Building muscle with light weights


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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.

8 Replies to “Building muscle with light weights”

  1. It doesn’t look like they matched the subjects for training volume – the 30FAIL group did 50% more work than the 90FAIL group (1073kg vs 710kg), which goes some way to explaining the increased protein synthesis in the 30FAIL group.

  2. True… and that’s sort of the point, I think. In the 90FAIL session, the subjects lifted to failure, so they couldn’t lift anymore even if they wanted to. By lifting lighter weights, they were able to do more volume before they reached failure, and thus got a greater training stimulus.

    They also did a session (30WM) with the explicit purpose of lifting light weights but matching the volume of the heavy-weight session, which — as we’d expect — wasn’t as effective at stimulating protein synthesis.

    Of course, it’s still an open question as to whether the protein synthesis results translate into greater strength gains and/or hypertrophy in real training studies. The “real world” generally ends up being a bit more complicated than these reductionist studies!

  3. Another interesting comment from Christian Finn, which I accidentally deleted while purging spam (sorry about that, Christian!):

    The simple way to match training volume would have been for the 90FAIL group to do more sets (both the 30FAIL and 90FAIL group did 4 sets).

    Powerlifters and strength athletes using low reps (doubles or triples) will do more sets per exercise in order to get the volume in.

    As the number of repetitions goes up, the number of sets will go down. For example:

    3 sets of 8 reps = 24 reps
    4 sets of 6 reps = 24 reps
    5 sets of 5 reps = 25 reps
    6 sets of 4 reps = 24 reps
    8 sets of 3 reps = 24 reps

    So while the sets and reps change, the total number of repetitions stays pretty much the same.

    The way this affects training volume is shown near the bottom of this article:

    The Three Best Ways To Gain Muscle

    Suggesting that “building muscle doesn’t require lifting heavy weights” would be a valid conclusion to draw only if training volume was identical in both groups. Which it wasn’t.

  4. Even if the result of the experiment are valid – there is still a distinction between body building and strength building.

    “Deeply entrenched dogma tells us that the best way to build big muscles is to lift heavy weights”

    I don’t think the dogma says that at all – I think it is generally established that body builders (people primarily concerned with increasing muscle mass) do exercises with lower weight but more reps.

  5. Thanks for the comment, David. I agree that bodybuilders aren’t exclusively lifting 90% of 1RM, but I hadn’t heard that they were using weights as low as 30%. For example, the ACSM position stand on resistance training says “RT programs targeting muscle hypertrophy have used moderate to very high loading, relatively high volume, and short rest intervals.” Certainly, this could be yet another case of the athletes being ahead of the scientists. But I think it’s fair to say that “conventional wisdom” still favours much heavier weights than 30% of 1RM for building muscle mass.

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