Though many have trusted a static fit for their fit needs, a dynamic fit that includes real-world power conditions provides a more accurate portrait of how your body interacts with your bike while riding. The benefit? Comfort and efficiency.
Static Bike Fit – All measurements taken in a static/fixed position. For example, the cyclist is placed in a foot down position then measured, foot forward position then measured, etc.
Dynamic Bike Fit – All measurements are recorded via motion capture camera while the cyclist is pedaling under resistance. The video is analyzed, and changes are made to the bike.
In discussions with other premier bike fitters, most say that there is somewhere between a 4°-6° difference in knee angles between a static bike fit and a dynamic bike fit. Breaking this down, people riding bikes will tend to move either forward or backward in the saddle when under a heavy load. Moving forward or backward places the rider in a different position than when sitting neutral in the saddle as with a no-load condition found in a static fit.
Most bike fitters, including myself, agree that a dynamic bike fit is best. The drawback is that this is a longer and therefore more expensive process. But the advantage is the fitter can view and evaluate the rider pedaling under real world loads. The bodies angles are recorded in real-time using a motion-based capture camera running at a high enough frame rate that smooth pedal rotations, for analysis without blurring. The riders’ motion is recorded to a file which is then opened in a computer analysis program such as Dartfish. Exact angles can be identified under different loads (if taken) and further precision in the bike fit can be achieved.
A dynamic bike fit will put the cyclist closer to their optimal position than a static fit. For an even closer and more precise fit, you must also consider the time of day of your races and get a bike fit at this exact time.
Does all of this matter? Even with a static bike fit, a good bike fitter will get their client into a better position than by having no bike fit at all. But the same good bike fitter will get their client into an even better and near perfect position with a dynamic bike fit. On average, a dynamic bike fit is about $100 more than a static bike fit. This is because with a dynamic bike fit, the fit needs to be accomplished first, then, the bike fitter need to spend extra time copying the dimensions from the fit bike (Guru, Retul, Purely Custom, Shimano) machine onto the riders bicycle. Of course, this is assuming that the bike fitter pays attention to detail as well as knows how to correctly and accurately copy measurements from the bike fit machine to the actual bicycle.
Another option employed by a good bike fitter is to use the clients bicycle on a Computrainer and motion-based cameras and analysis software. In this example, the bike fit is a little more difficult to perform but once done, all updates have already been made to the clients’ bicycle. Since there are several variables at play here, a good bike fitter will know how to use them to help you with the perfect fit. The only caveat is that you, the client, need to find a bike fitter who understands these methodologies and can use them effectively.