Incorporating regular weight training into your running schedule is key if your goal is optimal performance and reduced risk of injury.

Slotting in weight training alongside runs can strengthen your joints, muscles, and bones, and counteract potential wear and tear that comes from repeatedly pounding the pavement, says Keith Hodges, Los Angeles-based certified personal trainer, corrective exercise specialist, and founder of Mind in Muscle Coaching.

Stronger muscles will also propel you further with each step and better absorb the impact force every time your foot strikes the ground. It’s that impact absorption that can help reduce your risk of injury, because it allows you to put more work through the muscles and less stress through the joints, says Frank Baptiste, C.S.C.S., personal trainer and founder of FranklyFitness.

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Moreover, strength workouts can help refine your mechanics and make your movement patterns more efficient. In short, “the stronger you are, the better you'’l be as a runner,” says Baptiste.

While the benefits of regular weight training are clear, what’s less obvious is the best tool to get the job done. Should you opt for free weights, like dumbbells, kettlebells, and barbells? Or stick with the fancy machines in your gym?

We tapped Hodges and Baptiste for expert input on the pros and cons of free weights versus machines, plus when to use one over the other.

The Pros and Cons of Free Weights

A big plus of free weights is they allow for more functional training than machines. That’s because with free weights, you can do multi-joint moves that more closely mimic the motions of daily life—and running.

Take the step-up, for example, in which you hold a set of weights by your sides and step up onto a chair, bench, or couch. It looks “exactly like your running stride,” says Baptiste. You can do a step-up with dumbbells in hand as a way to develop lower-body strength that directly translates to running, as you’re moving through the hips, knees, and ankles (that’s what makes it a multi-joint move).

By contrast, a leg extension machine—which involves sitting on the machine, and lifting the weight up by extending the knees—will target your quads, but those strength gains won’t have as much carryover into running. That’s because the leg machine focuses on working the quads alone and only targets one joint (the knees), making it a single-joint move, and one that doesn’t really mimic the motion of running.

The compound moves you can do with free weights—like squats, deadlifts, and lunges—can also help build balance, stability, coordination, and core control, says Baptiste. You’re standing through all of these moves (not seated on a machine), so your entire body fires up to keep you steady and upright.

Another advantage of free weights is they deliver more bang for your exercise buck, because of those advantages listed above (allowing you to work more muscle groups simultaneously and getting your entire body involved) and in general, are more challenging than machines. With free weights, Hodges explains, you don’t have anything assisting you as you complete movements, so your body has to work extra hard to stabilize and control itself through the entire range of motion of the exercise. That added difficulty means a more intense workout in less time.

There is a drawback to free weights, though: Your risk of injury can be higher compared to machines because machines guide and support you through a restricted range of motion. With free weights, it’s up to you to control your movement. “You can go out of the line of control and you can tweak something,” explains Hodges. “You’re more susceptible to injury if you’re not doing [an exercise] correctly.”

The Pros and Cons of Machines

In general, weight training with machines isn’t as functional or as challenging as using free weights. The exception is using cable machines, says Baptiste. With a cable machine, you can get into a standing split stance position (meaning, one foot is in front of the other) and do a single-arm pulls and pushes. This means you can hold positions that resemble running and those that demand stability and anti-rotation core strength. “Cables are super effective for runners,” says Baptiste. You can also do combination exercises on the cable machine, working your entire body in one exercise (like a squat to a row).

Back to machines in general, though: While they’re often not as functional as free weights, there are some legit perks. For starters, machines are better at isolating specific muscles than free weights. Say, for example, you’re looking to build muscle, specifically, and want to target your quads. Doing reps on a leg extension machine would be a surefire way to get the job done.

Compared to free weights, machines can also be more accessible to certain runners, including those who have a history of pain or injuries.

“There’s definitely a lower skill level involved with using some machines,” says Baptiste. “So if you have some history of back injuries or you experience back pain, and especially if you experience it when you’re squatting or deadlifting, then those aren’t the moves for you.” In that instance, a machine could be helpful, he explains. For example, you could do single-leg leg presses in lieu of squats.

Machines can also help make challenging moves more beginner-friendly. Take the assisted pull-up machine or the lat pull-down machine, for instance, says Baptiste. Many people struggle to do a traditional pull-up, but with these pieces of equipment, you can work on your form and build up the strength you need to do the full exercise.

Another perk of machines: They usually have instructions and illustrations that explain which muscles they target and how to use them correctly, says Hodges. That can come in handy if you need a little guidance in the gym (though it’s always best to get hands-on help from a certified personal trainer or other fitness pro).

When to Choose Free Weights vs Machines

Both experts agree that in many cases, free weights are the better choice for runners. “If I could choose one or the other, I would definitely choose free weights,” says Baptitse. That’s because with free weights, you can do more multi-joint functional movements that closely mimic running. And though there can be a higher risk of injury with free weights versus machines, Hodges recommends beginners start with free weights because they’ll help you get a sense of how the range of motion in a given movement should feel. And they’ll help you build all-over strength, especially in your core.

That said, machines do have their place, especially for people who have limitations with their form or ability level, or people whose goal is increasing the size of a specific muscle. If Baptiste had access to both tools, he’d probably still spend most of his time with free weights, but would incorporate some machine work too.

Hodges, for his part, likes mixing and matching free weights and machines because it adds variety to his routine and ensures his body is continually challenged.

At the end of the day, both types of weight-training tools can provide benefits. So while most runners are probably better off prioritizing free weights, getting any type of strength work in will benefit your running and your overall fitness level.