Preventive Insights On Shoewear And Bike Fit For Cyclists
- Volume 25 - Issue 10 - October 2012
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What You Should Know About Bike Saddle Adjustments
Most bike fits will start with the seat (saddle) height. The general rule is that the leg should be almost fully extended when the foot is at the bottom of the pedal stroke so the tibia is in about 30 degrees of flexion in comparison to the femur. The pelvis should be level and the foot should be in a neutral position for this in order to avoid excessive plantarflexion. One local bike fitter describes imagining mud on the bottom of your shoe and wiping your foot in a posterior direction to remove the mud. This is the appropriate position of the foot at the bottom of the pedal stroke.
The saddle height and 30 degrees of tibial flexion are somewhat variable among riders of different sizes and also different riding styles. However, this height provides a good starting point that one can adjust in the future.
Adjusting the bike saddle height may be the most important aspect of the bike fit and may play the biggest role in injury prevention. Having the seat too low will place a significant amount of pressure on the knees and place them in an inefficient position to help apply pressure to the pedals. This is why many people with a seat that is too low are struggling up hills or moving slowly on flat ground.
After setting the saddle height, one would proceed to address the fore/aft or front to rear positioning of the saddle. Most fitting systems will use some variation of looking at the position of the front of the knee to the metatarsals or to the spindle that attaches the pedals to the crank arms. Historically, bike fitters used plumb lines to measure the position of the front of the knee relative to the foot. Now bike fitters may use lasers to do this measurement.
Then one would move the seat forward or backward to place the knee in the appropriate position over the foot. Sometimes, due to short femurs, the bike seat cannot move far enough forward to place the knee forward enough over the foot. When this occurs, one may exchange the seat post for a seat post with a forward bend to push the seat farther forward or exchange the saddle for one with longer rails.
The reverse also holds true for long femurs that may put the knee in a position that is too far forward.
A Pertinent Guide To Handlebar Positioning
The next part of the bike fit involves finding the appropriate size handlebars, which are usually around shoulder width. The height of the handlebars will vary greatly and is usually tied to riding style. Faster, more aggressive riders or racers will tend to have the handlebars lower, often below the level of the seat. Less experienced and less aggressive riders, or those riding long distance bike tours, will often set the handlebars higher to achieve a more upright riding position.
The setup of the handlebars may slightly alter the saddle height and fore/aft positioning as there should only be slight pressure on the hands when fit appropriately. Excessive pressure on the hands quickly leads to pain during a ride lasting a couple of hours.
To complicate things further, handlebar height may vary during a given season. Early season rides may have a more upright posture but as the season progresses and flexibility and strength improve, the handlebars may drop to a lower position for more aggressive riding by the end of the season. In addition, too much of a forward lean may also place excessive strain on the lower back.
Pain in the knees and feet are two of the more commonly reported complaints in cycling. One can relieve anterior knee pain by moving the saddle slightly higher and in a more posterior direction. Posterior knee pain may respond to dropping the saddle lower and in a more anterior direction. Medial and lateral knee pain are often a result of foot position, and can be affected by the pedal to bike shoe interface.