Burning thighs or even lungs while cycling is an acceptable nuisance and a sign of a good, intense day in the saddle. Pure nuisance, on the other hand, are burning soles of the feet. What is commonly known as a runner's issue also robs many cyclists of the fun of cycling. And this feeling has nothing to do with the current temperature! For some, the issues along the soles of the feet appear after hours, while for others, burning and aching soles and numb toes are annoying after only minutes. These problems can generally be remedied, but unfortunately, such foot pain stems from very different causes. They can be located from the calf muscles and Achilles tendon to the arch of the foot and the plantar fascia to the transverse arch in the forefoot. Sometimes burning feet are also accompanied by numbness and localized pressure pain.

All symptoms related to burning soles have one thing in common: they stem from overuse and/or incorrect loading. Theoretically, even a non-ergonomic seating position can trigger the problems. To rule this out, a bike fitting with appropriate guidance is always worthwhile. Much more often, a combination of several factors proves to be the cause. For example: the shape and possible pre-existing conditions of the foot, its position and pressure distribution in the shoe, interaction of the feet with the insoles or special inserts, and the positioning of the foot or shoe on the pedal. The following four triggers are most likely: 

Irritation or Inflammation of the Plantar Fascia (Plantar Fasciitis): This flat tendon runs from the heel along the entire underside of the foot to the forefoot. Together with the arch of the foot, it forms a kind of bowstring. Like its tendon, the plantar fascia is stretched when the foot is loaded and the arch is pressed down. Unusually long periods of standing, walking, and cycling can irritate the contact points of the fascia at the heel bone and transverse arch. But even localized pressure in its center can cause symptoms, including burning (see below). Common issues such as flat feet and fallen arches favor such symptoms and complaints. 

Compressed Metatarsal Bones (Metatarsalgia): Numerous nerves and blood vessels run from the area of the toes through the midfoot towards the ankle joints. Through constant up and down movement, tired feet can sink and thus narrow the channels for these nerves and arteries. This applies to both the longitudinal arch and the transverse arch. The same can happen with shoes that are too tight. Especially with shoes that are too narrow at the level of the ball of the foot, the transverse arch is compressed sideways, virtually artificially pressed into a narrower radius. Additionally, this is exactly where the power transfer to the pedal takes place, so the bones are heavily and unnaturally loaded. Both together can also lead to the mentioned metatarsalgia. 

Cramped Toe Flexors: The opposite can also lead to pain and burning in the arches and soles. Shoes that are significantly too wide feel like you’re continuously slipping on the ground. The subsequent reflex originates evolutionarily from times when humans were still barefoot on the ground or in trees, trying to grip with their toes. Since this has no effect in a shoe, the gripping reflex intensifies to cramp-like clawing. The responsible flexors of the toes or their tendons also run along the sole of the foot to the calf muscles and are thus permanently tense, although hardly any pressure is transferred through the toes while cycling. This cramping of the toe flexors can also be perceived as burning soles. 

Concentrated Pressure Distribution on the Pedal: Special cycling shoes with stiff soles, and not just those made of carbon, can relieve the metatarsal bones. Biomechanically optimal is a pressure transfer from the metatarsophalangeal joints to the pedal axle. During bike fitting, explicit attention is paid to the correct positioning of the feet on the pedal or the correct alignment of the cleats on the sole of road bike shoes or MTB shoes. Deviating foot placement and especially with very soft soles, for example from sports shoes, leads to the axle or other parts of the pedal pressing into the sole and not transferring the pedaling energy evenly like cycling shoes. This feels to the foot as if standing barefoot on a thin rod. The pressure transfers to areas of the sole that are not made for it or even to the plantar fascia.

This is also the reason why Ergon insoles support the foot more from the inside and less through an elevation in the sole. They keep the ankle joints in a natural position without pressing into the plantar fascia from below. The same support principle is used by a surprisingly large number of elite road cyclists. It is based on transferring pedaling energy through exactly the same three points as when walking. The big and little toe balls and the heel are aligned at the same height, while a gentle upward curve towards the inner ankle prevents the foot from buckling towards the crank when pedaling. 

Such an ergonomic insole for cycling also makes a shoe that is too soft much firmer, mitigating the mentioned pressing of the pedal axle compared to a classic footbed. Nevertheless, especially for frequent riders or on longer distance rides, a real cycling shoe with a correspondingly stiff sole is recommended. Whether you use clipless pedals or ride the shoe without cleats is secondary. If you wear cleats, make sure to adjust them properly and allow for some residual freedom of movement. 

If you can rule out overuse of the plantar fascia in everyday life and pre-existing foot conditions as the cause of chronically burning soles while cycling, and if the feet are biomechanically correctly positioned with the ball of the foot on the pedal axle, inadequate footwear is usually the only remaining trigger. Special cycling shoes with their stiff soles distribute the pressure on the pedal over the entire foot, thus reducing the risk of incorrect loading of the metatarsal bones or the large fascia along the sole of the foot. When it comes to fit, the width of the shoe in the forefoot area is more important than its length on the bike. If the problem with burning feet still persists, corrective insoles are the next step. As described, they should not be too excessively shaped! Regular stretching of the calf muscles and Achilles tendon, as well as strengthening exercises for the ankle joints and toe flexors, can also help or be used prophylactically, emphasizes our ergonomics expert Dr. Tofaute.