Machines and free weights are equally effective, study shows

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Machines versus free weights. Which one is better to build muscle, to build strength, and which one is easier on your joints? We now have relatively conclusive scientific evidence to these questions.


0:00 Intro

0:57 2023 study

1:28 2021 meta

3:12 2008 Spennewyn et al. study

4:06 Conclusion


 Machines versus free weights. Which one is better to build muscle, to build strength, and which one is easier on your joints? We now have relatively conclusive scientific evidence to these questions. On the one hand, there is the perspective from bodybuilding circles that says machines are better for muscle growth because it takes the stabilizers out of the movement and therefore you can really hammer the targets musculature. On the other hand, if you go to the more functional training strength training type crowd, you will find a lot of people that say, well, machines are inferior for strength development, it’s probably worse for your joints and maybe also worse for muscle growth. However, that is, I think, largely an ideological stance rather than really a fact-based objective view of the world. Heavy barbell back squats have become almost like a rite of passage, like to be a serious strength trainee, you have to do free-weight training. You have to do heavy squats.

And that’s not necessarily true. A new study compared a program that was fully identical, except that one group performed it with a barbell and the other group performed the exercises using a similar movement trajectory with machines. They found that muscle growth was similar for the quads, the pecs and the abs, all tested muscles. Strength gains were modality specific, meaning they were exercise specific. So the machine group gained more strength on their machines and the barbell group gained more strength on their barbell lifts. these findings align well with a 2021 meta analysis of the literature, which found that if we look at all studies together, indeed, machines and free weights are equally effective for both muscle growth and exercise specific strength development. And it makes perfect sense if we think of muscle as just a piece of meat, essentially. That’s one of my favorite quotes from Norwegian Strength Coach Borge Fagerli. He likes to say that muscle is just a dumb piece of meat. It responds to mechanical tension and it adapts accordingly to get bigger and stronger. It doesn’t matter whether that tension is imposed from a kettlebell, a machine, a barbell, an isolation exercise, a compound exercise.

That stuff all doesn’t really matter. The muscle just responds to the tension that is imposed on it. Now, if we look at strength transfer to other exercises, then we do see a bit of a trend towards machines being inferior. If we look at the 2021 meta analysis, most of the effect sizes did trend in the direction that the strength transfer of barbell exercises or free weights exercises in general transfers a little bit better to machines than the other way around. We also have some research that indicates that free-weight type exercises transfer a little bit better to sport specific movements, although in most studies the difference is not statistically significant and is generally wildly overblown if you listen to the functional movements crowd. Because in the end, most of the functional development that you get is from just muscle growth, first and foremost, and then muscles learning to coordinate during basic movement patterns. Regarding joint pain in the new study, they found that joint discomfort was similar or actually it improved similarly in both the machine and the barbell group.

This finding contrasts with a previous study by Spennewyn from 2008, which compares two types of machines. But one machine had a very high freedom of movement, so it was almost like a free weight. And the other group had a very fixed movement trajectories, like most machines in commercial gyms. Unfortunately. And they felt a joint discomfort was higher with the fixed movement trajectories than with the more free movements. when you force the body to move in a certain movement trajectory that may not suit your anthropometry. It doesn’t suit your individual body structure. That is not necessarily bad, but it’s a risk because if that doesn’t suit your body structure, then you’re probably limited in how much volume you can tolerate doing that specific movement.

And if you have more freedom of movement, then the brain, the motor cortex, the part of your brain that governs movement is much better able to change the movement trajectory a little bit and shift just a little bit of the stress away from from the elbow in that position where it otherwise would start to hurt. in the end based on this new study and the previous meta analysis of the total literature up until that point, we can say that we have quite strong evidence that machines and free weights are equally effective to build muscle and pretty much equally effective to build strength, at least on the exercise that you test. Free weight exercises might have a little bit better carryover to other movements and sports.

But the difference is marginal and not significant in most studies. In terms of joint discomfort, by far it matters the most that the individual exercise in question, regardless of whether that is a machine or free weight, suits your body structure. But overall, I do think it is beneficial to use exercises that allow for a high freedom of movement, all else equal, so that your body can move more naturally in a way that suits your body structure.

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About the author

Menno Henselmans

Formerly a business consultant, I've traded my company car to follow my passion in strength training. I'm now an online physique coach, scientist and international public speaker with the mission to help serious trainees master their physique.

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