Now hear this (if you still can after that loud workout music)

Justine Lee of St. Paul loves the rush she gets from throwing punches to the beat in her kickboxing class. But she doesn't love the thought of what that blaring dance music is doing to her ears.

"There are times when it's overly loud," she said. In her hourlong class, the instructor wears a microphone and screams over the music. To avoid getting blasted, Lee stands far from the speakers.

Fitness instructors have long used music to motivate their classes, but with the growing popularity of high-intensity workouts, some gym-goers are noticing that their gyms are getting louder. It's not just music. Functional movement workouts like CrossFit that involve tires flipping, large weights crashing and heavy ropes pounding the floor can produce explosive sounds with intense vibrations.

The chorus of voices calling for an end to deafening sounds at the gym includes audiologists, health professionals who treat those with hearing loss. They warn that regular exposure to excessive noise can lead to tinnitus (ringing in the ears) or even a loss of hearing.

Cycling classes and other full-throttled sessions are louder than they were a decade ago, according to a study last year by Australian researchers.

That's not exactly music to Deanna Meinke's ears.

She's an audiology professor at the University of Northern Colorado and the co-director of Dangerous Decibels, a public health initiative to raise awareness about how to prevent noise-induced hearing loss.

Generally, adults can tolerate sounds of 85 decibels — equivalent to the sound of a busy street corner — for up to eight hours.

"Anything louder than that and our human ear's tolerance rate goes way down," Meinke said.

A normal conversation registers about 65 decibels.

In the high-energy fitness world, music plays a vital role in pumping people up.

"In terms of a gym, we're talking about something that motivates people and distracts you from the agony that you might be feeling," Meinke said. "It's been discovered as a useful tool. The trick is to balance that. How do you get people motivated without blasting it?"

The inner ear has tens of thousands of fragile hair cells that move and respond to every sound we hear, Meinke explained. "If the sound is too loud and too long, it can break the tiny filaments that hold them together," she said. "It can cause the hair cell to break open and die."

Once a hair cell dies, it's gone for good, and the ear doesn't regenerate new ones.

At the Firm, a Minneapolis gym known for its club-like atmosphere and demanding workouts, the spin classes are popular and the bass is jumping. Kelly Miyamoto, who co-founded the gym in the '80s when aerobics classes were popular, said no one knew back then about the health hazards of a noisy workout.

"People now are much more savvy about what they do," she said. "We've all discussed it in the industry and the younger people seem to be much more aware of it. They have access to knowledge and information at their fingertips. We didn't have that."

There are now smartphone apps that measure sound in decibels, making it possible for any gym-goer to record the noise level.

Although the Firm sells earplugs, only three people in the class wore them.

Miyamoto said she had her ears checked a few years ago and she did not have any hearing loss. Still, she ordered custom-made earplugs — the kind that professional musicians wear while performing. "You hear the sound like it is and it has that extra layer of protection," she said.

Life Time Fitness offers earplugs, too. The Chanhassen-based national fitness chain also has a policy on acceptable noise levels.

The policy calls for a 90-decibel limit, in compliance with the regulations set by the Occupational Safety and Health Administration, said Amy Henderson, a Life Time spokeswoman. In addition, the club hired an outside agent last year to perform surprise tests on the noise levels. She said the findings showed that Life Time's cycling classes registered 63 decibels, on average.

"That is what we set as a safe standard for our clubs," she said.

Kirk Johnson is group fitness music manager for Life Time, where he also teaches cycling, total conditioning and yoga. He's also a drummer for Prince.

In his role as music manager for the fitness club, Johnson comes up with playlists for other instructors, making sure the beat is in sync with the steps in the workout. The playlists are a powerful tool, he said. "Because you're going there, it's a 5:30 a.m. class and you're waking up. But if the music is driving and the instructor is energetic, that's going to get you up and your heart rate will be elevated."

At the same time, he said, he recognizes that there can be too much of a good thing.

"You can't have the music so overpowering that you can't talk over it. You have to be smart as an instructor and gauge that. You'll have those who love loud music because that's the drive. So you really have to find that medium."

Even for him, sometimes it gets too loud. That's why he, too, has taken to wearing custom-made earplugs.

Allie Shah • 612-673-4488