When I started running in the mid-1980s, only hardcore endorphin junkies knew what VO2max was. We read the books that cited the studies showing that peak oxygen consumption during intense exercise (i.e., VO2max) predicts performance better than any other indicator. In 1987, for example, researchers at NASA’s Lyndon B. Johnson Space Center tested 50 male runners of varying ages and abilities and found a correlation coefficient of 0.63 between VO2max and running performance, meaning peak oxygen consumption alone accounted for more than 60 percent of individual differences in marathon times.
Today, thanks to podcast influencers like Dr. Peter Attia, author of Outlive, and the Zone 2 training trend, even the most casual athlete is aware that adding horsepower to the aerobic engine supercharges performance like nothing else. But the real mainstreaming of VO2max happened when health-conscious senior citizens learned that aerobic capacity is also among the strongest predictors of longevity. An ambitious 10-year study published in the European Journal of Preventive Cardiology found that VO2max was a better predictor of mortality than body mass index or frailty in a population of 552 elderly adults. Simply put, the more horsepower an older person has in their aerobic engine, the less likely it is that person will die anytime soon.
We tend to think of fitness and health as two separate things—related but distinct. But the fact that VO2max is correlated with both endurance performance and longevity suggests otherwise. And the overlap between fitness and health goes well beyond aerobic capacity. The table that follows summarizes the effects of endurance training on a variety of bodily organs and systems and how these effects benefit both health and fitness.
As you can see, pretty much everything endurance training does to the body elevates health and fitness equally, which tells us that health and fitness aren’t merely related but the same. People often say that health is the foundation of fitness, implying that fitness is something we layer on top of health, adjacent but separate, when in reality fitness is just more health. One scoop of endurance training, so to speak, gives you health. Two scoops give you fitness.
Not every athlete understands this. Believing they can pursue fitness independently of health, many bargain their health away in exchange for a false promise of greater fitness. Common pitfalls are restrictive eating, overtraining, and obsession—three ways of chasing fitness that often pay short-term dividends but always cause long-term erosion of health, and when health erodes, so does fitness.
My three rules for avoiding these pitfalls are:
- Train for tomorrow.
- Eat like your great-great-grandparents.
- Be balanced.
Let’s explore the first of these rules here.
Train for Tomorrow, Not Today
It’s natural to associate hard work with improvement as an endurance athlete. But although hard work is the most obvious contributor to fitness, there are many more pieces to the puzzle, and athletes who approach their training with a “more is better” mindset invariably sabotage their fitness by impairing their health.
Ryan Hall can tell you a thing or two about that. When he left his longtime coach Terrence Mahon in 2010 to become self-coached, Hall was unquestionably the greatest male distance runner in the United States, having finished third in the Boston Marathon the prior year and having set the American record in the half-marathon in 2007. But in 2012 he decided it would be a good idea to attempt to break the marathon world record at the Olympic Games in London, and he prepared for it by completing long solo training runs at world-record pace. The result was a hamstring injury that forced him to abandon the race at 11 miles, and he was never the same. After withdrawing from the 2013 Boston Marathon and the 2014 New York City Marathon and dropping out of the 2015 Los Angeles Marathon, Hall retired from competitive running in 2016, citing chronic fatigue and low testosterone, both common signs of overtraining. He was 33 years old.
“I see within myself [a] desire for quick results,” Hall wrote on his blog near the end. “I’m tired of making that mistake.” Sara Hall, meanwhile, avoided duplicating her husband’s mistake, training for tomorrow instead of today, and was rewarded with impressive longevity, setting her own American record in the half-marathon at age 39.
A good description of “training for tomorrow” comes from another American record holder, Emily Sisson, who clocked 2:18:29 at the Chicago Marathon in 2022 and is coached by Ray Tracy, a venerable developer of collegiate and elite talents who believes that without health there can be no fitness. In a 2019 interview for Athletics Illustrated, Sisson said of her coach, “Ray is very conservative with everything and really stresses staying healthy so you can continue training without taking weeks or months off. So he’s big on staying on top of the little things, taking a day off if you’re not feeling well or have a little niggle in your foot or leg. He knows that in the long run the workouts aren’t the be all and end all; it’s more important to get out and run every day, consistently, for a long time. That consistency is what really brings improvement.”
Be like Sara Hall or Emily Sisson, not Ryan Hall, and train for tomorrow, not today.
Health and More Health
The first 200 men to break 4 minutes in the mile have lived 4.7 years beyond their predicted life expectancy (and likely enjoyed a high VO2max). That’s according to a 2024 study published in the British Journal of Sports Medicine, and it aligns with previous research, including a 2022 study from the same journal, which reported that male and female Olympic athletes from the United States outlived their peers in the general population by 5.1 years.
People don’t go to the Olympics to live longer, however. They go to the Olympics in search of the absolute limit of their athletic ability. But because endurance fitness and health are two facets of a single phenomenon, these athletes get a two-for-one—except when, hungry for quick results, they take shortcuts, like too much high-intensity training, that may sometimes yield extra VO2max fitness in the short term but invariably sabotage fitness by eroding health in the long term.
Don’t be this athlete. Sure, you might still live an extra five years if you adopt a restrictive diet or train like Ryan Hall or allow your athlete identity to define you, but you will not master your sport. You can’t win a race you don’t finish, and like it or not, you cannot be fitter than you are healthy. Wherever you get your instruction, get it from folks who know this.
Chasing Mastery From Principle to Practice
Endurance fitness is an extension of general health, but it’s unwise for an athlete to chase fitness at the expense of health. If you hope to reach your full potential, take a minute to consider how much fitness and performance matter to you relative to health. We all care deeply about our health, of course, but some of us care even more about our fitness and performance, and that’s fine. It’s a personal choice. But regardless of priorities, every athlete must put health before fitness in practice to achieve their best, and all benefit from having a clear understanding of their priorities. What are yours?
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