Let’s say you want to get fit, but don't know what kind of workouts to prioritize. A new study in this month’s Journal of Science and Medicine in Sport will tell you to lift weights instead of hopping on your bike. Burning calories via strength training, it found, will ultimately help you shed more fat than burning the same amount of calories doing moderate cardio like cycling.
That’s the headline readymade for media buzz, anyway. But before you swap out your trainer for barbells, a few words of caution.
First of all, the study was funded by Les Mills International, the New Zealand brand behind the group barbell class BODYPUMP. So from the outset, it had a vested interest in promoting weight lifting. Researchers examined 12 recreationally active women during and after a resistance training workout—a BODYPUMP class, of course—and a steady, moderate-intensity session on a stationary bike.
Both workouts burned around 335 calories and boosted levels of human growth hormone (HGH), which promotes fat burning and muscle development. But the women’s HGH levels were 56 percent greater after the resistance workouts (in this case, light to moderate weights with high repetitions) compared to the steady-state cardio bouts.
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“The more muscle you can build, the more calories your body will burn long-term,“ lead researcher Nigel Harris, of the Auckland University of Technology, said in a press release. ”Combine that with increased fat loss, and the result leads to rapid changes in body composition.”
While the result isn’t all that surprising, it provides a good opportunity to drive home a few truths we already know. For one, people need to stop obsessing over calories, whether it’s what you’re taking in or what you’re burning off. Human beings are not Bunsen burners. And as athletes, we’re no dummies: We know that calories from an avocado are processed differently than those from a pack of mini powdered doughnuts.
It’s also no shocker that strength training affects your body differently than cardio regardless of the ultimate calories burned doing either. Though you may see headlines around this study claiming strength training is superior to cardio, the research reinforces the long-recommended advice that both cardio and strength training are essential for healthy, functional athletes. Studies dating back to the 1980s have documented increases in HGH, even among seniors, in response to resistance training. Making and maintaining lean muscle is essential for everybody.
In addition to the narrowness of the study—only 12 women!—it also overlooks the fact that many dedicated athletes like cyclists don’t exercise with the mission of burning a set number of calories. We ride because we love it, so we may (and often do) go longer than 45-60 minutes, which incidentally also boosts HGH. A 2014 study published in Medicine & Science in Sports & Exercise found that doing two hours of cardio boosted HGH secretion more than doing 1-2 hours of strength training.
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We also tend to go harder. Whether we’re doing specific high-intensity interval workouts, competing in an event, sprinting for a town line, riding a hilly route, or just duking it out with friends on a group ride, we rarely ride at a steady, 68-percent-max-heart-rate intensity. And when we push the pace, our HGH levels soar. One study on sprint intervals found that just one 30-second sprint interval increased HGH by more than 430 percent. In fact, that burning you feel in your legs while hammering down the road is a good sign you’re pumping out HGH.
Finally, the Les Mills study also measured blood lactate because prolonged exercise (more than 10 minutes) above lactate threshold is known to stimulate secretion of HGH. Not surprisingly, blood lactate was much higher (81 percent) during BODYPUMP than during moderate steady cycling, in which lactate is cleared as it’s being produced. But it’s also very easy to hit levels above lactate threshold on a non-steady, spirited ride.
The bottom line here is: enjoy your ride, lift some weights, and don’t get caught up in the calorie-counting hype.
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