Riding a bicycle is an excellent form of physical activity. Whether mountain or road biking, cycling can strengthen muscles, burn calories and improve cardiovascular health. For many cyclists, the purchase of a bicycle can be a big decision. Bikes can range in price from a few hundred dollars to several thousand dollars. Factors such as terrain, training volume and level of competition all play a role in the type of bike that is best suited for an individual rider.

Perhaps as important as the type of bike is the fit of the bike to the rider. Even the best bike, not properly adjusted to the individual rider, can lead to discomfort, fatigue, poor performance, and/or injury. Common injuries associated with a poorly fitting bike include back and neck pain, numbness or pain in the hand/wrist, knee pain, foot pain, and numbness or tingling in the feet and toes.

A “bike fitting” is designed to assess the rider and his/her relationship with the bike. Bike fitting can be as simple as making a few measurements at rest, or as advanced as monitoring while riding with video analysis in a wind tunnel.  Whether fitting is performed at a local specialty bike shop or on a trainer with video in a bike fit specialty sports clinic, the goal of any bike fit is to optimize performance while avoiding positions that lead to discomfort or injury. Computer software also helps many higher-end bike shops achieve ideal fit. The amount of emphasis placed on performance, comfort, and/or injury prevention should be tailored to the cyclist, taking into account his/her goals and preferences. 

While the availability of more advanced bike fitting may be limited in a particular area, information about where to get a quality bike fitting can be obtained from a sports medicine specialist in your area, a physical therapist with knowledge of cycling mechanics, or at a local specialty bike shop. Simple measurements and adjustments can be done by most people with knowledge of bicycles and cycling mechanics. However, more advanced bike fitting and specific adjustments to aid in performance and injury prevention are best handled by professionals who have advanced training or certification. Biomechanical factors such as muscle balance, posture and joint alignment, and optimal cycling form are important to consider for accurate assessment. It is important to note that changes made to any one of the measurements can affect the other measurements, so a comprehensive approach is recommended. Once a basic fit is achieved, measurements can be adjusted to individual comfort and riding style.

Although the details of a complete bike fit are beyond the scope of this forum, one should be aware of a few key measures/adjustments that should be part of any basic bike fit:

1. Frame size:  Determined by height and/or inseam.
2. Saddle height:  Formula based on length of inseam. Position should allow for full leg extension with a slight knee bend at the bottom of the pedal stroke and designed to give rider the most power output for the least amount of energy. The easiest way to achieve this without measuring is to use the “hip rocking” method, where the saddle is raised to the point where a rider’s hips start to rock from one side to the other at the bottom of the pedal stroke; the seat should then be lowered until the hips stay level throughout the pedal stroke.
3. Saddle fore-aft:  Measurement made to align the front kneecap over the middle of the pedal to obtain neutral knee position.
4. Saddle tilt:  Typically level. A carpenter’s level can determine this.
5. Reach:  Most individualized or flexible adjustment. Determined by top tube length, stem length, stem angle, and handle bar height and bend.  Ideal position can vary, but in general, the rider should be in a comfortable position with the lower back flexed to approximately 45 degrees or a lesser angle if more comfortable, arms extended, and elbows slightly bent to allow for easier breathing, improved weight distribution, handling, and decreased strain on neck and low back.

AMSSM Member Authors: BJ Deimel, MD and Chris Madden, MD

Reference
Madden C, McCarty E, Putukian M, Young C. Netter’s Sports Medicine. Saunders Elsevier; 2010.