Dearest Fellow Athletes,
In the past few days, you may have come across the wildly popular New York Times article titled, “1 Minute of All-Out Exercise May Have Benefits of 45 Minutes of Moderate Exertion.” Such a promise would understandably get busy go-getters like you all up in a tizzy, dreaming about Insta-fitness and newfound time. That is why I must say, in the kindest way possible, this article is not for you, nor is the study it's based on.
“Nearly all of the high intensity studies are done with recreationally active or sedentary subjects,” writes one of the study’s authors, Mark Tarnopolsky, in an email to Outside. Tarnopolsky is a medical professor at Canada’s McMaster University and a top researcher in exercise adaptation.
In this particular “1 Minute” study, published this week in open-access journal PLOS ONE, he and his colleagues made sedentary men in their 20s and 30s work out three times a week for 12 weeks. One group did 3x20 all-out sprints on an exercise bike with easy cycling in between, for a total workout time of 10 minutes. The other group cycled continuously at about 70 percent of their max heart rates for 45 minutes. (In general, exercising at 50 to 70 percent of one’s max heart rate is considered an easy workout.) In the end, both groups’ health and fitness improved similarly, with everyone improving their oxygen intake, blood sugar control, and muscle function.
Of course, Tarnopolsky writes, the stress of the intervals is similar or more potent compared to moderate intensity exercise. So interval training looks great in the short term. “BUT”—his caps, not mine—“extrapolating to the long term (years to decades) I seriously doubt that ANYONE IN THE WORLD could keep up only this type of training without injury or getting bored/flat/stale.” Yes your endurance will improve a ton with a minute of intervals if you had no endurance to start with, but it’ll flat-line pretty quickly if you don’t keep upping the ante. And you, athletes who are prepping for 5Ks and 10Ks and ultramarathons and bike races and such, have already upped the ante.
That’s not to say intervals shouldn’t play a role in your training. They should. “I think that every runner in the world for the past 50 years has known that doing some intervals in the 6 to 8 weeks before the racing season helps,” Tarnopolsky writes. “The added stress likely alters signaling molecules that respond to stress.” If you always go the same pace, those signals don’t get turned on, and you don’t get much faster. “Ramping it up with intervals stresses the system and further ‘tops up’ an already well tuned system,” he writes.
But sprint interval or high-intensity interval training isn’t something you should do year-round. Try to keep that up and you’ll get “great results for a few months to perhaps years and then blammo,” he writes—injury, staleness, overtraining syndrome.
It’s also important to note that when we’re talking about sprint intervals in your training, they’re not necessarily anything like the intervals examined in research like this "1 Minute" study. The “high intensity intervals” used in epidemiology studies—the kind that look into the control of diseases like diabetes in the general population—are often nowhere near as intense as the intervals athletes do.
“The epidemiology is essentially doing something near or at the talking threshold as ‘high intensity,’” Tarnopolsky writes. That level of exertion may feel like an all-out sprint for someone who never exercises. But athletes looking for a physiological boost from intervals typically do them closer to 90 percent of their max heart rate. If you can talk, you’re not going hard enough.
In conclusion, Tarnopolsky writes, it’s ludicrous for anyone to think they can do well at something like a half marathon with just a few minutes of interval training. You have to “log the miles to build tenacity, ligament and muscle toughness under long term fatigue, cardiac adaptations,” better fat utilization, lactate tolerance, and general tolerance to race pace, he writes. Not to mention, the overall calorie burn with a one-minute workout will be far less than with a longer effort. That’s something to consider if weight loss or maintenance are part of your training goals.
So if you’re pressed for time, do a quick workout with hard intervals; it’s certainly better than nothing. Just don’t believe the promise—that was never really made—that a one-minute workout will launch you toward your endurance goals.
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