Even if you've been cycling for years, things like padded shorts, new cycling shoes, or even certain muscle groups becoming more flexible can alter bike fit, says Caroline Dawson, a master instructor for Spinning® in New York City. For optimal performance, stand to the left of the bike and adjust the saddle and handlebars to hip height. Next, bend your right arm 90 degrees, form a fist, and place it at the center of the handlebars, (the part closest to the seat); move the seat forward or back until it touches your elbow.
Finally, check your work: Sitting in the saddle with your leg extended downward, your knee should have only a slight bend (about a 25- to 35-degree angle). “You want a fairly extended leg so you are not pedaling all squished up for more power and so the knees are happier,” Dawson says. When both pedals are parallel to the ground, your front knee should be directly above the center of the pedal. If it's not, you need to slide your seat forward or back until your body is in proper alignment.