A few years ago, a friend proudly showed me his new sports watch. “Look, it shows my VO₂max.” There was a number on the display. I asked him whether it was good. He said: “No idea. But it’s there.” That, in one sentence, is most people’s relationship with their endurance fitness: they sense there’s an important number, but nobody has explained what it means or what to do with it.
Let’s catch up on that here. Calmly, honestly, without the usual hype. Because right now there’s a real endurance fever online: “Zone 2”, “VO₂max”, “longevity”. Much of it is true. Some of it is exaggerated. And a few things are told wrongly so often that they deserve a chapter of their own.
Why VO₂max says more about you than your scales
VO₂max is the maximum amount of oxygen your body can use per minute under exertion. Think of it as the size of your aerobic engine. And this engine is surprisingly telling: in a large analysis of more than 120,000 people, higher fitness was associated with a much lower risk of death, with no visible upper limit (Mandsager et al., JAMA Network Open, 2018). An older meta-analysis puts the relationship like this: for each additional level of fitness, measured as one so-called MET, the risk of death fell by about 13 percent (Kodama et al., JAMA, 2009).
The honest context matters: these are observational data. They show a strong association, not watertight proof of cause and effect. Part of the effect surely reflects that healthier people are fitter, not just the other way round. But fitness is one of the few factors you can actively change. And that’s exactly what makes it so valuable. If you start from the bottom, you gain the most: the curve is steepest at the start.
The Zone 2 myth, kindly taken apart
Now for the elephant in the room. “Zone 2”, easy training where you can still talk in full sentences, is currently being sold as the secret to a long life. The sober truth: Zone 2 is good, but it isn’t magic.
Easy endurance training builds your aerobic foundation, is kind to your joints and can be sustained at high volume. But the claim that it’s the only, uniquely effective intensity doesn’t hold up to science. If you keep training effort constant, more intense training delivers at least as much for VO₂max and mitochondrial adaptation, often in less time (MacInnis & Gibala, Journal of Physiology, 2017).
The reason for the hype is, honestly, human: Zone 2 feels good. It doesn’t hurt, you can listen to a podcast, and afterwards you feel proud. But “feels good” and “works best” are two different things. The mistake isn’t doing Zone 2. The mistake is believing that only Zone 2 counts.
Three feelings instead of five formulas
Many people already fail at the theory: five zones, lactate thresholds, “220 minus age”. You can simplify this enormously. There are basically three feelings. Easy: you could make a phone call at the same time. Medium: talking gets hard, sentences get short. Hard: talking is beside the point. The so-called talk test, how well you can still speak under exertion, is often more accurate than any formula for your everyday training. And it costs nothing.
The most common mistake hides right in the middle. Most recreational athletes get stuck in the middle zone: permanently medium-hard, too strenuous to recover, too soft for real progress. The solution is polarised training: about 80 percent easy, 20 percent really demanding, almost nothing in between. Systematic reviews tend to show better VO₂max gains for this distribution than for pure threshold training. With three sessions a week, that simply means: two easy, one intense.
Intervals aren’t elite sport
When they hear the word “intervals”, many people think of collapsing. Yet an interval is just a short phase in which talking is hard, followed by recovery. To start, this is enough: one minute brisk, two minutes easy, six to eight times, with a good warm-up and cool-down. Over the weeks you extend the hard phases. It’s about controlled effort, not self-destruction. An honest note, not small print: if you have cardiovascular conditions or haven’t done anything for a long time, get intense exercise cleared by a doctor first.
“Cardio kills muscle” and other gym legends
That leaves the toughest myth: that endurance ruins muscle growth. The largest review on this, with more than 40 studies, finds no meaningful disadvantage of endurance training for strength and muscle growth (Schumann et al., Sports Medicine, 2022). Only maximal explosive strength can suffer, mainly when you cram both into the same exhausting session. For health and looks, cardio isn’t the enemy of your muscles but their colleague. Strength and endurance are two pillars of the same healthy body.
The honest plan to finish
Let’s get concrete. A sensible week for most people with little time: three endurance sessions, two easy and one intense, plus strength training twice. Don’t measure your progress on the scales but on the stairs: the same staircase, every few weeks, and notice whether you’re breathing more calmly at the top. Because your scales measure mass, not health, and in large studies fitness often predicts life expectancy better than body weight.
And if all that sounds like too much: start deliberately too small. A 15-minute walk after lunch, every day, isn’t a compromise, it’s the beginning. The smallest dose that actually happens beats the perfect plan that fails. By the way, my friend with the sports watch now knows what his number means. More importantly: it has gone up, because he stopped staring at it and started taking the stairs.
Medical note: this article doesn’t replace medical advice. If you have pre-existing conditions, or before intense exercise, please get checked by a doctor. alethics does not make diagnoses.
