The benefits of strength training are seemingly endless. For starters, since lean muscle is more calorie-hungry than fat, building a little extra brawn can ramp up your metabolic rate. And strength training has also been shown to have other less outwardly-noticeable effects, like reducing resting blood pressure, enhancing heart health, tanking bad cholesterol and upping the good kind, and even promoting bone density, according to research published in Current Sports Medicine Reports.

At many gyms you have two options for getting that strength training in: free weights (barbells and dumbbells) and weight machines (all those contraptions you typically sit down on). Both weight machines and free weights have perks and downsides—but weight machines seem to get a lot of hate from the fitness community.

Is one approach to muscle building really better than the other? We asked the experts for the lowdown.

Weight Machines

Weight machines force you into a fixed track of motion, explains Sean De Wispleaere, master trainer at MBSC Thrive and owner of Sean D. Thrive. (Picture someone sitting in a shoulder press machine, pushing the handles, which move only up and down.)

This makes using weight machines beneficial if you’re a beginner, De Wispleaere says. “Staying in a fixed track of movement can help you learn how to pattern some complex exercises, like the squat and deadlift,” he says. You’d perform both of those moves on a Smith machine, which has a barbell fixed to steel rails.

Additionally, they can help you truly isolate certain muscles, meaning you work only one or two muscles at a time. This is helpful for bodybuilders looking to hone in on specific muscle groups as much as possible in a given workout, along with anyone recovering from an injury that needs to avoid working certain parts of their body, according to De Wispelaere.

The issue is, if you don’t fit a machine just right, you could be forcing your body to move in an unnatural way, says De Wispleaere. And that’s a recipe for injury down the road.

Plus, if torching max calories is your goal, using weight machines won’t give you the biggest burn for your buck. “Since you’re not often engaging multiple muscle groups at once, the effect on your metabolism is smaller than it would be with free weights,” explains De Wispelaere. After all, performing seated bicep curls demands a lot less of your body than performing curl-ups or a compound free-weight movement like a curl-to-press.

Free Weights

On the flipside, free weights allow you more flexibility and freedom in how you perform an exercise, according to De Wispleaere. Since the weights aren’t on a track or cable system, you need to use more muscles than just the ones you’re specifically targeting in order to keep the weight stable. “This causes you to work harder overall and build more well-rounded strength,” he says. (Picture someone pressing two dumbbells up overhead. The dumbbells wobble side to side and front to back, engaging the small muscles all around the shoulder joint. Plus, you’ll engage your core to maintain your posture and balance.)

And because you’re recruiting additional muscles when using free weights, you’re giving yourself a metabolic edge. While the individual effects might be small, the cumulative effects of hitting more muscles with each move and each workout mean you burn through more calories, while further enhancing your strength, control, and stability.

Related: Should You Lift Full-Body Or Bodybuilder-Style?

While free weights allow you to move in a way that’s more natural for your body, that freedom also means there’s plenty of room for you to perform an exercise incorrectly, which puts you at risk for aches, pains, and injury, Di Wispleaere says. So when lifting free weights, using proper form an appropriate weight need to be top of mind.

The Verdict

Weight machines do come in handy in some cases—especially for beginners who need to build a foundation of strength, or anyone who needs to lay off an injury—and they can certainly be a part of a body-building style strength-training session. But ultimately, De Wispleaere prefers and recommends free weights.

As long as you use lift safely, using free weights will build well-rounded strength and a fit physique more efficiently.

Pin this infographic to keep the pros and cons of each strength-training style top-of-mind: