Most anyone who has spent enough time in the saddle knows how fragile the balance between pleasure and pain can be on a road bike. Because you ride in the same position for miles and hours, there is little margin for error when it comes to alignment. A seat that is a centimeter too far forward can cause crippling knee pain. Handlebars that are too close can wreak havoc on the shoulders and back. Muscle pain doesn’t mean you’re not cut out for road biking, it just means your bike doesn’t fit you.

A lucky few riders get lucky and find a bike that fits them perfectly right off the rack. The rest of us must rely on professional fitters to adjust our bikes so they are comfortable and efficient. Bike fits usually take one or two appointments. Typically, a fitter will measure a rider’s bike, legs, torso length and shoulders, and then set her bike up on a trainer. After a warm-up spin, the fitter looks at everything from knee alignment to hand angle, and adjusts the rider’s seat, stem, handlebars and shoes—or, if necessary, recommends new equipment.

Not all bike fitters are alike, however. Even after multiple bike fits with numerous “professional” fitters, some riders can end up in even more pain than when they started the process. Luisa Sullivan, an exercise physiologist and certified U.S.A. cycling coach, runs Davanti Cycling Coaching Center (888-348-5228; davanticycling.com), an integrated cycling coaching center that provides bike fitting, performance testing, and nutritional and training advice in Boulder. She offers these pointers for finding a first-class fitter:

Look for a bike fitter who has undergone intensive certification.
The gold standard for certification is the Serotta International Cycling Institute. Preferably, find a certified fitter who works independently. Sullivan says that some fitters who work for shops often have very little training, and too frequently steer clients to buy equipment the shop sells, but which may not necessarily suit the rider’s specific needs. She prefers that a fitter work on his own but have an agreement with a nearby bike shop to sell and mount equipment according to the fitter’s recommendations.

The fitter should ask you the main goal of your visit.
Are you looking to get aero in a Cat-1 peloton, or are you a recreational rider who simply wants to go longer without pain? The fitter should also ask about any discomfort you experience on your bike.

The fitter should measure your flexibility and posture.
A competitive cyclist rides in a far more aggressive position than someone with poor hamstring flexibility or chronic back pain. Sullivan notes that it’s a “plus” if your fitter has some background in biomechanics and coaching.

The fitter should provide a written document.
At the end of your appointment, you should leave with a document that lists the changes the fitter has made and why, along with your new measurements. The fitter may advise that you adjust some positions by “baby steps” to avoid discomfort.

Your fitter should follow up with you at no cost.
The follow-up should occur within two weeks to assess whether the changes have worked. If you experience any pain, call for a follow-up rather than making changes on your own.