We're no longer in the heyday of HIIT (high-intensity interval training) and CrossFit. Now, low-impact and functional fitness workouts are all the rage for American adults.

Why it matters: As longevity becomes a primary health focus, more adults are prioritizing workouts that help them in the long-term by being easier on the body and improving strength and flexibility.

• More than one-third of Americans say they prefer low-intensity training exclusively, according to recent data from exercise booking platform Mindbody.
• And almost 29% of consumers said they exercise for a long and healthy life in 2023, compared to 20% the year before.

Flashback: About 15 years ago, we "went through an era [of] high-intensity interval training," from Insanity to CrossFit, says Nima Alamdari, honorary professor of sport and health sciences at the University of Exeter.

• When done too quickly, those kinds of high-impact workouts can lead to back, knee or ankle injuries, Alamdari says.

Now, Pilates, in particular, is taking off.

• Pilates — a low-impact exercise that benefits balance, flexibility and core strength and can help athletes recover from injuries — was the most popular ClassPass workout of 2023, with booking reservations up 92% from 2022, according to data shared with Axios.
• And Yelp searches for Pilates increased 25% from the previous year.

"Functional fitness," a kind of movement that more than half of those surveyed by Mindbody say they engaged in, is a relatively new wellness phrase.

• It doesn't have an exact clinical definition, but it generally means exercise that advances physiological function, Alamdari tells Axios.
• Mindbody defines it as a "type of strength training that prepares the body for day-to-day activities like squatting, bending, pushing, and lunging."
• Unlike stationary bikes and certain gym equipment — which often involve singular repetitive motions — functional fitness exercises typically work multiple muscle groups via different planes of movement, done at low or high intensity, and with or without equipment.

Functional fitness and low-impact exercises like Pilates are "particularly important" for people 40 and older because that's the age that muscle mass and function can start to decline, says Alamdari, who's a clinical advisory board member of functional fitness workout company Pvolve.

• In a 2024 small healthy aging study Alamdari helped conduct, researchers found that compared to their peers who simply followed the CDC physical activity guidelines, perimenopausal and menopausal women who specifically performed Pvolve exercises had greater lower body strength and muscle mass.

What we're watching: Alamdari says more exercise research is in the works, including studies he's working on related to recovery and injury prevention in runners.