Overlooked and under appreciated. That’s the lot of the cycling insole. Far from being an “out of sight, out of mind” item though, the insole is another important component of fine tuning a bikefit.
The standard insole that comes with most cycle shoes (with some notable exceptions) looks like a bit of an after thought. Generally quite flimsy and offering inferior performance after just a month or two. Allowing the foot to wash around inside the shoe reduces the sense of connection to the pedal and diminishes power delivery. By contrast a quality insole helps all the above and improves the feedback to the pedal stroke by enhancing proprioception or movement sense. Knowing just where your foot is helps switch the whole motor chain on to a smoother pedal stroke.
As power output increases more pressure is imparted to the region around the inner ball of the foot. A good insole will contribute with the shoe to distribute this load and enhance foot control, promoting power transfer to the pedal. At the same time it will allow adequate ventilation and will not crowd the the foot. When fitting it is an item we frequently change with immediate positive effect on the sense of “connectedness” and power transfer to the pedals. I will almost always consider a different insole before advancing to other cleat modifications such as wedging. In addition, just as in walking, it will help us with alignment of the foot/knee/hip axis.
Some effective off the shelf insoles can be had for around $40. I have come to use Superfeet (the yellow version) and Soles (the grey version) the most when fitting simply because the product works, they are readily available and they accept small modifications quite readily. Custom insoles, like orthotics, will run to significantly more money but allow particular fitting for a difficult foot.