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The Latest Research on Protein and Muscle-Building 

Insights from this year’s ACSM conference on how to lift, what to eat, and how that affects endurance athletes

Pounding protein shakes didn’t make study volunteers better endurance athletes. (Javier Díez/Stocksy)
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One of the most grueling endurance events I’ve ever participated in is the American College of Sports Medicine’s annual meeting. From dawn to dusk every day for nearly a week, scientists present the latest results from their labs. At any given moment, there are at least three presentations that you wish you could see happening simultaneously. It usually takes place in conference centers so vast and cavernous that flitting from one talk to another involves logging serious mileage.

The payoff is a glimpse of what topics are currently roiling the waters of sports science. In some cases, the results being presented are still a year or two away from appearing in a peer-reviewed journal, so interpreting them requires caution. With that caveat, I’m going to share over the coming days a few themes that emerged at this year’s conference, which took place in Orlando from May 28 to June 1.

For starters, here are three presentations on protein and muscle-building that grabbed my attention, with insights on how to lift, what to eat, and what that means for endurance athletes.

How Much Lifting Is Too Much?

The debate about how many sets of each exercise you should do while strength training is a very old one, and I’m afraid I’m not going to offer any final answers. There seem to be many different approaches that yield similar results, rather than one “right” way of doing it. But one of the ACSM presentations, from a group led by Matheus Barbalho of Federal University of Goiás in Brazil, offers some big-picture insights.

The researchers put 37 volunteers through a 24-week training program, doing four key exercises: bench press, lat pull down, 45-degree leg press, and stiff-legged deadlift. The volunteers were divided into four groups, doing a total of either 5, 10, 15, or 20 sets per muscle group per week. Their strength for each exercise was assessed with a 10-repetition-maximum test after 12 and 24 weeks, and their muscle size was measured with ultrasound.

All four groups gained strength and muscle size. But the 5- and 10-set groups got stronger than the 15- and 20-set groups on all four tests, after both 12 and 24 weeks. For muscle size, all four groups were equivalent. So based on these results, 5 to 10 sets for each muscle group per week seems to be not only sufficient, but optimal to build muscle strength and size.

This actually backs up some of the previous research on the topic, which found that even just one set of 8 to 12 reps per exercise, three times a week, was enough to more or less maximize strength gains (though that study did find increases in muscle size with more sets). There’s plenty of scope for debating the details here, but the takeaway for me is that if you’re not a bodybuilder—i.e. if you’d like to get stronger in support of other activities or for health reasons—then given the tradeoffs of time and energy, it’s probably better to focus on a few high-quality sets per muscle per week rather than accumulating huge numbers of sets.

Can You Get Ripped on Plants?

This is a topic that inspires strong feelings, to put it mildly. There have long been studies showing that some protein sources are better than others, at least in isolation. Protein sources that contain high levels of an amino acid called leucine seem to be particularly effective at stimulating the synthesis of new muscle, which explains why dairy protein outperforms soy protein in head-to-head, gram-for-gram matchups.

But no one lives on soy (or dairy) alone. Do those subtle differences matter if you’re eating a broad diet with many different sources of protein? Another Brazilian study, this one from a group led by Victoria Hevia-Larraín of the University of São Paulo, explored this question by enrolling 19 vegan and 19 omnivorous young men in a 12-week, twice-a-week strength training program. Both groups were given protein supplements (either soy or dairy) to equalize their protein intake at a goal level of 1.6 grams per kilogram of bodyweight per day, which is twice the recommended minimum for sedentary adults but a relatively typical level for athletes.

The results in brief: no differences between the two groups, which each increased muscle mass by about 6 percent and strength by 38 to 49 percent. So the subtle differences in protein “quality” (e.g. leucine content) seemed to matter less than simply getting a sufficient amount of protein. You could argue, of course, that getting enough protein is trickier if you’re avoiding meat and dairy. But that’s really a different question. It’s certainly possible to eat like crap no matter what dietary tribe you belong to; what this data suggests is that it’s possible to get the protein you need, even as an athlete, on a plant-based diet.

Do Endurance Athletes Need Protein Shakes?

A few years ago, researchers using a new protein-tracking technique published some data suggesting that endurance athletes have heightened protein requirements. In one sense, this was a bit surprising—we usually think of protein shakes as the domain of muscle-heads. But in other ways, it shouldn’t be a surprise. Even though carbs and fat supply most of the energy for exercise, prolonged exertion can tap into your protein stores for up to 10 percent of the needed energy. And protein provides the amino acid building blocks for repairing and rebuilding muscle damage incurred in training. That previous data suggested endurance athletes should aim for closer to 1.8 g/kg/day rather than the 1.2 to 1.4 g/kg/day often recommended for them.

At the ACSM conference, a team at the University of Applied Sciences in Nijmegen, Netherlands led by Kristin Jonvik put this idea to the test. They enrolled 60 volunteers in a 12-week, three-times-a-week endurance training program. After every workout and every night before bed, the volunteers took a shake that contained either 29 grams of protein or a placebo drink with no protein but the same number of calories from carbohydrate. This had the effect of boosting the overall protein intake of the protein group to 1.6 g/kg/day, while the placebo group stayed at 1.2 g/kg/day.

To figure out whether the extra protein made a difference, they did before-and-after VO2max tests, 10K cycling time trials, a muscular endurance test that involved 30 all-out contractions, and measured body composition. The volunteers got fitter in pretty much every way, but there were no differences between the two groups: pounding protein shakes didn’t make them better endurance athletes.

This doesn’t quite close the book on protein for endurance athletes. It may be that recreationally active volunteers training three times a week don’t have elevated protein needs, whereas serious endurance athletes training seven or 10 or 14 times a week do. On the other hand, athletes who are training really hard tend to get a lot more protein anyway simply because they’re eating way more overall. There’s a theoretical reason to think endurance athletes need more protein than previously thought, but the first practical test of this idea doesn’t show any real-life benefit.


My new book, Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance, with a foreword by Malcolm Gladwell, is now available. For more, join me on Twitter and Facebook, and sign up for the Sweat Science email newsletter.

Filed To: AthletesDietScienceEndurance Training
Lead Photo: Javier Díez/Stocksy
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