Those bike people. Their music is pumping so loud you can hear it—and feel it—even when the door is shut; their instructor sounds like she's screaming at them; and they occasionally whoop. They also hoot. You watch and think, "I am not a bike person."

Everyone is intimidated, says Janet Fitzgerald, a 16-year indoor cycling veteran and a master instructor for SoulCycle in New York. She was teaching aerobics when her friends tried to convince her to come to a spin class. "I said, 'I've tried that, and I don't like it.'" Four months later, she was training to be an instructor. She says she hears stories like hers from spin converts all the time. Here, Fitzgerald answers the most common questions she gets from gym-goers:

1. What's with all the shouting?

Instructors like Fitzgerald incorporate jumps, standing runs, sprints, core exercises, arm weights and more. They need to make sure that you hear their instructions (and encouragement) over the music and the whir of the bikes. That's where their telephone operator headsets come in, amplifying their voices around the room and beyond. Fitzgerald says that there are some teachers who bark orders like a drill sergeant, but if that's not your thing, then you can try another class. The same goes for the music. "In the optimal spin experience, you're getting a DJ, a motivational coach and a fitness expert all in one package," she says.

2. Do the bikes need to be adjusted to my exact height, weight and skill level?

What matters is how tall you are and the length of your arms, legs and torso. But the instructor will explain this when they help you set up the bike; that's one of the key things they learn during certification, says Fitzgerald. Here are her rules of thumb: When you stand next to your bike, the seat should be at hip height. Bend your elbow at the nose of the seat; your fingertips should just brush the stem of the handlebars. When you sit in the saddle, your knee should still be slightly bent at the lowest part of the pedal stroke. Fitzgerald says that newbies like the handlebars to be slightly higher than the saddle for extra back and neck support (lower bars require a powerful core).

3. Do I need special shoes that lock me into the bike?

You can wear sneakers to classes in most all-purpose gyms, but specialized spin studios like SoulCycle use bikes that are only compatible with cycling shoes, and if you don't have your own, you'll have to rent a pair at the front desk. Fitzgerald claims these shoes are even safer for riding than sneakers, and physical therapists agree that they give you a better workout on the bike. Cycling shoes have hard soles that more evenly disperse the weight across the bottom of your feet. They also clip into the pedals, allowing you to work your glutes and hamstrings when you pull up during the pedal stroke. "When you wear tennis shoes, your foot is only half in the pedal basket, which makes it easier for it to accidentally slip out," Fitzgerald says. She says that sneakers' flexible soles also put unnecessary pressure on the forefoot when you push down, and overwork the quad when you pull up.

Next: How to take a time-out on the bike without falling off

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