Does spinning lead to bulky quads?

We’ve heard this comment about eight million times (maybe you have, too): “I love to spin, but I don’t want to bulk up my quads.”

While no one who said this to us wanted to be quoted, we’ve literally heard such comments as, “I can’t fit into my Rag & Bone jeans anymore.”

So amid the growing chatter and concern that this popular cardio workout may be a great way to torch calories, but at the expense of thicker thighs, we wanted to know, is this an urban fitness myth spun out of control? Or does spinning really lead to bigger quads?

We interviewed fitness expert and cycling guru Kristin Kenney, as well as top instructors from rival studios Flywheel and SoulCycle, Holly Rilinger and Kym Perfetto. Their findings? Indoor cycling does not necessarily lead to larger legs—but the following six factors could be behind any perceived bulk. Learn what they are now. —Rosa Levitan

Your Genes

Chromosomes play a major role in whether or not you can fit into your skinny jeans, say both SoulCycle’s Perfetto and Flywheel’s Rilinger (pictured here).

“The size of your quads is highly dependent on genetics. I’ve had strong quads since I was about eight years old,” says Rilinger, who’s muscly from head to toe.

In fact, most spin instructors don’t have her kind of definition!

Your Body Type

Are you wispy thin or athletically built? Body type is a factor, no matter what your workout is, says Perfetto (pictured here). Consider the three main body types—endomorphs, ectomorphs, and mesomorphs—and which you might be.

Ectomorphs are generally tall, thin, and lanky and have a hard time putting on muscle. Endomorphs and mesomorphs, however, respond much more quickly to resistance training and build muscle with relative ease. Doing any sport could create this change.

Your Spinning Starting Point

Your starting point on a spin bike plays a big role in whether and how you build muscle. Perfetto points out that a 115-pound fashion model who’s never cycled will gain muscle from it, while a bodybuilder or a super athletic type may see the opposite effect.

These changes may be short term, says Perfetto. “If your jeans are initially tighter after a few weeks of cycling, don’t freak out,” she says. “Your quads might bulk up a bit at first, but the overall amount of cardio will balance it out.”

Why? Developed quads help you burn more fat overall. The large muscle group responds quickly to activity and increases muscle-to-fat ratio within the body, which in turn increases your metabolic rate.

Photo: Cityroom.blogs.nytimes.com

Your Diet

Confirming what we might already suspect: “Cycling doesn’t make your legs bigger, but bread and pasta do,” says Rilinger. In other words, increased activity doesn’t mean you can disregard healthy eating habits.

Turns out, weight gain corresponding to increased physical activity is very common, with new riders falsely thinking that because they just torched 650 calories on a bike, they can eat whatever they want. (Sorry!)

Your Recovery

Fitness expert Kristin Kenney, who’s the creator of HIGH GEAR cycling classes at Equinox, says dealing with a boost in appetite due to increased spin sessions can be tricky, too. “New riders may experience a large calorie deficit and lack proper recovery, resulting in an unusual level of hunger,” she says.

Chowing down on Pinkberry after class won’t keep you full, and you’re likely to crave more high-calorie foods later. Kenney recommends eating a small meal of four ounces of lean protein and complex carbohydrates post-workout to stay full and ensure muscle recovery.

Your Cycling Form

While spinning’s a “quad-dominant” workout, to quote actor Max Greenfield (aka Schmidt from “New Girl”), that doesn’t mean only the quads are worked. That’s kind of like saying push-ups only work the arms.

Spinning also activates your abs, hamstrings, glutes, and back muscles. You know when your instructor says to use your abs? Use your abs! And when they say not to grip the handlebars? It’s to activate muscles in the back and glutes. When you focus on pulling up with the pedal (rather than jamming it down), then you’re drawing on the hamstrings.

Riding incorrectly not only leads to injury, but may cause unwanted muscle growth, says Perfetto, whose legs are sculpted but not a bit bulky.

She’s one more reason why we won’t let quad-bulking concerns slow us down on the bike: Have a look at the bods of most spin instructors—they’re lean-legged spinning machines, and they’re prob on a bike way more than you. (Not that there’s anything wrong with strong, sexy quads!)

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