Machines or free weights: does either build more muscle?
This article is verified by 1 study/publication.
Machines or free weights? If you're training for muscle growth, a review of comparative studies found no clear winner. Getting stronger at a particular lift is a different question: the way you train and the way you test strength both matter.
To make sense of the results, keep two outcomes separate: changes in muscle size and changes in the weight you can lift. They are related, but lifting more in a barbell test doesn't, by itself, show that you built more muscle.
Too long; didn’t read (Summary)
- The review found no clear muscle-growth advantage for free weights or guided machines.
- Strength results depended partly on the test. Practise the lift you want to improve.
- Studies lasted 6–12 weeks, and few measured muscle growth. This doesn't prove that every exercise works equally well.
- Choose equipment to suit your goal and preferences. Combining both is an option, not a proven best approach.
What did the studies compare?
A 2023 systematic review brought together 13 studies comparing free-weight and machine-based resistance training. Eligible participants were healthy adults aged 18–60, with a mixture of trained and untrained groups. The programmes lasted 6–12 weeks. Free-weight exercises included squats and bench presses; machine exercises included leg presses, chest presses and Smith-machine movements. [1]
The review focused on machines with a guided movement path. It excluded free-moving cable systems, so its conclusions shouldn't be stretched to every piece of equipment with a weight stack. The studies also used different exercises and training programmes, rather than one identical workout repeated across every comparison.
No clear winner for muscle growth
When the researchers combined the muscle-growth results, neither free weights nor guided machines came out clearly ahead. In the chart, the dot sits close to the middle: little difference between the two. The line extends to both sides, showing that the evidence still leaves room for either approach to do better. That is different from proving that every machine and free-weight exercise builds exactly the same amount of muscle.
Free weights and guided machines were compared for muscle growth. The combined result does not clearly favour either option.
Muscle growth
Neither option clearly ahead
Dot: the estimated average difference. Line: the uncertainty around that estimate.
The line reaches both sides of “no difference”. The review cannot reliably pick a winner for muscle growth; it does not prove that every exercise works equally well.
See the numbers and study details
| Outcome | Estimate | 95% CI |
|---|---|---|
| Muscle growth | -0.055 | -0.397 … 0.287 |
0 = no difference between the groups
Results: effect on hypertrophy; Figure 4C
Source: Haugen et al. (2023)
For strength, the test mattered. Free-weight training produced greater gains when both groups were tested with free weights. Machine training tended to perform better on machine tests, but that comparison wasn't statistically clear. Some strength findings also changed when individual studies were removed from the analysis. There isn't a simple winner for every way of measuring strength.
What this means for your training
Start with the result you want. If you want a stronger barbell squat, practise the barbell squat. If muscle growth is your priority, the review gives you no clear reason to favour free weights over guided machines. Choose according to your preferences and the equipment available. You can also use both, though the review didn't test whether combining them works best.
Keep the limits in view. Relatively few studies assessed muscle growth, and their methods ranged from ultrasound to less direct measures such as body circumferences and body-composition estimates. Those measures don't all tell you the same thing about changes in a specific muscle. Short training studies also can't settle what happens over years.
When you track strength, compare your results on the same exercise and equipment. A heavier number on a different machine or a barbell is a different task, so it isn't a straightforward measure of your progress.
Sources
- Effect of free-weight vs. machine-based strength training on maximal strength, hypertrophy and jump performance – a systematic review and meta-analysis. Haugen ME, Vårvik FT, Larsen S, Haugen AS, van den Tillaar R, Bjørnsen T. BMC Sports Sci Med Rehabil. 2023;15:103. doi: 10.1186/s13102-023-00713-4. Study.