’t even cover cycling. Nowadays, most research in endurance sports is done on a cycle ergometer.
Dr. Billat challenged the existing dogma of endurance training and elucidated many nuances of interval training that changed the nature of how we train. At the time of this review, these were new and novel ideas. She broke the training section into three major sections: short intervals, which are essentially 15-15s or 30-30s; then she discussed longer intervals at velocity at VO2 max; intervals in the five-to-eight-minute range, as long as you can hold a high workload. Third, she discussed very long intervals at intensities between the maximal lactate steady state and the velocity of VO2 max. But ultimately, we’re still talking about relatively short intervals.
Why 30-30s are So Important
So, let’s dive into the short-interval side of things. I will tell you from experience that 15-15s or 30-30s are not as easy as they sound. Perform three sets of eight minutes with a 10-minute rest in between, and you will limp home from that workout. The idea of doing 15-15s for an hour is dreadful.
Dr. Billat’s research highlights the differences between short and longer intervals. What’s interesting is the level of lactate that the body experiences between them. In that longer interval, the four-to-six-minute interval, the body produced lactate of about ten millimolars, which is very high in the scheme of things.
The short 15-15s efforts were averaging about two millimoles of lactate. TWO mmols of LACTATE! Two mmol of lactate is barely above baseline in the whole scheme of things and solidly within zones 2 and 3. It’s unbelievable that there was so much difference, but repeatedly, she talks about different studies that cite the same results. This is why Dr. Billat favors short intervals: You limit lactate increase and spend more time at VO2 max.
On the glycogen depletion side, longer intervals deplete the glycogen in the type two muscle fibers. She proposed that the shorter intervals, the 15-15s, were much more taxing on the aerobic system and, therefore, better for training. Shorter intervals allow oxygen to recharge in the muscle’s myoglobin, and you could regenerate some creatine phosphate.
You are ultimately avoiding the anaerobic contribution that the long intervals require because the long intervals burn through all your ATP, creatine phosphate, and oxygen, pushing you into an anaerobic situation; eventually, you hit the infamous wall and bonk.
Dr. Billat talks a lot about myoglobin stores. It’s an exciting concept. For those unaware, most have heard of the term hemoglobin, which are cells floating in your bloodstream delivering oxygen to all your tissues, not just your muscles. Myoglobin, the Myo, meaning muscle, is essentially like hemoglobin, which is locked inside the muscle and holds onto and delivers oxygen.
When we talk about anaerobic energy production, it’s constantly pointed out that you have a store of ATP in muscle cells. So, you can exercise for several seconds just on that store of ATP. This is the aerobic equivalent: myoglobin already has oxygen bound to it. So, you have this availability of oxygen that you can use before you must start delivering oxygen. Dr. Billat says myoglobin provides oxygen directly for about half of the 15-second intervals based on the stores in the muscle itself. Then, it can be recharged in frequent rest periods. Improved running economy is one factor that allows you to run faster. Short intervals, as opposed to long threshold runs, helps optimize running economy. Another way to think about it is doing more work for the same amount of oxygen. So, the idea is that if you do those longer, four-minute intervals, you deplete the oxygen in myoglobin. But with the 15-15s, myoglobin can at least partially restock its oxygen.
Fat Burning and 30-30s
Even more mind-blowing to many people is that lipid oxidation was higher in the 15-15s as opposed to the four-to-six-minute intervals. So, you have this great scenario where you spend significantly more time at or close to VO2 Max; you’re not accumulating lactate. You’re burning more fat, which is amazing.
The 30-30 Prescription
We talk a lot about the 30-30s, but we often don’t necessarily talk about the actual prescription of 30-30s, and it is overwhelmingly important that that recovery is active. She found that being at 50% of your peak or your “hard perception” workload was about the right place and that you can get enough recovery to continue doing this one after another. But you’re also keeping that oxygen consumption high throughout the recovery period. In the research paper, she pointed out that they could study up to eighteen 30 -30 efforts in a row. Subjects were hitting the VO2 max at about the fifth interval and maintained VO2 max from the fifth to the 18th interval; this is about 85% of the time spent at VO2 max. That is about as high as you can get.
To point out the opposite, when we talk about the longer intervals at 100% of the velocity or the power at VO2 max, an interval where you’re doing four to six minutes of work, it takes multiple minutes to get to VO2 max. So, you might be doing that for five minutes. But you might not hit VO2 max until three and a half minutes in, which means that out of that five-minute effort, you only get a minute and a half at VO2 max. Whereas in those 30-30s. If you’re able to continue knocking them out, then you’re able to maintain that level. And because you’re not depleting all the stores like you are in the long effort. You don’t need the long recovery like the long efforts require.
In the Science of The Marathon, we talk about long intervals, such as constant paced training, and that you don’t improve your time at VO2 max and accumulate a ton of lactate. The adaptations we see from short 30-30 intervals are magical. Long intervals involve a whole lot of pain and lactate accumulation, and you don’t spend a lot of time at VO2 max. Hopefully I’ve said this enough, because it’s an important point.
Finally, it’s possible to do 30-30s wrong. An inappropriate 30-30 workout prescription is that if you allow complete rest, you’re not taxing that VO2 max and, therefore, not getting the benefits.
Overtraining
The overtraining paper showed that with at least twice the high-intensity work, but did not see improvements in VO2 max. The study showed an increase in norepinephrine after an exhaustive workout. Their subjective rating of soreness was very high. However, the key is that there was no further improvement in their velocity at VO2 max. They maintained what they achieved during the normal training and didn’t improve any further. But you also didn’t see that decline in performance that you would expect from being overtrained. The takeaways are that you can get impressive improvements from the standard workouts, and additional training is only sometimes better. Granted, there was an increase in norepinephrine, but there weren’t the other changes that you would expect to see in an acute sense with overtraining: maximal heart rate stayed essentially the same, maximal lactate stayed essentially the same or a decrease in maximal lactate. A decreased lactate indicates an athlete is heading off into an overtraining state.
Individualization of Training Programs
When Training Peaks software came out in the late ’90s, individualization was rare and everybody was prescribed the same training zones. Coaches prescribed a lot of 5 minute intervals. This is where individualizing VO2 max relative to power thresholds changed how athletes trained.
Dr. Billat points out that many coaches at the time would do regular training for a while, then a four-week overload with their athletes ahead of the season to get those last little gains, and then they would rest the athlete and take them into the race season. She did her tests after the four-week overload only a week later.
This touches on the topic of super-compensation. We know that when somebody does hard work, their performance immediately decreases. For example, you did a hard workout yesterday and then did a maximal test today; you’ll probably be worse for it.
Lactate and performance is anything but straightforward
A 1996 review, Use of Blood Lactate Measurements for Prediction of Exercise Performance and Control of Training, showed how early the research on blood lactate physiology was in the 1990s. At that time, VO2 max—and not FTP—reigned supreme.
There’s much controversy around blood lactate, which Dr. Billat points out. We don’t know if it’s physiological. This is where coaches like Dr. Inigo San Milan cringe in his office because, for them, everything’s about lactate. If he could create a lactate meter on the road, he would throw power, speed, heart rate, and everything else in the trash.
There are two states: sustainable low intensity, where lactate doesn’t accumulate, where you are producing your aerobic energy, and then you hit a certain point, which she calls the anaerobic threshold, and that above your anaerobic threshold, it’s no longer sustainable. You’re accumulating lactate, and that’s because you’re bringing in glycolysis to produce energy. Today, we know this concept is outdated because we are using all these different energy systems simultaneously.
Also, exercise is limited by the increase in the internal temperature associated with dehydration, which is prevented by the supplementation of water and substrate. High or maximal acidosis causes exhaustion and fatigue by disturbing the internal biochemical environment of the working muscle and the whole body.
Lactate accumulation doesn’t correlate with VO2 max. They’re two different things that you’re measuring, and they don’t match up. So, when you think about that, we have this lactate threshold and this VO2 max, but your using two different systems to identify them, and those two systems don’t fully correlate. You’re mashing apples and oranges together to develop training zones.
We can’t necessarily define what we would otherwise call the VO2 max by a lactate measure. For some people, that’s six millimoles. For some, it’s at seven. It’s not like we can identify something on a curve like we can on the lower part of the profile. And so, you’re almost forced into doing that. But it is important to note that we’re measuring two different systems.
VO2 max is based on oxygen delivery and lactate accumulation, while the lactate threshold is based on glycolytic flux. One is aerobic, and the other is anaerobic. The lactate threshold improves within two to three weeks in untrained individuals. Ultimately, slow twitch muscle fiber count contributes to the lactate threshold.
Children and VO2 max
Children produce significantly less lactate than adults do. Many assume that children are more anaerobic than they are, with low levels of lactate production. Many thought it was pointless to train pre-pubescent kids in endurance sports because they don’t develop that system until after puberty. But she’s pointing out that children are absolute aerobic animals. And after they hit puberty, then lactate shoots through the roof.
Kids run and ride bikes, primarily for fun. Researching kids is easy. Give them candy as a reward, and they’ll do anything you ask. A maximal test for a child is just a pack of gummy bears slightly out of reach. Kids physiology is different, and many coaches have no idea how to train kids. For one, their lactate levels are entirely different. About two and a half millimoles and children equate to about four millimoles for an adult. This concept of the four-millimole is a threshold, often called the onset of blood lactate acid. In this review, she points out another metric, maximal lactate steady state (MLSS) are essential if you take serial lactate measurements over time at one workload, meaning you go out and ride at 200 Watts. You test it for five minutes, 10 minutes, and so on, and you stay at 2.2 millimoles the entire time, then you bump that up to 220 Watts, and then you test, and and it keeps climbing, then you’re above that MLSS. Dr. Billat points out that maximal lactate steady state can occur between two and seven millimoles of lactate. Traditionally, we consider the lactate threshold in the three-and-a-half to the four-millimolar range. Her point is that lactate is all over the place and anything but straightforward.
She also discusses differences in women. She points out that you don’t see differences in women regarding the percentage of VO2 max and mitochondrial density. Still, women have a superior running economy and higher aerobic tolerance. They use fat metabolism more efficiently and can tolerate higher pain thresholds in relation to the amount of lactate produced.
Master’s Athletes
For Masters, athletes’ lactate as a percent of VO2 max can increase. And it’s not necessarily for good reason. It’s because we’re able to maintain our lactate threshold better than we can maintain our VO2 max. As we age, the VO2 max decreases, and the lactate threshold is less. And the percentage looks better. Dr. Billat points out that this is why you can see athletes in their 40s who can’t match younger competitors in a three-minute effort. But if you put them in a 30-minute trial, you can still perform world-class.
References
Billat V, Poinsard L, Palacin F, Pycke JR, Maron M. Oxygen Uptake Measurements and Rate of Perceived Exertion during a Marathon. Int J Environ Res Public Health. 2022 May 9;19(9):5760.
Billat V, Palacin F, Poinsard L, Edwards J, Maron M. Heart Rate Does Not Reflect the %VO2max in Recreational Runners during the marathon. Int J Environ Res Public Health. 2022 Sep 29;19(19):12451.
Molinari CA, Palacin F, Poinsard L, Billat VL. Determination of Submaximal and Maximal Training Zones From a 3-Stage, Variable-Duration, Perceptually Regulated Track Test. Int J Sports Physiol Perform. 2020 Mar 15;15(6):853-861.
Giovanelli N, Scaini S, Billat V, Lazzer S. A new field test to estimate the aerobic and anaerobic thresholds and maximum parameters. Eur J Sport Sci. 2020 May;20(4):437-443.
Billat, L. V. (1996). Use of Blood Lactate Measurements for Prediction of Exercise Performance and Control of Training. Sports Medicine, 22(3), 157–175. Retrieved from https://doi.org/10.2165/00007256-199622030-00003
Billat, L. V. (2001). Interval Training for Performance: Scientific and Empirical Practice. Sports Medicine, 31(1), 13–31. Retrieved from https://doi.org/10.2165/00007256-200131010-00002
Billat, L. V., & Koralsztein, J. P. (1996). Significance of the Velocity at V̇O2max and Time to Exhaustion at this Velocity. Sports Medicine, 22(2), 90–108. Retrieved from https://doi.org/10.2165/00007256-199622020-00004
Billat, L. V., Koralsztein, J. P., & Morton, R. H. (1999). Time in Human Endurance Models. Sports Medicine, 27(6), 359–379. Retrieved from https://doi.org/10.2165/00007256-199927060-00002
Billat, V L, Flechet, B., Petit, B., Muriaux, G., & Koralsztein, J. P. (1999). Interval training at VO2max: effects on aerobic performance and overtraining markers. Medicine and Science in Sports and Exercise, 31(1), 156–63. Retrieved from https://doi.org/10.1097/00005768-199901000-00024
Billat, V., Palacin, F., Poinsard, L., Edwards, J., & Maron, M. (2022). Heart Rate Does Not Reflect the %VO2max in Recreational Runners during the marathon. International Journal of Environmental Research and Public Health, 19(19), 12451. Retrieved from https://doi.org/10.3390/ijerph191912451
Billat, V., Petot, H., Karp, J. R., Sarre, G., Morton, R. H., & Mille-Hamard, L. (2013). The sustainability of VO2max: effect of decreasing the workload. European Journal of Applied Physiology, 113(2), 385–394. Retrieved from https://doi.org/10.1007/s00421-012-2424-7
Billat, Veronique L., Richard, R., Binsse, V. M., Koralsztein, J. P., & Haouzi, P. (1998). The VO2 slow components for severe exercise depend on the type of exercise and are not correlated with time to fatigue. Journal of Applied Physiology, 85(6), 2118–2124. Retrieved from https://doi.org/10.1152/jappl.1998.85.6.2118
Billat, Véronique L., Sirvent, P., Py, G., Koralsztein, J.-P., & Mercier, J. (2003). The Concept of Maximal Lactate Steady State. Sports Medicine, 33(6), 407–426. Retrieved from https://doi.org/10.2165/00007256-200333060-00003
Billat, Véronique Louise, Palacin, F., Correa, M., & Pycke, J.-R. (2020). Pacing Strategy Affects the Sub-Elite Marathoner’s Cardiac Drift and Performance. Frontiers in Psychology, 10, 3026. Retrieved from https://doi.org/10.3389/fpsyg.2019.03026
