The VO2max Record That (Probably) Wasn’t

Plus bone health for cyclists, freediving physiology, and the trouble with a recent exercise/longevity study

The talk of the endurance world last week was Norwegian triathlete Kristian Blummenfelt’s Instagram post, which offered a peek at the screen following a treadmill test that appeared to show a record-setting VO2max value of 101.1 ml/kg/min. That’s such an impossibly high number that a lot of scientists figure it must be, well, impossible.

VO2max measures how much oxygen you can inhale, deliver to your muscles, and use; it’s the gold-standard quantification of aerobic fitness. Back in 2019, I wrote about a journal article reporting a new VO2max record in another Norwegian athlete, the cyclist Oskar Svendsen. His reading was 96.7 ml/kg/min, eclipsing the previous unofficial record of 96 ml/kg/min set by yet another Norwegian athlete, cross-country skier Bjørn Dæhlie, in the 1990s.

Blummenfelt’s value has only been reported on Instagram, where peer review can be vicious but isn’t known for rigour. Numerous scientists have posted their own opinions of the result, including Jeroen Swart, Jem Arnold, and Stephen Seiler. The key detail many of them zeroed in on: the screen also showed an RER value of 0.93. RER is respiratory exchange ratio, which is the ratio of how much carbon dioxide you’re exhaling divided by the amount of oxygen you’re consuming. With a little math, this ratio tells you how much carbohydrate versus fat you’re burning. It’s also used to confirm that you’ve really reached VO2max, as opposed to giving up early because you’re either unable or unwilling to keep pushing to exhaustion.

In theory, VO2max readings are supposed to reach a “plateau,” levelling off even as you keep increasing the pace. In practice, not everyone’s data shows a plateau before they give up. Physiologists have been arguing for years about how to verify that you truly hit max. One of the criteria sometimes used is RER: it needs to be above (depending on who you ask) 1.00, 1.10, or 1.15. This is because high-intensity exercise starts producing lactate, which sets off a cascade of reactions that produce extra carbon dioxide.

The RER threshold isn’t perfect, because there can be variation in maximal RER values. But in general, if your RER is below 1.00, the assumption is that you quit early and your true VO2 max value is higher. That’s what makes Blummenfelt’s measurement so bizarre: it’s super high, but seemingly should be even higher. Still, human physiology is complex, and champion athletes like Blummenfelt are, by definition, one-of-a-kind. We have no idea what exercise protocol they were using, or whether other factors like dietary manipulations might be affecting the results.

When I was digging into Oskar Svendsen’s value seven years ago, several scientists in Norway expressed the opinion that Bjørn Dæhlie’s previous “record” was a dubious reading that his team had decided to leak to psych out his opponents. Similarly, it’s not hard to imagine Blummenfelt and his team enjoying the furor they’ve kicked up with their Instagram post. But unless their data shows up in a peer-reviewed journal, Svendsen is still the record-holder. Blummenfelt, meanwhile, can console himself with his Olympic gold medal and Ironman world titles—and the rest of us can use the incident as a reminder of which outcomes matter and which ones don’t.

Outtakes

A few quick hits on recent studies that I haven’t written about elsewhere:

The Crazy (and a Little Bit Scary) Physiology of Freediving

I got fascinated by freediving research when I was working on the “oxygen” chapter in Endure. I couldn’t believe that someone could hold their breath for more than 11 minutes, and found the various adaptations the body makes during dives (like squeezing the spleen to release extra red blood cells) very cool. But I also came across some hints that repeatedly depriving your brain of oxygen can have long-term consequences.

A big new review of freediving research in the European Journal of Applied Physiology, from researchers in Italy, brings together the current state of the art on freediving research. There are a bunch of interesting nuggets in there, like the observation of a freediver whose arterial oxygen levels dropped to 25 percent during a deep dive. For context, the values in a group of climbers near the summit of Everest at 8,400 metres ranged between 34 and 70 percent, which were considered “among the lowest ever documented in humans.” But it’s the evidence—still very limited—of neuron damage and lasting cognitive impairment that sticks in my mind.

How Do You Know If Altitude Training Will Work for You?

Altitude training is now considered all but essential for elite endurance athletes, but there are still doubters in the scientific world. The question isn’t whether it works in theory, but whether you can count on it working in practice. Studies tend to find that some athletes return from altitude training camps with a boost in red blood cells, and others don’t, so there’s great interest in figuring out how to predict in advance who is likely to benefit.

That’s the focus of a new study, also in the European Journal of Physiology, in which 15 German national team athletes did three weeks of altitude training by living in an “artificial altitude house.” Blood tests picked up two key pre-camp signals of who would respond best to altitude: healthy immune function (as measured by levels of various types of white blood cell) and iron status (as indicated by a hematocrit above 42.5 percent).

Why Cycling Is a “Perfect Storm” for Bone Health

The UCI, cycling’s governing body, sponsored a major sports nutrition research project, and one of the outcomes was this paper on bone health among cyclists. They suggest that cycling creates a “perfect storm” of overlapping risk factors: the lack of jarring impacts, prolonged periods of calorie deficit, self-selection of naturally skinny people, and more subtle metabolic shifts that occur during prolonged exercise, like a drop in calcium levels that promotes bone weakening. The solution: eat enough to fuel your training, particularly carbs, and also make particularly sure to get enough protein, calcium, and vitamin D. Relatively brief bouts of jump training can also stimulate bone strength.

Sweat Science Columns in Outside

A couple of recent columns:

What the New Study on Exercise and Longevity Really Tells Us: Harvard scientists find that exercise variety is good but not too much and only certain types. Take the findings with a grain of salt.

This is a deep dive into a study that got a lot of attention in both mainstream and social media last week. My key message is about the dangers of “statistically adjusting” epidemiological data to effectively erase the impact of exercise on parameters like BMI, blood pressure, and cholesterol, and why that creates the illusion of a plateau in the longevity benefits of exercise.

The 3 Steps This Year’s Olympic Athletes Are Following to Avoid Illness: Staying healthy is key to the quest for glory in Milano Cortina, so athletes are deploying the latest science.

A look at the latest data on avoiding exposure, boosting immunity, and fighting infections after they start. TLDR: if you really want to stay healthy for an important event, your best bet is probably masking up.

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Alex Hutchinson

To support my work, check out my latest book, The Explorer’s Gene: “science writing at its very best, with something fascinating on every page,” according to David Epstein.