New Study: Light Weights Good for Building Muscle, Too?

Conventional wisdom holds that heavy weights and 7 - 12 reps is best for muscle growth - but a new study suggests that light weights and high reps works, too.

So you’re trying to build muscle? Great.

If you ask any personal trainer about the number of repetitions of each exercise that you should perform, the trainer would most likely advise you to target somewhere between 7 and 12 reps until you experience muscle fatigue. In other words, you’ll be using a heavy weight for a fairly low number of repetitions.

A new study suggests that there’s another way to build muscle – and it flies in the face of conventional wisdom. According to the study, performing light weights for a high number of repetitions until fatigue also results in similar muscle growth.

For the study, researchers calculated the maximum load for each individual and then broke the participants into one of three groups as follows:

  1. Exercisers perform one set at 80% of the maximum load until fatigue, or
  2. Exercisers perform three sets at 80% of the maximum until fatigue, or
  3. Exercisers perform three sets at 30% of the maximum until fatigue.

Performing sets at 80% of the maximum load usually results in rep ranges of 7 – 12. Training at 30% of the maximum load, on the other, results in much higher rep ranges of 25 – 30.

According to their data, participants in groups 2 and 3 gained the same amount of muscle mass. In other words, training with heavy weights and low reps resulted in the same muscle growth as light weights and high reps. Notably, participants in group 2 – whose training most closely mimics conventional muscle building strategies – resulted in larger strength gains than group 3. Participants in group 1 experienced approximately half the muscle growth as groups 2 and 3.

Because group 2 exercisers experience increased gains in strength, rep ranges of 7 – 12 are still ideal. And, fewer reps means less time at the gym – so lower rep ranges with heavy weights make for a more efficient workout.

But because lower repetition ranges require heavy amounts of resistance, they can be intimidating for beginners. Moreover, heavy amounts of resistance can prevent people with joint issues – and, in particular, older populations – from utilizing the heavy resistance/low rep training strategy.

The implication of this study is obvious: Don’t let current strength training guidelines deter you from lifting weights and thus receiving the associated health benefits. If the heavy levels of resistance associated with lower rep ranges is a limiting factor for you, this new research suggests that light loads can also yield great results.

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  1. It makes me a bit iffy that they used the opposite legs of a person for control and condition. But interesting find nonetheless.

  2. charley says:

    Overload leads to adaptation. First principle. So however you achieve overload, by more weight or more reps, your body will get stronger to adapt. Once it does, you need to again overload, i.e. more weight or more reps.

    Super slow sets at the lower weight is another neat way of increasing resistance, in this case gravity.

  3. i havent lifted heavy weights in 6 years.. 6 yrs ago i could max bench 235 lbs.. 20 lbs + my “then” body weight.. 3 sets.. to failure maybe 6 reps.. 8 on a good day.. today i max out at 115.. 3 sets.. to failure 12 reps.. i am more ripped and leaner than i was six years ago.. stronger? idk.. i am 47 and heavy weights just make my joints ache.. snap.. crackle, and pop… i stopped trying to get bigger when i realized that im not getting any younger.. the huge older dudes at the gym look so bloated & “boxy”.. ugh.. i see a lot of younger lean guys buying into the myth that they have to get swoll to be happy.. or sexy.. or noticed or w/e.. stay lean.. its way attractive and healthier in the long run..

  4. Ive been using heavier and heavier weights at my local gym and have noticed alot of improvement but my partner at home has been using the same light weights does a crazy number of reps and he is just as big as I am. Im not surprised at these findings.

    • Interesting comment you made Paul, esp. in contrast to you and your partner being of simialr build, but different training. Do you have any problems with your joints yet? I’ve had conversatons with guys that were lifting lighter for they were having joint pain with heavier weights. Ive noticed with myself when I do a high intensity lower weight workout like the “Crazy 8’s” (50 to 60% of normal trainging weight, doing 8 sets, with 8 reps, with 8 seconds rest between sets at a medium pace) wears me out, and gives me a better pump, and a longer lasting pump then heavier weights do. I am sure genes play a role, as does diet, but I think there is somethign to this. Be interesting to see your partners type of workout, if he ever cares to share. Maybe the lighter weight workout will debunk the heavy weight workouts for size, as Bill Phillips did for showing what kind of great results you canget in a gym just a few hours a week, as opposed to a few hours a day like a lot of body builders do.

  5. christopher says:

    im not suprised by these findings at all.lighter weights and more reps is the way to go.that should get the results im after.consistency in the long run-is what im after.

  6. I’m pleased to see this new information – it verifies what I’ve been doing for the last 6 months.

    Previously, I’d been trying to build muscle the old-fashioned high weights and 10-12 reps way.

    Then I thought about how many tradesmen (of which I’m not) build muscle – they don’t lift heavy weights but are constantly moving smaller weights around (e.g. bricks, pipes etc).

    So, I reduced my without load to about 60% of my limit and do reps of 40. Results ? – the best I’ve ever had, tone and muscle and now joint ache either As I am now 54, I don’t want that…

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