Some cyclists have large legs due to the volume and type of training they perform. For example, track sprinters' legs are disproportionately large because they rely on power from their quadriceps to gain speed in short races. British track cyclist star Chris Hoy's thighs measure 27 inches -- the size of many women's waists. These elite athletes conduct workouts consisting of specific drills and strength training to develop power and size in the legs. They aren't riding for general fun or fitness. Regular cycling is unlikely to build such large leg muscles. In an indoor cycling class, for example, you spend only a few minutes at a time on hills, which is not long enough to build bulky thighs. When you are out on the road, you likely experience a range of terrains and don't spend every ride climbing mountainous hills for hours, which could lead to an increase in bulk.
Your rectus femoris is the quad that runs straight down the front of your thigh and helps flex your hips—. pull up on those pedals as well as pushing down. A great way to work that one along with your other hip flexors—and get a silkier pedal stroke in the process—is a single-leg pedaling drill. “Most people can pedal with one leg for about 30 seconds before they fatigue because the hip flexors get neglected when you use both legs because the leg pushing down is always pushing the other back up,” says Ertl.
Do It : Sit on an indoor trainer with one foot clipped in and the other unclipped and propped on a chair or stool. With the bike in an easy gear, begin pedaling at a comfortable cadence, concentrating on keeping smooth through the top of the pedal stroke (where it usually will feel hardest). Spin like that for 30 seconds. Then switch legs and repeat three to four times. Finish by pedaling easy with both feet clipped in . Build up to being able to single-leg pedal for 3 to 4 minutes each leg.