Cycling builds cardiovascular fitness and muscular strength. Though riding a bike would seem to work only your legs, it also can engage your upper body and core muscles if you use good cycling form and stay aware of those muscles during your ride.
Riding a bike primarily works your lower body. Over time, you’ll see the greatest gains in muscle strength and tone in your lower body from cycling regularly. Pushing the pedals on a bike engages your quadriceps, the large muscles in your thighs, and climbing hills or using bigger gears will require more effort from these muscles. The glutes are also engaged when the pedals down.
If you use cycling shoes and “clipless” pedals, you can also pull up on the pedal during each stroke. This upward motion works your hamstrings. Cycling also uses the calf muscles to continue the force generated by the quadriceps and hamstrings down through the foot and toes, especially during the bottom portion of the pedal stroke when the foot is closest to the ground.
The upper body is not used extensively when riding a bike, which is why professional cyclists typically have amazingly defined and strong legs, but small upper bodies. The arms and shoulders are primarily used to pump the handlebars from side to side during climbing on steep hills. Some arm, back and shoulder strength is still required for cycling, however, if just to be able to hold good cycling form over many miles during longer rides.
Good cycling form also requires strong core muscles. Holding yourself in the correct body position for cycling entails using the core to keep the back flat, shoulders down away from the ears and stomach slightly sucked in. This body position is the ergonomic ideal and will prevent fatigue and injury from many miles on the road, while also allowing for the maximum use of the leg and glute muscles.
During your ride, direct your awareness to these different muscles to feel how they are each used during the motions of cycling. Staying aware of the muscles will help you over time to engage them properly during cycling, to maintain better form and to build strength. Spinning classes and weight training in the gym are also great ways to build your strength for cycling, especially if you focus on the muscles mentioned here. Building core strength is especially important not just for cycling, but for the demands of everyday life, so take extra time to work on those muscles.