by Adam Freeman - October 1o, 2023
A new meta-analysis compared the effects of free-weights vs machine-based training on maximal strength, muscle growth, and jump performance.
If the people who introduced you to lifting had a background in strength sports, they may have told you that barbells are the best (or only) way to put on size and strength.
Fortunately, that isn’t what the evidence suggests.
A meta-analysis by Haugen and colleagues, published in August 2023, sought to compare the effects of free-weights vs machine-based training on maximal strength, muscle growth, and jump performance.
A total of thirteen studies were included and analyzed. Six of these studies involved trained participants, whereas the remaining seven involved untrained participants.
As such, the results from this meta-analysis should generalize reasonably well to both new lifters and lifters who have been getting under the bar for a while.
Common exercises in the “free-weight” groups included the back squat and bench press, whereas the “machine” groups often included the leg press, chest press, and various Smith machine exercises.
Here’s what they found.
First, with regards to maximal strength, gains in free-weight exercise strength were significantly greater in the “free-weight” groups.
Conversely, gains in machine exercise strength were nominally greater in the “machine-based” groups, but this difference did not reach statistical significance.
The reason why this difference didn’t reach significance may just have been due to a lower sample size; more studies included free-weight strength tests than machine strength tests (8 vs 6).
So, it appears that gains in strength are modality-specific. If you want to gain strength in a machine-based exercise, you’re likely better off predominantly training with machines. Likewise, the opposite applies: if you’re competing in powerlifting or any other free-weight-based strength sport, it would behoove you to predominantly train with free weights/barbells. This follows the general principle of specificity.
Interestingly, no differences were found when it came to isometric strength, suggesting both machines and free weights are effective at improving overall or non-specific strength. Indeed, an isometric strength test performed on an isokinetic dynamometer is a pretty unskilled test of strength – and one that neither group would have had any experience with. This suggests that if you’re after general strength improvements, what modality you use probably doesn’t play much of a role.
With regards to muscle growth, no significant differences were found between modalities. Therefore, if you’re after muscle growth, you don’t need to use free weights or machines, exclusively. In fact, the two may complement each other very well in an effective hypertrophy program.
Finally, with regards to jump performance, free weights did significantly outperform machines for improvements in jump height improvements. So, free weights are potentially a better option than machines if your aim is to improve your jump performance.
The black bars represent improvements in the free-weight group; the grey bars represent improvements in the machine-based group.
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