If you noticed some extra definition in your lower body since you’ve hopped in the saddle, you might wonder, What muscles does cycling work?

After seeing years of headlines warning that “sitting is the new smoking,” it might require a little suspension of disbelief to consider that you can get in the best shape of your life while largely parked on your butt.

But that’s what cycling, a surprisingly comprehensive workout, can provide.

“Cycling builds muscle and improves endurance,” says John Gardner, an NASM-certified personal trainer. It’s a serious calorie burner, which can help you lose fat and slim down overall.

“While the most difference will appear on the lower body muscles — as most of the pedaling power comes from those muscles — your core can get toned, too,” he adds.

Cycling works your cardiovascular system as well as your lower body. Here’s how.

1. Heart

Fitness Tracker on Wrist | What Muscles Does Cycling Target

First, a good bike workout can strengthen the most vital muscle of all.

“Cycling is a cardiovascular exercise, so that means you’re going to burn calories and strengthen your heart and lungs while you do it,” says Melanie Melillo, CPT.

But in terms of the muscle groups you can see, cycling mainly works the lower body, particularly the legs. Cycling indoors with a bike that provides varying resistance can help you focus on these areas.

“When you’re an indoor cyclist, because of the resistance on the flywheel, you’ll shape and tone your legs, creating definition in your quads, calves, and glutes,” says Melillo.

2. Quadriceps

Cycling Class | What Muscles Does Cycling Target

As your legs cycle, you slightly straighten your legs to push the pedal down. That engages the quadriceps, says Gardner. Your quads are the four muscles that line the front and sides of the thigh.

As both hip flexors and knee extensors, they’re super-functional; strengthening them can help support those major joints.

And because the quads comprise the biggest muscle group in your body, building them can have visible benefits.

3. Hamstrings

Woman Stretches Beside Bicycle | What Muscles Does Cycling Target

As you bend your knees and pump away, you work the hamstrings muscles — those on the backs of the thighs — which provide force to push against the pedals, says Gardner.

And if you have clip-in pedals, you place slightly more emphasis on the hamstrings and hip flexors by more actively pulling up with each pedal stroke.

4. Calves

Man Indoor Cycling | What Muscles Does Cycling Target

As you pedal downward, the calves power the action, collaborating with the hamstrings and quadriceps to push against the pedal and stabilize the foot, says Gardner.

On the stability front, doctors and trainers often prescribe cycling to people who are recovering from knee injuries or whose knees are bothered by joint disorders like arthritis.

“I highly recommend cycling to my patients,” says Siddharth Tambar, MD, a board-certified rheumatologist in Chicago who specializes in the non-surgical treatment of neuromuscular problems.

“Cycling recruits the gluteus, quadriceps, thigh, and calf muscles. Strengthening these muscles has a stabilizing effect on the knees, decreasing knee instability, weakness, and injury,” Tambar explains.

5. Glutes

Athlete on Stationary Bike | What Muscles Does Cycling Target

When cycling, your hips rotate, which engages the glutes; they allow the pelvis to stay stable on the bike, says Gardner. The motion and resistance can strengthen this aesthetically crucial muscle group.

“The stronger your glutes are, the perkier they are,” says Melillo. “And we all know these days, the more shapely the booty, the better.”

An important note: Don’t shift your butt out of alignment to try to further engage those muscles; that can be dangerous, says Melillo.

“If you stick your butt out further, are you going to get more glute work? No,” she says. “You can actually hurt yourself. The more efficient you get at riding, the more resistance you can turn on, and the stronger you’ll get overall. Your glutes work as much as they need to work when you’re in the proper cycling position.”

6. Core

Couple in a exercising class | What Muscles Does Cycling Target

“Surprisingly, indoor cycling is a complete core workout,” says Karen Maxwell, an ISSA-certified sports nutritionist and master instructor for CycleBar in Denver, Colorado. “Your core stabilizes you; it’s your central place of balance and power. The more still the upper body is and with a tight core, the better.”

Functional Fitness

But cycling’s benefits can be more significant than any individual muscle group. “It’s really about the functional [fitness] that you bring to every other aspect of your life,” says Melillo.

“When you have more muscular endurance in your legs, you’re going to be able to enjoy the rest of your life without fatiguing as quickly. You’ll be that person who, when somebody says, ‘Hey, you want to go for a hike?’ or, ‘Let’s go for a walk,’ you’ll be able to do it because you’ll have that foundation. It brings a lot to just general quality of life,” she explains.