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Another interesting strength-training study just popped up, this one published in PLoS One. The claim in the press release is quite eye-catching: “Building muscle doesn’t require lifting heavy weights.” This is a leap of logic that isn’t quite supported by the paper itself, whose claims centre on “stimulating muscle protein synthesis ” and “inducing acute muscle anabolism” rather than actually demonstrating big muscles. Still, it’s a very surprising study, from a well-respected group (Stuart Phillips at McMaster University).
The study compared three different weights routines:
(1) lift at 90% of one-rep max until failure;
(2) lift at 30% of one-rep max until you’ve lifted as much as you did in the first routine;
(3) lift at 30% of one-rep max until failure.
Deeply entrenched dogma tells us that the best way to build big muscles is to lift heavy weights — option (1) in the workout routine. But the researchers injected tracers and took muscle biopsies four and 24 hours after each workout to find out what was happening on a cellular level. They found that the first and third routines were the same on most measures of protein synthesis, and the third routine was even better on some measures. Those new proteins being synthesized are what accumulate, over time, to produce bigger muscles. So as long as you’re lifting until can’t lift anymore, you’ll do as well or better with light weights as you would with heavy weights.
This is some serious heresy being proposed, and it’s important to note that they didn’t actually observe bigger muscles, just cellular markers. The researchers themselves note that “a training study in which these distinctly different exercise loads are utilized is clearly warranted to confirm our speculation.”
Whatever the training study eventually shows, it’s hard to imagine that this will affect how serious muscle-builders train. However, the researchers believe it could have important implications for “people with compromised skeletal muscle mass, such as the elderly, patients with cancer, or those who are recovering from trauma, surgery or even stroke,” since it minimizes the risk of orthopedic and soft-tissue injury. I’d generalize that even further — there are many, many people who are intimidated by the prospect of trying to lift heavy weights, but might be willing to lift a lighter weight 20 or 30 times until they can’t lift it anymore. Of course, that’s the crux: the method only works if you reach failure, so it’s still going to hurt. You’re just less likely to cause a scene at the gym by dropping the weight on your foot.