In the Netflix series “House of Cards,” ruthless politician Frank Underwood (played by Kevin Spacey) often takes out frustration on his indoor rowing machine. He’s not the only one rediscovering this old-school piece of fitness equipment: Rowing studios are popping up all over the country, much like gyms exclusively devoted to spinning or boot camps.

Part of the appeal is that rowing is a full-body exercise that devotees claim can torch between 400 and 800 calories in under an hour. “You’re getting a good full-body workout with each stroke. Plus, you’re getting great cardio, which is good for your heart. You’re really hitting it all,” says Craig Hatchett, president of D-Fine Fitness, who opened a boutique center called Row45 inside his Albertson gym two years ago. He’s since launched Row45 studios in Westbury and Rockville Centre.

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A TYPICAL CLASS

Row45 classes aren’t 45 minutes of straight rowing; participants alternate between long intervals on the machine and bursts of squats, planks and other light moves on an adjacent yoga mat. During one recent morning class in Albertson — with tunes by Bruno Mars and Taio Cruz blasting — six women glide back and forth at their own pace, though they’re encouraged to up their stroke rate by instructor Caren Rosenblum. “Keep your strokes long and strong,” says Rosenblum, walking the room to monitor each person’s progress and form. “Let your legs do the work. That’s one misconception. Most people think rowing is all arms. It’s mostly legs — 60 percent. You’ve got to power back with those heels.”

For Alena Ruvolo, 33, of Carle Place, who runs every morning, rowing is a fun addition to her routine. “I’m always up for something new,” she says. “Every time I come here, I feel so much better.” Nicole Buslik, 36, of Roslyn, has seen changes, too, since attending classes twice a week. “I have two young kids who I run after and pick up, and with this, I definitely feel stronger,” she says. “Hands down, it’s the best workout I’ve ever done.”

Yet while rowing can be intense, it’s low-impact and gentler on the body, especially the joints. That means it can appeal to all ages, fitness levels and those with injuries.

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At Metrow Fit in Merrick, co-owner Nick Benedetto has welcomed clients in their 20s and 80s, as well as folks recovering from knee and hip replacements. “Rowing really is for everyone and anyone,” he says.