Cycling is a highly repetitive sport with thousands of pedal strokes per hour, making cyclists susceptible to overuse or overload injuries. Ideally, we want the hip, knee and foot to operate in a straight line, and this alignment can be assessed by observing knee tracking.
With the foot fixed to the pedal (bar a few degrees of float in the cleat), and the hip relatively fixed to the saddle, an inappropriate stance width where the hip, knee and foot are not in good alignment may place torque through the knee, which can result in discomfort or injury.
Direct application of force can also improve your power production and efficiency. Since the foot is fixed, as is our pelvis width, we need to align the foot with the knee, not the other way around.
Q Factor is the distance between the outside of one crank arm to the outside of the other.
This is an important bike fit parameter as it effects your stance width, which is how far apart your feet end up being when placed on your pedals.
How to increase of decrease Q factor?
Both road and MTB cleats will give you some side to side adjustment, between 4-6mm. To widen your stance width you should place your cleat towards the inside of your shoes.
Looking to decrease your stance width? The only way to do this (without swapping out the crankset) is via the cleats, by moving them to the outside of the shoe.
Pay attention to pedal spindle length
Pedals have different spindle lengths, with Shimano and Wahoo Speedplay offering wider options for those who need a larger stance width.
Another option is to fit pedal washers or pedal extenders. Pedal washers are 1.5mm each, and you can fit a maximum of two (3mm total) and still have enough thread to safely screw in the pedal.
Pedal extenders add 20mm more width, which is quite a significant amount, although this can be offset somewhat by adjusting the cleat.
One thing to note is the huge increase in pedal spindle width between the Look-compatible Favero Assioma power meter pedals, and the Shimano-compatible ones (54mm vs 65mm). Those who need a narrow stance width may experience issues with a 65mm pedal spindle width.
Common issues with wrong Q factor
The knee is the most likely area to experience discomfort or injury with an inappropriate stance width. The most common knee pain issue when stance width is too narrow is pain on the outside of the knee, often involving the ITB, due to strain being placed on these lateral structures.
The patellofemoral (knee cap) joint can also be irritated by torque force/twisting being applied to the knee when the stance width is too narrow or too wide, causing increased compression on the medial or lateral structures under the knee cap.
Another issue may be pain or numbness on the outside of the foot as it tries to push out against the shoe.
How to address these issues?
Best is to seek a professional bikefit, self fit is possible if you have the right equipments and knowledge.
In a nutshell. Q factor is an important assessment if we want to cycle injury or pain free. Remember prevention is always better cure.