By Dr Karen Soo BSc(Med)Hons MBBS MSpMed FACSP, Sport and Exercise Physician
The parts of a shoe
The two main parts of the shoe are the upper, which covers the foot, and the sole, made up of the outsole, midsole and insole. The midsole is one of the most important features in a sports shoe. It is the section between the outsole and the upper and is involved in shock absorption and control of foot motion. Encapsulation of air or silicone gel can enhance the cushioning effect of the midsole eg “HydroFlow” and “Mogo” in Brooks shoes, “Gel” and “Solyte” from Asics and Nikes’s “Air”. Stability features can be built into the midsole to control excessive motion.
Foot mechanics during walking and running
Excess pronation, or “rolling in” can change the mechanics of the leg during walking and running. It can be associated with patellofemoral or “kneecap” pain, Achilles tendon problems and “shin splints”.
Excess supination, or “rolling out”, also associated with a high arch, can result in poor shock absorption from impact with the ground.
Assessing the shoe
Check your shoes for the following:
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1. The shoe should have a heel counter which is firm, to provide stability for the hindfoot. This can be tested by compressing the heel counter with the thumb and index finger and checking for resistance to compression.
2. The midsole and heel counter can be assessed by pressing firmly on the outsole of the heel from below. The midsole should spring back quickly, but if it returns slowly, or the whole heel counter becomes squashed, it may be time to get a new pair of shoes.
3. Torsional stability can be tested by observing if the shoe maintains its form when the forefoot and rearfoot of the shoe are rotated in opposing directions.
4. Shank stability is present if the shoe is able to bend at the foot’s metatarsophalangeal joints (“knuckle joints”). Problems arising if the break point occurs at the midfoot or not at all include calf or toe tendon injuries.For the pronator
In addition to the above features, the shoe should have a stability feature such as a dual density midsole, which is a higher density section of the midsole usually indicated by a coloured area.
For the supinator
These people are said to have poor shock absorption, but most of the high quality sports shoes available have good cushioning midsoles.
Neutral walker/runner
These shoes can have mild stability features or none at all, with a cushioning midsole
Summary
- Consider a shoe specific for your sport or activity.
- Is the heel counter firm and stable to compression?
- Is the midsole firm and does it spring back when compressed?
- Is the shoe stable with torsional twisting?
- Does the shoe bend at the toe joints?
- How old are the shoes – consider replacing after 6-12 months or 500-800 km (depends on the degree of impact over time).
- Assessment and advice about your individual foot mechanics from a sports physician, sports physiotherapist, podiatrist or specialist running shoe store is helpful.