Setting up a bike for a proper fit is critical for a good cycling experience and prevention of injuries. One of the most important and difficult thing to get right is the height of the saddle.
If the saddle is set too low, the hamstrings aren’t engaged forcing the quads to be primarily used. This makes pedaling less efficient and more tiring. Set the saddle too high and the hamstrings overpower the quads at the bottom of the pedal stroke causing a stressful snap in the knee. This can lead to a repetitive stress injury of the knee. There is a sweet spot where the muscles are balanced and work efficiently together.
Unfortunately, this sweet spot is small and difficult to hit. Research has found that a knee angle between 140 and 150 degrees at maximum knee extension (MKE) is optimal. For a typical rider this translates to about a saddle height within a 3/4” (2 cm) range to achieve this optimal knee angle.
In addition, the angle of the foot in relation to the pedal must also be considered as changes to the foot angle directly change the knee angle. So as the saddle starts to get too high, most riders will compensate by pointing their toe which increases the foot angle and decreases the knee angle.
We evaluated hundreds of fitting sessions from professional bike fitters to come up with a proprietary algorithm that makes a recommendation on the amount to raise or lower the saddle based on these measurements.
The algorithm looks at both the knee and foot angle to determine the optimal saddle height. Riders that pedal with their heel down (a low foot angle) are recommended to have a higher knee angle than those that pedal with their toe down (a higher knee angle).