Remember “Buns of Steel”?

Almost a quarter-century after the exercise video made its VHS debut, the obsession with having firm, toned glutes is back.

Classes such as “Best Butt Ever” and “Gluteus Maxout” pepper the schedules of gyms, while concept studios targeted toward building the behind spread across the country. Fit-fluencers such as Sam Paparo and Cassey Ho have built whole YouTube and Instagram brands on their backsides.

Gone are the willowy, flat-bottomed, Spandex-wearing workout queens of the early ’90s. Instead, today’s gluteus craze celebrates the oft Instragrammed curves of Kim Kardashian, Beyoncé and Nicki Minaj and seems geared toward confidence and strength, as well as sex appeal.

“The focus is on curves, and that appeals to everyone,” said New York City personal trainer Bec Donlan.

She said she thinks that we’ve reached a more pragmatic moment in fitness culture. Her example: The average woman can’t transcend genetics to look like Heidi Klum, but she can create a firm behind.

“Rather than everyone being desperate to have that stick-thin model bod, which genetically is not possible for 99.9 percent of the population, we are more accepting of what our bodies are realistically capable of,” she said.

Strengthening one’s behind is not just about looks, said Stephen Pasterino, a New York physical therapist.

“The butt and the hips are the drivers of everything you do, whether you are an athlete or not,” Pasterino said.

“Without a strong butt, the chances of getting hurt are sky-high. It supports your back; it supports your hips; it drives you through motion and accelerates motion; it helps to prevent injuries in the knees, even in the shoulders.”

Many trainers frown on the traditional forms of glute toning — squats, dead lifts and lunges — because without proper form, the strain is transferred to your back and legs.

“You can squat for days, and if your glutes aren’t firing, you’re building up your quads,” Dolan said.

She recommended putting a resistance band around your ankles and doing 20 sidesteps to one side, then 20 to the other. Then do squats from a wide-legged stance with the band above your knees. Follow with single-leg dead lifts: Put the band under one foot, hold it with the hand on the same side, then bend and straighten.

She also cautioned against overtraining. “Your butt needs to rest and recover after a workout so it can build muscle. If you’re constantly working on one muscle group, that will lead to a constant state of fatigue, meaning zero results and an unbalanced workout.”

Pasterino said that even if you choose not to become an Instagram icon, your back and knees will thank you.