FILE - People exercise at a park in Buenos Aires, Argentina on June 2, 2021. (AP Photo/Natacha Pisarenko, File)

You won’t find dumbbells or weight machines in the gym Sean Keogh runs. At Calisthenics Club Houston, it’s all about training with body weight.

“That’s all we do,” Keogh said — but that’s enough to keep new members coming through the doors, excited to learn moves like handstands and pullups.

Keogh and his members have plenty of company. These days, content creators, independent gyms and megachains alike are promoting calisthenics, an age-old form of fitness that uses little or no equipment and instead relies on body weight for resistance.

In July, President Donald Trump even reestablished the Presidential Fitness Test, intending that youth across the country will again practice old-school exercises like situps, pushups and pullups.

It’s little surprise that these no-frills moves are making a comeback in our over-scheduled society, said Anatolia Vick-Kregel, director of the Lifetime Physical Activity Program at Rice University. “We don’t always have time to go to the gym,” she said. “This is what you can do at home or in your office.”

Another reason might be economic, said Michael Stack, an exercise physiologist and president of the Physical Activity Alliance, a coalition of groups that promote physical activity. With no equipment required, calisthenics-based programs are affordable for exercisers and profitable for gyms that offer them. Plus, people may have gotten used to exercising with few accoutrements during the pandemic.

“This trend has been building,” Stack said. “The pandemic definitely accelerated it.”

How effective are calisthenics?

There’s plenty of research to suggest that calisthenics can improve everything from muscle strength to aerobic conditioning, Vick-Kregel said.

“Body weight is phenomenal,” she said.

But there are limits to its effects, said John Raglin, a professor of kinesiology at the Indiana University School of Public Health, Bloomington. “It can be effective,” Raglin said. “But I think the idea that it can or should replace the use of even simple equipment is wrong-headed.”

Sometimes, Raglin said, using equipment can actually make exercises simpler or safer to perform. Many people, for example, do pushups with improper form.

“If you’re not strong enough or you have joint issues or arthritis, then lying on a bench and using small hand weights can actually be safer and more practical,” he said.

It all depends what your goal is

Beyond safety, people looking to significantly increase their strength or muscle size will likely see more dramatic results if they use weights, Raglin said. Doing so “utilizes more of your muscle and generates more force than you could otherwise,” he explained.

Lifting weights also damages muscle tissue in a way that can be productive, as muscles grow larger through the body’s repair process. Over time, though, it may take larger amounts of weight to keep seeing gains. Progress plateaus as the body gets used to exercises it’s done before.

It’s not impossible to grow muscle through calisthenics, Vick-Kregel said; it’s just harder to continuously level up exercises for sustained progress without increasing external weight.

“After you’ve done a couple workouts of squatting with your body weight, your body’s going to need external load to get stronger or to build muscle tissue,” Stack agreed.

In other words, if you’re after bulging biceps, you may need more than calisthenics to get there. But if you’re just looking to get moving and improve your health, your body is probably enough.

Particularly for the roughly 75% of Americans who aren’t meeting federal physical activity guidelines — which call for at least 75 minutes of vigorous or 150 minutes of moderate aerobic activity a week, plus two strength-training sessions — calisthenics are a great option, Stack said.

“Body weight is the simplest apparatus you can use,” Stack said. “I would encourage anyone who’s not exercising to start exercising with just their body.”

How to begin a calisthenics routine

First, assess your current fitness and mobility, Vick-Kregel said. With the help of a mirror, workout buddy or trainer, see if you can do exercises like planks, pushups and squats with correct form. If not, look for modifications, such as doing pushups from your knees.

Once you feel confident with the fundamentals, aim to perform calisthenics in 10- to 30-minute chunks, two to three times a week, she suggested. (For a little more structure, you can consult the The Five Basic Exercises Plan, or 5BX, a classic calisthenics program developed by the Royal Canadian Air Force in the 1950s.)

Progressively increase the duration and intensity of your workouts as you get fitter. “Gradual progression is critical,” Vick-Kregel emphasized.

As you get more experienced, though, calisthenics can be performed at high intensity. Keogh maintains that these exercises are not just for beginners. There are plenty of ways to increase the difficulty of body-weight exercises over time, making them both highly challenging and effective, he said.

For doubters, Keogh has a blunt message: “Try it.”

FILE - Over 2,000 members of the Women’s Army Auxiliary Corps (WAAC) take part in a mass calisthenics exercise in Fort Oglethorpe, Ga., on May 15, 1943. (AP Photo/B.I. Sanders, File)

FILE - People exercise at a park near the Temple of Heaven in Beijing on April 2, 2024.(AP Photo/Tatan Syuflana, File)