Bike riding is a low-impact activity that can help you burn calories. Although the bike works the major muscles of your lower body, that doesn't mean that your legs will get big. In fact, you may actually lose weight and gain a lean appearance by adding biking to your fitness routine.
Every person has a different body type. When you bike, you can build muscle. The Mayo Clinic explains that the more muscle you have, the bigger engine you have for burning calories during exercise and after exercise. However, you can get bigger or bulkier-appearing legs if you're adding muscle with bike riding but not losing fat, due to poor nutritional choices. If your diet is unhealthy, you may be adding muscle on top of the fat you already have, which can result in bigger legs.
Hill training is the only way that you can add size to your legs, because propelling yourself uphill makes great demands on your body. The resistance of the hill challenges your hamstrings and quadriceps. When climbing a hill you build muscular endurance and can add size to your legs. However, the only way to add noticeable size is if you're hill climbing on a very regular basis and exhausting your muscles.
When riding your bike on flat ground, you can burn calories and create lean muscle to avoid bulky legs. The Harvard Medical School explains that when riding at a fairly leisurely pace of 10 to 12 miles per hour, a 155-pound person can burn 7 calories per minute. Adding more speed to your ride burns even more calories and can help you melt fat and reduce the size of your legs.
Stretching after your bike ride can help you lengthen your muscles for a sleek appearance. Stretching will help elongate the muscles of your body. Hamstring stretches, like a runners lunge or a forward fold, can lengthen the backs of your legs. Standing quadricep stretches can help to open the fronts of your thighs after a ride.