Moderate evidence

Machines and free weights build muscle equally well.

In practice

Use whichever you'll do consistently and can load safely. A machine is not a lesser exercise, and it's often the better choice when balance, a sore joint, or training alone is the constraint.

What it doesn't say

Strength gains are somewhat specific to how you train — test yourself on a barbell and barbell training will look better. Free weights may also carry advantages for balance and sport transfer.

Source

• 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 Science, Medicine and Rehabilitation. doi.org/10.1186/s13102-023-00713-4