FOOT FUNCTION AND WALKING

Walking is a true pendulum-like gait. The body’s centre of gravity rises and falls over a stiff, supporting leg creating an exchange of kinetic and potential energy (like an inverted pendulum). The mechanics of the foot and ankle are integral to the pendulum effect, providing a stable but mobile base of support for the the body to ‘vault’ over via a system of 3 rockers or pivots operating in the sagittal plane (see diagram). The leg is also acting like a pendulum during ‘swing phase’ as it swings back and forth from the hip Joint. Any restriction in the sagittal plane due to compromised foot or ankle function will cause compensations to occur in the frontal and transverse planes (toeing out, bow legs, over pronation etc.). The most common sagittal blocks are in the ‘ankle rocker’, due to reduced functional range in the ankle joint, and in the ‘forefoot rocker’, due to hallux valgus/hallux rigidus. The 3 rockers create the classic heel-toe action that characterises walking in humans.

 

The key feature required in a ‘walking shoe’:

 

• An anatomical toe box; wide, flat and foot shaped (toefreedom) to restore and maintain the ‘forefoot rocker’ and the stabilising function of the toes.

Sole thickness, cushioning, heel height etc. are negotiable based on the terrain, climate, BMI and age of the walker.

 

HUMAN LOCOMOTION

 

• The biomechanics of human locomotion can be explained by the physics of pendulums and springs. Humans have essentially four locomotive strategies available: walking, jogging, running, sprinting.

• These locomotive strategies become progressively less pendulum like and more spring like as speed and gravitational loading increase and contact time decreases (see diagram).

• Each locomotive strategy has energetic and biomechanical consequences i.e. metabolic cost and risk of injury.

• Skillful human movement is characterised by adopting the locomotive strategy for a given speed and terrain that maximises economy while minimising injury risk.

• Movement strategy selection is influenced by several factors including habit, conditioning and accurate sensory feedback about the external environment.

 

WALKING

 

 

RESTORING FOOT FUNCTION

 

Restoring foot function begins with restoring foot ‘form’ or shape. Just as the foot becomes shoe-shaped from wearing shoe-shaped shoes, the foot will become more foot-shaped by wearing foot-shaped shoes! The adaptation of the human body to the mechanical loads and stresses placed upon it is known as ‘Wolff’s law’ in biology. The key ingredients to restoring foot function are daily exposure to GRAVITY and MOVEMENT (the forces that create anatomical adaptation), and FUNCTIONAL FOOTWEAR (providing the ‘space’ for anatomical adaptation).

 

FUNCTIONAL FOOTWEAR DEFINED

 

1- Foot-shaped design (=toefreedom): A shoe should mimic the ‘fan-shape’ of a healthy unshod foot i.e. the widest part of the shoe should be the distance from the base of the great toe to the tip of the smallest toe (the toe-box). ‘Wide’ shoes that are not foot shaped are just as harmful to foot function as narrow shoe-shaped shoes

 

2- Flat sole: The weight–bearing area of the sole should be flat to the floor to provide maximum surface area

 

3- No toe-spring: The toes can only perform their stabilising role if they are in contact with the ground

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HOW TO USE FUNCTIONAL FOOTWEAR

 

Based on simple physics, the demands on the movement system increase as the forces acting on the body increase (bodyweight) and/or stability decreases e.g. two feet to one foot to just the forefoot. Start using your functional footwear with the movements on the left and slowly progress towards the movements on the right.

References
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