Zyskowski, one of the center's owners, effortlessly bounced as the rope whizzed through the air. This particular class was cardio-focused, and the music playing was fast-paced and energizing.

"I think if we didn't have the music, the whole place would freak out," Zyskowski says. "Music is so important."

Lehigh Valley fitness experts like Zyskowski will tell you music — and just the right music — is crucial to a really good workout, no matter if it's weight-training, running on a treadmill or doing cardio exercises.

"Music helps keep you focused and motivated," says Sarah Morgan, communications manager for CrossFit Advanced.

A 2008 study by Brunel University's School of Sport and Education found that music can boost your physical endurance by 15 percent and make exercise more enjoyable. The study found that music helps you feel more positive about working out, even if you're on the brink of exhaustion.

CrossFit Advanced Fitness enthusiasts work out at CrossFit Advanced in Forks Township. Ashley Tillotson of Breiningsville works with a jump rope in the adult class. Music also helps keeps your mind engaged and focused while you're working out so you're less likely to get bored or give up because the exercise is too hard.

The pace of music affects your exercise session. A 2003 study by the University of Wisconscin-LaCrosse found that those who listened to faster-paced music generated higher heart rates and worked out faster.

Of course, everyone — from fitness experts to regular people like you and I — has a different take on what music makes us move.

Billboard Magazine found that most people like to work out to rap and hip hop (44 percent), followed by rock (28 percent), dance (16 percent) and alternative rock (12 percent).

Sarah Campbell, a personal trainer and fitness manager at Steel Fitness Premier in Allentown, has favorite songs on her playlist that go across genres and eras: "Electric

Feel" by MGMT, "Cool" by Alesso, "Five More Hours" by Chris Brown, "The Distance" by Cake and "I Don't' Hate You" by Offspring.

Even older songs can make the list. Dominic Cino, director with O2 OxyFit Gym, which has locations in Trexlertown and Macungie, loves "The Sign" by Ace of Base from 1993 for cardio.

"Off the wall I know," Cino says. "But it has a good beat."

Many Lehigh Valley fitness centers rely on Internet radio stations such as Pandora or Fit Radio.

At CrossFit Advanced, music was booming from Pandora's "dance cardio," featuring artists such as Britney Spears, Pitbull, Rihanna and David Guetta. The two classes going on then were focused on cardio exercises including rowing and jumping rope.

For classes focused on weightlifting, generally they'll play harder-rock selections. CrossFit Advanced also has classes for kids so the music, while upbeat and current, is appropriately chosen (no curse words or inappropriate content).

On Sundays at CrossFit Advanced, the atmosphere is a bit more relaxed. So is the music.

"We have Michael Jackson on Sundays," Morgan says.