FOOT FUNCTION AND JOGGING

‘Jogging’ has been defined as ‘sub-maximal’ running, typically at speeds between 6-10mph (10-16km/h). Biomechanically, jogging is a ‘hybrid’ gait with characteristics of walking and running. Using one or both of these definitions of jogging means 80-95% of recreational ‘runners’ are actually ‘Joggers’. When jogging, the knee and hip act like ‘springs’ as in running, but the foot and ankle act as ‘rockers’ with the same heel-toe pattern as walking. Jogging places the ankle and foot rockers under considerable load compared to walking. The forces acting on the leg during the support phase double from 120% bodyweight when walking to over 250% bodyweight when jogging. The range of movement required at the ankle also increases from a minimum of 10 degrees dorsiflexion when walking to a minimum 20 degrees dorsiflexion when jogging. Both of these facts play a role in the high injury rates experienced by joggers. Any injuries or pains associated with the biomechanical compensations used during walking (e.g. toeing out, over pronation, heel pain etc.) will be exaggerated and aggravated when jogging.The knee joint is particularly vulnerable to overloading and injury during jogging when toe structure and function is compromised and jogging technique is poor *. Toe function is essential for injury-free jogging as they ‘anchor’ the foot and determine the trajectory of the knee joint over the foot during the support phase. The action of the toe flexors and extensors also play an important role in assisting the shin muscles in decelerating the foot and tibia during the entire ground contact phase. Weakness in the toe muscles is associated with anterior and posterior ‘shin splints’.

 

The key features required in a ‘jogging shoe’ are:

 

• An anatomical toe box (wide and flat and foot shaped=toefreedom) is essential to allow the toes to provide maximum stability and leverage and allow the toe flexors and extensors to assist the anterior and posterior shin muscles.

 

• Appropriate cushioning.Due to the high impact forces associated with jogging a ‘jogging shoe’ should provide an appropriate amount of cushioning to protect the heel and metatarsal bones. The human foot has evolved fat pads to protect these areas of the foot, but these pads can literally wear out from excessive loading, particularly if the jogger has a rigid shoe-shaped foot and is over 40 years old.

 

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.

 

JOGGING

 

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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