Foot beds and orthotics are a great way to really improve the performance of any cycling shoe. Our feet are designed for walking/running, adapting to uneven terrain, absorbing shock, and providing propulsion. Needless to say, our feet have not evolved around cycling. Fortunately, cycling footwear and insoles have evolved around our feet.
When the foot lands, it pronates (think arch collapse, forefoot splays out) to absorb shock. Some pronation is a good thing. This is the result of the foot reacting to the ground and the position of the lower leg and hind foot. As weight is progressively applied, the tibia internally rotates and weight is transferred from the hind foot to the midfoot. The foot becomes a “loose bag of bones” at this point. It absorbs impact and conforms to uneven surfaces. Too much or too little pronation is a bad thing.
On the opposite end of the spectrum is supination. During normal walking, supination occurs when weight is shifted from the midfoot to the forefoot. This occurs as the foot switches from deceleration (shock absorption) to acceleration (progression towards toe off). The tibia externally rotates and the foot goes from that “loose bag of bones” to a rigid lever. This allows for efficient propulsion and keeps power generated by the legs from being robbed by the foot when explosiveness is needed.
Pronation-supination is a continuum. Some people fall more on one end or the other. In cycling, there is much less need for pronation than there is with walking or running. What would be considered a normal amount of pronation with these activities would be considered excessive for cycling resulting in inefficient power transfer to the bike under the same conditions.
Orthotics control the position of the foot and cause it to function in a more supinated position when intended. This is useful for sports like skiing and cycling. There are really two options when it comes to orthotic – custom and prefabricated over-the-counter (OTC) devices.
OTC orthotics will mostly benefit casual riders with a relatively neutral foot type. Not all OTC orthotics are created equal, however. Look for devices with an aggressive rigid arch. If you can take the foot bed, place it on the counter top, and completely compress the arch with your thumb, it’s no good. You standing on it, is no contest and it is nothing more than a squishy pad, robbing you of energy transfer. My favorite OTC orthotic is Superfeet (no affiliation) although there are other decent ones out there (Powersteps, Sole, etc).
There are many times when a one size fits all approach simply won’t do. Custom orthotics are preferred when treating pathology to the lower extremity, when there is a presence of more significant deformity (excessive pronation/supination for instance), or for serious cyclists who really want their setup dialed in.