Wednesday, February 7, 2018

Power to the Pedals: Using Foot Pressure Mapping to Optimize Cycling Fit & Performance

Cycling is ultimately about how much power we can get to the pedals. Everything we do from training to improve power to buying stiffer shoes and bikes to optimize power transfer is designed to get more power into the bike and push us forward that much faster.  But what if the key link in this system -- the shoe/pedal interface -- was actually the weak link? More often than not the shoe/pedal system is an overlooked variable that offers a fairly easy means of making sure more power makes it out of our legs and into the drivetrain.    

For example, Mike came in for a basic hour-long fit session. His main concern was that he was experiencing high saddle pressure.  So the session focused on dialing in his position and choosing the right saddle using saddle pressure mapping. He is riding in comfort now and is pain free, a great result.  

We had Mike come back in for a follow up session and explore more options for perfecting how he is getting power into the pedals.  Turns out Mike never really had his cleats setup before, he is using a non-cycling orthotic inside his shoes, and 3mm of cleat spacers had been installed on his right shoe because of what he had been told was a leg length discrepancy.  All of these issues alone could contribute to some shoe/pedal problems, and all of them together are almost certainly going to raise concerns.  

After getting Mike setup with shoe pressure mapping, we captured a baseline measurement.  

                                            Mike's Baseline Measurement

Immediately a few issues appeared -- a relatively small area of the shoe is absorbing pressure; on the left, almost all pressure is on the big toe and the ball of the foot; pressure is relatively low; pressure is quite unstable; and, critically, the left/right distribution (the red wave is left pressure) shows relatively little pressure is making it onto the left shoe.  The result is all of this is that although is saddle pressure was massively improved the multitude of issues with his shoe and pedal setup left the critical point of power transfer with room for improvement.  

Mike has medium height arches but they collapse significantly under load.  To correct this, the first intervention we made was to replace his insoles with cycling specific insoles.  This included better arch support, and also allowed his heel to fit more snugly into the back of the shoe. The results of the next pressure run are significant: Pressure is distributed over the transverse arch of the foot; peak pressure went up meaning force to the pedal went up; stability improved with more pressure concentrated on the forefoot; and pressure on the big toe went down.

                                               Mike's Insole Pressure

At this point, however, things are still not perfect -- pressure is still too high on the ball of the foot for the right side.  We noticed a forefoot varus on the both feet, and guessed that without support, the ball of the foot was collapsing inwards creating the pressure visible in this picture. Mike has a varus on both sides but his big toe on the left foot is pointing down quite a bit and pressure on the left appears to be good without that extra support.  

Post-varus correction, the right foot is much more balanced, with the pressure peak on the ball of the foot disappearing.  At this point, we are close but his cleats still had not been setup. The ball of the foot was actually set so that it was in line with the pedal spindle, resulting in pressure that was too far forward on the shoe.  And it turns out that Mike’s cleats were actually as far forward as they could go. We moved his cleats back 1cm and ran foot pressure one last time.

                                            Mike's Final Measurement

Pressure is balanced across the center of the forefoot and, most significantly, left and right pressure have similar force curves.  More balanced, more stable, more powerful. 

Using foot pressure in the context of this fit provided the critical last bit of data to help ensure that the changes we made were translated into more force on the pedals.  As we can see with Mike, adding a foot pressure component to a bike fit is critical for ensuring optimal performance.