Lifting free weights and using weight machines both make you just as strong when you test your strength in new or different ways — neither one is better than the other.

If you lift free weights, you'll get better at lifting free weights. If you use machines, you'll get better at using machines. Practicing the exact same movement makes you better at that movement.

If you measure strength with a tool that doesn’t favor free weights or machines, both kinds of workouts—free weights and machines—help you get just as strong. The difference between them is so small it might just be due to chance.

Whether you lift weights the old-fashioned way or use machines, you’ll gain the same amount of strength and muscle size—if you’re doing the same exercises and you’re a healthy adult between 18 and 60.

If you train using weight machines and then test your strength on machines, you’ll get stronger than if you trained with free weights — but only because the test matches the training. It’s like practicing basketball shots from the free-throw line and then being tested there: you’ll do better than if you practiced elsewhere.

Lifting free weights and using weight machines both help you get stronger just about the same amount—neither one is clearly better for boosting your explosive power.