Kettlebells are familiar to anyone who’s set foot in a weight room. But the small cast-iron orbs with handles are confusing for the uninitiated. They look more appropriate for a pirate ship than a gym, their weights are puzzlingly marked in kilograms, and their center of gravity doesn’t seem to stay put. So it’s understandable that they’re one of the most intimidating pieces of fitness equipment out there.

For personal trainer Ron Munvez, though, those who misunderstand are missing out. “You can get a really great full-body workout with a kettlebell,” said the founder of Chicago’s Tri-Fitness. “It’s a great tool.” Ron supplied us with a few reasons why you should give the gear a try.

They Make a Great Cardio Workout

What sets kettlebells apart from other weight-training equipment is that they’re meant to be used in motion. Ron said that because they don’t exert as much force on your joints as running and other high-impact activities, they’re a great way to burn calories without a lot of wear and tear on the body.

“You can get your heart rate through the ceiling doing kettlebell swings,” said Ron, who recommends doing the exercise in intense intervals with periods of rest in between. As the swinging motion gets the heart pumping, the hefty weights engage large muscle groups in the hips, core, and the body’s posterior chain, or back side.

Try This: Kettlebell Swing

Start with your feet shoulder-width apart and swing the kettlebell back between your legs. Relying on your hips for power, swing the kettlebell back up to about shoulder height. “You don’t want your lower back to round,” Ron said. “It’s a very hip-dominant exercise.”

They Work Just As Well As Typical Weights—If Not Better

“You can do squats with [them]. You can do lunges. … You can put two of them on the ground and do pushups,” Ron said.

In fact, for some exercises, kettlebells do weights one better. A bench press, for example: “If you [use] a barbell, you have both hands on the bar,” he said. “So if one side of your body is stronger than the other one, one side might push a little greater.” Bench-pressing with kettlebells ensures both sides of your body get the same amount of resistance.

Try This: Kettlebell Squats

Hold the kettlebell close to your chest with your shoulder blades together, and your feet a little farther apart than shoulder-width. Squat down, keeping a neutral spine position while ensuring that the hips move back and the knees never go beyond the toes. Pause, then lift back up with the same posture. “[Using a kettlebell] makes you squat with really good form,” Ron said.

They Can Help Reduce Your Injury Risk

“They really work on joint stability,” Ron said. “You can have somebody who … can lift a tremendous amount of weight, but can they take a kettlebell, lift it over their head, and then walk 100 yards with it without their shoulders falling off?”

The kettlebell’s unusual center of gravity can train the small muscles that surround the joints, which can help stave off injury on the pitcher’s mound, the volleyball court, or anywhere else the joints tend to be challenged.

Of course, every exercise carries a risk of injury without the proper guidance. If you’ve never used kettlebells before, it’s a good idea to take a class with an experienced instructor to ensure you maintain proper form.

Try This: Shoulder Stability

Holding the kettlebell upside down, raise your arm in the air with your elbow bent 90 degrees. Start by holding this pose for 10–20 seconds with each arm, then gradually add time and/or weight in subsequent workouts.

They Can Fit in a Studio Apartment

“You can probably have three or four different kettlebells and they’re not going to take up much room at all,” Ron said.

Kettlebells pack a lot of utility—both cardio and strength benefits—into a compact size. If you’re exercising at home, they offer a great way to get a full-body workout without overwhelming your living room. At the gym, they can help mix up a regular fitness routine.

Try This: Suitcase Carry

This simple move engages muscles on each side of the body. Using the same squatting form as outlined above, squat down, grasp the handle of the kettlebell, stand up, then walk a few paces, maintaining a steady upright posture. Repeat on the other side.

If you’re ready to get started, Ron has some recommendations for the weights you should use: 

• Women: If you’re less fit, grab a 8- to 12-kilogram kettlebell. If you’re more fit, aim for the 12–16 kilograms range.
• Men: If you’re less fit, start with a 12- to 16-kilogram kettlebell. If you’re more fit, try 16–24 kilograms.

 Photos of Ron Munvez by Andrew Nawrocki, Groupon

Check out our other fitness guides:

Five Things I Learned from Pilates

Five Things to Know About Kickboxing