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The foot is a complex structure which endures various functions. The foot is the base of support in standing, is a stable surface at heel-strike and push-off. However, during mid-stance the foot must become a mobile adapter to accept loads. The foot also has spring-like characteristics, storing, and releasing energy with each foot-stroke.
The arch is responsible for much of the foot’s functionality and the arch is controlled by the intrinsic and extrinsic foot musculature. The arch is believed to have formed for the increased demands of load carriage and running.
Origin of the Human Arch
The human foot has evolved from one similar to that of African apes, where it serves for both tree and land locomotion. This shift is likely due to the shift from trees to the ground. When walking, chimps are compromised by the absences of a rigid foot system. Specifically, apes have 1) an enlarged and permantely adducted hallux, 2) shortened lateral digits, 3) compaction and realignment of the tarsal bones to help prevent the ‘mid-tarsal break’ observed in the foot of apes, 4) the addition of a well-defined medial longitudinal arch defended by strong plantar tensile elements.
The human is well adapted for endurance running. A shift towards running encourages a pronounced Achilles tendon and the plantar aponeurosis and spring ligaments on the inferior aspect of the foot. Running also forces the toes to much larger extension forces during the push-off phase of running. The mid-stance phase of running also flattens the arch, storing recoverable strain energy on the elastic tissues. Since humans walk on only two limbs, we rely much more on our foot musculature than those who run on four limbs.
Passive Subsystem of the Foot
The passive system of the foot consists of the bones, ligaments, and joint capsules that maintain various arches in the foot. These passive structures help create the distinct medial and lateral longitudinal arches in the foot.
Active Subsystem of the Foot
The active system consists of the muscles and tendons which attach to the foot. The local stabilizers of the foot are the plantar intrinsic muscles that start and end at the foot. The global movers are the extrinsic muscles which have attachments across the lower leg.
Neural Subsystem of the Foot
The neural system consists of the sensory receptors in the plantar fascia, ligaments, joint capsules, muscles, and tendons involved in the active and passive systems. This sensation is crucial for balance, walking, and running in humans. Unfortunately, this system is quite unclear, yet they play roles in stretch response and modulation of the foot arch.
Foot Training
Most foot training and rehabilitation exercises forces on toe flexion through towel curls or marble grabs. This exercise encourages global muscle activation, not isolated strength. Therefore, creating maximal strength of the intrinsic muscles without global compensation is the goal.This training also decreases ankle instability after four weeks of training.
Controlling the intrinsic muscle activation and actively creating an arch, strengthens the arch in ~ 4 weeks. It also improves balance.
Barefoot/minimal footwear walking/training may also strengthen the foot musculature. This training may also increase the sensory input for the foot, improving the neural system and motor control.
Foot Summary
Ankle sprains, calf strains, Achilles Tendinitis, etc. need proper foot care and strengthening. Specific strengthening is a key aspect of rehabilitation of the foot and physical therapy for the ankle. Also, prevention strengthening during personal training and boot camps can help prevent bunions and foot related ankle injuries. Join the revolution of foot training today!
Reference
- McKeon PO, Hertel J, Bramble D, Davis I. The foot core system: a new paradigm for understanding intrinsic foot muscle function. Br J Sports Med. 2014 Mar 21. doi: 10.1136/bjsports-2013-092690. [Epub ahead of print]
Written by Dr. John, DPT, CSCS