Neither has a proven edge. A 2023 meta-analysis of 13 studies and 1,016 people found no difference in muscle growth between free-weight and machine training, and no difference in overall strength gains when each group was tested on the equipment it trained with. You get strongest on the tools you practice with, so choose by goal, comfort and access. Most people do well with a mix.
The short answer: both build muscle
Here's what the research supports so far:1
- Muscle size: no meaningful difference has been found between free weights and machines.
- Strength: you get better at what you practice. Barbell training builds barbell strength, and machine training builds machine strength.
- Your choice: pick what you'll use consistently and can load safely, and combine the two if you can.
What does the research say?
The largest analysis is a 2023 systematic review and meta-analysis by Haugen and colleagues.1 It pooled 13 studies that directly compared free weights with machines for at least 6 weeks in adults aged 18 to 60. Together they included 1,016 people (789 men and 219 women). Six studies used trained lifters, seven used untrained people, and none used competitive athletes. Programs averaged about 9 weeks.
Free-weight groups mostly did barbell lifts like the back squat and bench press. Machine groups often used the leg press, chest press and various Smith machine exercises.
Muscle growth: no difference
Both kinds of training built muscle, and the difference between them was close to zero and not statistically significant.
Strength: specific to the equipment
- When everyone was tested on free-weight lifts, the free-weight groups gained more.
- When everyone was tested on machines, the machine groups tended to gain more, though not significantly.
- When each group was tested on the equipment it trained with, the gains were about the same.
One sub-analysis found that upper-body strength rose more with machines in that like-for-like comparison. Lower-body strength showed no difference.
Jumping: no clear difference
Jump height improved similarly with both. The trend leaned toward free weights, and four of the five jump studies used barbell squats, but the difference wasn't significant.
What the research can't tell you yet
- Muscle was rarely measured directly. Only a handful of studies measured muscle size, and just two used ultrasound. The rest relied on indirect estimates like skinfolds, limb circumference or whole-body composition tests, which vary a lot in how well they pick up changes in muscle.
- The studies were short, 6 to 12 weeks.
- Some results were fragile. Removing a single study shifted several of the strength and jump results.
- Specific muscles might respond differently. The authors suggested total growth could be similar while growth in particular muscles differs, but this review couldn't test that.
The ACSM's 2026 position stand, which pooled 137 systematic reviews, took a similar view.2 It found that free weights versus machines didn't change strength gains, and that there wasn't yet enough data to say whether the choice changes muscle growth.
A closer look at one trial
A 2020 randomized trial put 46 young adults (26 of them women) on either free weights or machines for 8 weeks.3 Each muscle group was trained 2 to 3 times a week with 3 to 4 sets of 4 to 10 reps.
- Biceps and quadriceps thickness increased in both groups, with no difference between them.
- Strength on the free-weight bench press, free-weight squat and Smith machine squat rose 11% to 19% in both groups, again with no difference.
- Machine bench press strength rose more in the machine group (13.9% vs 8.6%), another example of training specificity.
Free-weight sessions produced a bigger short-term rise in free testosterone in the men. Muscle and strength gains over the 8 weeks were still similar. It's one small, short study in young adults, but it lines up with the meta-analysis.
Why would they build muscle equally?
What seems to drive growth is how hard and how much you train, not the type of equipment. Muscle growth is similar across a wide range of loads when sets are taken to failure,4 and both free weights and machines let you train that hard.
The real differences are about skill and stability. Free weights move freely, so your body has to balance and steady the load. That takes more coordination and tends to show more activity in the supporting muscles. Machines guide the weight along a fixed path, which lowers that demand.1 But the review's authors noted that more activity in supporting muscles during a lift hasn't been shown to mean more growth over time.
They also speculated that machines might make it easier to push the target muscle close to failure, because your balance or a smaller muscle is less likely to give out first. That's an idea, not a tested result. For more on effort, see Do you need to train to failure?
Free weights vs machines at a glance
The first two rows come from the research. The rest are practical differences, not study results.
| Factor | Free weights | Machines |
|---|---|---|
| Muscle growth | Similar in studies so far | Similar in studies so far |
| Strength | Best for free-weight lifts | Best for machine lifts |
| Skill needed | Higher: balance and coordination | Lower: fixed path |
| Isolating one muscle | Harder | Easier |
| Pushing close to failure | Riskier on heavy lifts without a spotter | Usually simpler to do safely |
| Where you can train | Dumbbells and a bench work at home | Usually need a gym |
| Injury risk | Unclear; no good evidence of a difference | Unclear; no good evidence of a difference |
Should beginners start with machines?
They can, but they don't have to. In the meta-analysis, training status didn't change the overall result, and both approaches produced strength gains.1 The authors suggested machines could suit inexperienced lifters, since less balance is needed, but that's a suggestion rather than a finding.
The ACSM's 2026 position stand puts weight on picking training you'll stick with. It argues that tailoring a program so people keep doing it matters more than following one rigid prescription.2
A sensible path is to use machines and dumbbells for movements you're unsure about, and learn barbell basics with light weights as you go. If you split time between home and the gym, Rep Labs covers gym strength and home workouts in one app and plans your reps and weight from your training history.
How to combine free weights and machines
This structure uses the strengths of each. It's guidance, not a tested program.
- Start with one or two free-weight compound lifts, such as a squat, deadlift variation, bench press or overhead press. Strength gains are larger for exercises done early in a session.2
- Follow with machines or cables to add volume for the muscles you want to grow. Aim for at least 10 hard sets per muscle group each week, the volume the ACSM review linked to more growth.2
- Push machine and isolation sets closer to failure, and keep a rep or two in reserve on heavy barbell lifts.
- Rest longer on the big lifts. See How long should you rest between sets?
- Swap freely. If the squat rack is taken, a leg press or Smith machine squat works for building muscle.
Here's an example lower-body day built that way:
| Exercise | Equipment | Sets and reps |
|---|---|---|
| Barbell back squat | Free weight | 3 sets of 5 to 8 |
| Romanian deadlift | Free weight | 3 sets of 8 to 10 |
| Leg press | Machine | 3 sets of 10 to 12 |
| Lying leg curl | Machine | 3 sets of 10 to 15 |
| Standing calf raise | Machine | 3 sets of 10 to 15 |
When does the choice matter?
- You compete or get tested in specific lifts. Powerlifters, weightlifters and athletes tested on a barbell lift should prioritize that lift, which the meta-analysis authors also recommend.1
- You want to bring up one muscle. Machines make it easier to isolate a specific muscle, which the authors note can help with targeted muscle building.
- You train at home. You don't need a full gym. Home-based and resistance-band training both improved strength in the ACSM review.2
- You're returning from an injury. Machines can let you load one area in a controlled way, but let a professional guide the plan.
Questions people also ask
Are Smith machine squats as good as barbell squats?
For building leg muscle, the evidence so far suggests machine versions work about as well. In a 2020 trial, Smith machine squat strength rose by a similar amount whether people trained with free weights or machines. If your goal is a bigger barbell squat, though, practice the barbell squat, because strength is specific to what you train.
Can you build muscle with only machines?
Yes. In the studies so far, machine-only groups gained muscle about as well as free-weight groups. Those studies were short and mostly measured muscle indirectly, so the honest answer is yes, as far as current evidence can tell.
Are machines safer than free weights?
It isn't clear. The authors of the 2023 meta-analysis called any difference in injury risk uncertain, because the evidence comes mostly from cross-sectional studies rather than training trials. One report of higher injury rates with free weights found that most injuries came from weights falling on people, not from the lifting itself.
Are free weights more functional than machines?
That's a common claim, because free weights demand balance and look more like everyday movements. The 2023 meta-analysis didn't test daily function, and jump height improved similarly with both. If a specific movement matters to you, train something close to it.
Sources
- Haugen ME, Vårvik FT, Larsen S, Haugen AS, van den Tillaar R, Bjørnsen T. (2023). Effect of free-weight vs. machine-based strength training on maximal strength, hypertrophy and jump performance: a systematic review and meta-analysis. BMC Sports Sci Med Rehabil 15(1):103.
- Currier BS, D'Souza AC, Singh MAF, et al. (2026). American College of Sports Medicine position stand. Resistance training prescription for muscle function, hypertrophy, and physical performance in healthy adults: an overview of reviews. Med Sci Sports Exerc 58(4):851-872.
- Schwanbeck SR, Cornish SM, Barss T, Chilibeck PD. (2020). Effects of training with free weights versus machines on muscle mass, strength, free testosterone, and free cortisol levels. J Strength Cond Res 34(7):1851-1859.
- Schoenfeld BJ, Grgic J, Ogborn D, Krieger JW. (2017). Strength and hypertrophy adaptations between low- vs. high-load resistance training: a systematic review and meta-analysis. J Strength Cond Res 31(12):3508-3523.