Chris Smith-Professor Emeritus of Podiatry and co-founder of Superfeet Worldwide-states, “It is intuitively obvious that orthotics help the cyclist with a collapsed foot.” In this context "collapsed foot" applies to those who have some arch and are not entirely flatfooted.
For biomechanically stable feet the benefits may not seem as apparent as for those with more "collapsed" feet, however they are significant.
Dr. Smith also states; “An orthotic only works while the heel is bearing weight (from heel contact to heel off) and once the heel rises the forces acting within the lower extremity determine which way the limb/foot [tracks] (does the foot pronate or supinate?).”
It is an assumption that in the pedal stroke there is little if any weight on the heel, however there is a growing body of empirical data that there is virtually the same pressure under the heel as there is under the forefoot during the pedal stroke. In order to pedal there must be downward pressure from the legs through the ankle joint to the feet. Even if unweighted an orthotic still aligns the feet inside the shoes.
During the propulsive phase of the cycle stroke downward forces from the rider are directed through the lower leg into the rear-foot and from there forward through the mid-tarsal joint into the forefoot.
Augmenting the leverage capability of the forefoot delivers the riders energy more efficiently through the power phase of the pedal stroke.
For that to happen the mid-tarsal joint must be locked. The sub-talar joint is intrinsically dependent on a locked mid-tarsal joint. Maintaining a locked mid-tarsal joint and sub-talar neutral requires full length underfoot support. Once the feet are supported properly, the whole of the lower extremity functions as a unified mechanism, efficiently transmitting energy through the drive train into the rear triangle.
With sub-talar neutral and mid-tarsal joint locked the leverage capability of the forefoot is increased and thereby the power that can be applied to the pedals.
Once the feet are properly supported in a cycling shoe there are multiple benefits. Chris Smith has intuitively discerned; “Orthotics do help keep the foot in better alignment and consequently decrease medial deviation of the knee (during power stroke) and keeps the mid-foot static relative to the crank.” Abduction and eversion are controlled thereby decreasing the medial deviation of the knee.
Efficiency is enhanced because the forefoot does not deviate as much as it would without underfoot support and exertion from the mid-tarsal joint through the bottom bracket is more direct.
Dorsi-flexion, abduction and eversion are the three mechanisms of pronation and though the job of a biomechanically sound footbed is to control pronation. It is important to recognize the utility of each of these components during pedal stroke allows activation of different muscle groups as riding conditions require.
Underfoot support does not inhibit the functions of the feet or of the lower extremities. Biomechanically correct footbeds allow full use of all the muscle groups necessary to cycling. In fact they have been shown to increase the efficiency of the interaction with between the intrinsic muscles of the feet and the extrinsic muscles of the lower leg. Efficiency and long term comfort occur by virtue of having the full plantar surface of the feet proximal to the device so the forces applied through the feet are not dispersed through the voids under the feet, rather they are directed through the underfoot support into the pedals and etc.
A concern for cyclists is conserving energy-having enough gas at the end to complete a ride or sprint to the finish. The more efficiently the muscles are used throughout a ride, the more energy there is at the end. With the feet stabilized the skeleton bears a good deal of the forces applied to the pedals.
It is worth thinking of foot orthoses for cycling in terms of comfort as well as and/or rather than as a prophylactic.
Comfort is dramatically enhanced by having the full plantar aspect of the feet in contact with the shoe soles. This also augments proprioception-feel and balance.
With orthotic support the soft tissue is more contained underfoot thus reducing pressures on the bony prominences of the plantar surface, improving circulation, comfort and fit.
Additionally, the use of a biomechanically correct footbed/orthotic helps reduce elongation of the feet as well as the splaying of the forefeet.
A universal complaint among cyclists is a hot spot under the metatarsal heads; generally where the shoe cleat/pedal spindles are positioned. With full length underfoot support, the downward pressure exerted during the power phase of the pedal stroke is distributed much more evenly throughout the plantar surface of the feet.
For bike fitting the benefits are more than perceptible. In evaluating a cyclist from the front or from behind, the tracking of the lower extremity changes dramatically with orthotics in the shoes and without…try one shoe with a footbed and the other without. Relative to the fixed points of the bicycle like the crank arms, top tube and seat tube the differences in alignment are substantial. Once the feet are positioned inside the shoes with a good footbed there is a stable foundation upon which to fit the machine to the rider.
There has been a lot of feedback regarding the use of forefoot wedges. These can be seen to help with aligning the knees. However the use of forefoot wedges neglects the relationship between the lower leg, heel/sub-talar joint and mid-tarsal joint. It is known that there is a high percentage of forefoot valgus and significantly lower percentage of forefoot varus.
There are variations to positioning forefoot wedges. One is placing varus wedges between the cleat and shoe sole which inverts the shoe to the transverse plane. Without an orthotic the feet can still pronate inside the shoe.
Another is placing the wedge under the ball of the foot inside the shoe. The forefoot will invert and the rear foot evert. The feet can still pronate inside the shoes though it will be to a lesser degree. Unless the rider has a true forefoot varus, once the forefoot is inverted relative to the rear foot the mid-tarsal joint is rendered unstable and therefore less effective during the power stroke. The same holds true if one were to place a varus wedge under the forefoot of an orthotic; the forefoot will invert relative to the rear foot. If the forefoot is unnaturally elevated there is the increased potential for bunion deformity.
The long term goal is to reduce repetitive maladies and fatigue because of instability, improve performance and comfort.
For most riders comfort, though perhaps relative, is key.