MICHEL MARTIN, HOST:
Hey, A.
A MARTÍNEZ, HOST:
Yes.
MARTIN: Did you get a workout in this weekend? How'd it go?
MARTÍNEZ: I got two. One was an easy one, and the second one was I put myself through the ringer.
MARTIN: (Laughter) Excruciating. OK.
MARTÍNEZ: Yes. Yeah.
MARTIN: Well, in the world of professional sports and fitness, people talk about training zones as sort of spectrum of intensity from light exercise to really huffing and puffing - sounds like that was you. For more casual athletes, one zone in particular is getting a lot of attention - Zone 2. NPR's Will Stone has this report.
WILL STONE, BYLINE: Ask Carl Foster about the merits of Zone 2 training, and first, you'll get a question.
CARL FOSTER: What Zone 2 are you talking about?
STONE: The answer can depend on the sport, the country or even the kind of researcher you are. For instance, Foster is an exercise physiologist.
FOSTER: And we tend to think in terms of only three zones. And Zone 2 is sort of the middle zone, and it's athletic.
STONE: Tough. You're not entirely at your max, though. And Foster says there are thresholds you can clearly measure with blood tests and breathing patterns. But if you run into Zone 2 chatter these days, chances are, this is not the intensity people are talking about. Instead, they're describing something more chill - you can do for longer periods of time.
FOSTER: And Zone 2 is you can do a lot of training, and you can get a lot of benefit with very minimal pain. And so that's attractive.
STONE: Here, Zone 2 sits on the lower end of a five- or six-zone scale, maybe even more. Stephen Seiler is an exercise researcher at the University of Agder in Norway. He says professional cycling has fueled the current Zone 2 phenomenon. Because athletes are doing long training rides, they need to fine-tune their low-intensity work. But translating all this to the general public and different endurance sports can get tricky.
STEPHEN SEILER: There's not a magic zone. That's what the research tells us.
STONE: Unlike elite athletes, the average runner doesn't necessarily have this wide range of lower-intensity effort.
SEILER: It can be very narrow. I know that by experience coming back into running and feeling like, oh, my goodness, I can barely run before I'm starting to feel like this is no fun.
STONE: Seiler has popularized polarized training. The idea here is that most of your endurance training should be in this easier, more sustainable realm, and then a smaller percentage at higher intensity. This is based on research of top athletes. But Seiler says the principle is helpful for all of us because...
SEILER: The most common mistake is everybody ends up - their workouts all kind of regress towards the middle. And there's nothing wrong with that kind of workout, but if you do it every day, if you do it every time you train, then you stagnate pretty quickly.
STONE: So to avoid slipping into that pattern, he says there are some simple hacks for finding this Zone 2 space. You can basically have a conversation. Your heart rate levels out after 10 to 15 minutes, and you can eat pretty quickly after the workout.
SEILER: Then, yeah, other days you're going to train harder, but you're putting together - you're composing an orchestra of training that's not all one note.
STONE: Now, some of the recent enthusiasm around Zone 2 is based on claims that it has special metabolic benefits, including for burning fat that make it better. Brendon Gurd at Queen's University in Canada says the data don't really support that.
BRENDON GURD: If you just want to get a little bit fitter and be active and be healthier, Zone 2 is great, but if you want to sort of maximize your four hours a week, the best four hours is probably going to be high intensity.
STONE: Billy Sperlich at the University of Wurzburg in Germany agrees. If you're just looking at return on investment for cardiovascular benefits, burning energy, high intensity wins out. But you can't do that all the time. And he also sees the current interest in the Zone 2 concept as part of a broader back-and-forth in the fitness world.
BILLY SPERLICH: We had a very, very strong, I would say, hype on high-intensity exercise, and all of a sudden, whoop, everything went back to low-intensity exercise. The answers were endurance athletes. It's a mix, basically.
STONE: And while there are different schools of thought about the exact mix, proponents of Zone 2 point to another upside - when a workout isn't too brutal, you're more likely to do it again.
Will Stone. NPR News.
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