The feet skeleton, its arches are formed in the shape of arcs that bear on three points. This facilitates the body steadiness while body reclines on any curvilinear surface. Besides, this contributes into extinguishing of inertia forces that emerge under movement condition. Distance between support points as well as the arches heights depend on ability of sole fascia and muscles of transversal arch for strain and extension.
Support function. 2/3 of all energy the organism expends on vestibular apparatus functioning and on sustaining the body in vertical stable position. It is defined by location of body’s General Centre of Gravity (GCG) relatively to CG of bearing base support triangle. Exactly this condition underlay deformation development for support arches, and afterwards other types of deformations follow. Support arches are represented by transversal arch (points 2-3) and external longitudinal arch (points 1-2).
The arches heights in their uppermost middle part vary in the following range:
* 2-3 mm under the heads of metatarsal bones for 2-nd and 3-rd toes in transversal arch.
* 3-4 mm right at the centre of longitudinal external arch.
If muscles are in hypertone, this height reaches order of magnitude about 5-6 mm. If and when another support points appear under the arches, this evidences of their deformation and attests the defection of the feet functional characteristics.
Absorbing (Amortizing) Function – extinguishing of vertical component for inertia forces. They emerge over movement and reach magnitude F = m(5 – 20)g, which must be extinguished to F = m(0.5)g. It could be attained by means of muscles located in internal longitudinal arch and subtalar joint. There are still other contributors to extinguishing process – lower limbs’ joints and spine, protecting the brain from persistent concussion. There is no support under internal arch, and no artificial support must be put under it. To extinguish inertia forces it is imperative to have big air gap and definite time, however small, to extinguish velocity. When muscles are weak and subtalar joint pronates, the amortizing role must be played by orthotics. If muscles are strong, they are in need of relaxation.
Factors and Agents of Infraction for Internal Arch Amortizing Function:
• descending of external arch vertex. The fourth support point emerges, relative to which the screwing moment appears. This moment swerves subtalar joint, for what reason the air gap under internal arch decreases, its amortizing function becomes more low.
• “valgus-effect” – turning of heel bone inwards, thereafter pronation of subtalar joint takes place
• difference in lower limbs lengths leads to valgus-effect (turning outwards) of heel bone, and then subtalar joint pronates
If muscles are weak, the heel bone is swerving and turning under shorter limb. In case of strong muscles this happens under longer limb
• walking with toes turned outwards
• if muscles are strong (muscles hypertone ) the arch does not amortize either
Stroke (Impact) Function. The five-phase step cycle describes step period. Its terminal phase constitutes so called rift-over and toes’ push or stroke to shift body CGC and to gain possibility for the next step. This conclusive phase is performed by the strongest muscles of human body – by feet toes muscles. When transversal feet arch and toes are deformed, the functioning of lymph pumps and venous-muscles pumps is distorted, thus veins become diluted.
Pump Feet Function. Skeletal muscles of human body never stay at rest or at repose. Muscles are preliminary constricted, and they undergo constant micro-vibrations. The body GCG is constantly oscillating either. That is how the following real factors are sustained: muscles pump function, venous and capillary blood circulation. The sequence of muscles contraction in walking process contains biomechanics of muscles pump working. These pumps provide and ensure metabolic processes and proper energy functional condition.
Reflex Function. Feet soles, feet mechanical receptors, feet reflectoral receptors carry through and insure reciprocal connection between human organism and environment. Besides, all these agents participate in defining the body position in space, in exchanging of energy and in sustaining the energy balance and equilibrium in the human organism.