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Using hysteresis, loading and unloading tests produced by an Instron 8000 Series system to
determine the damping behavior of the sole area of shoes
Comparing what you wear on your feet with the suspension on a Formula One racing car may seem a
step beyond reality, but they're not a million miles apart. Both pound round the track at speed,
absorbing the impact of contact with the ground. Runners absorb two or three times their body
weight at their heels; basketball players absorb as much as eight times their own weight. Like
a racing car, feet need the right suspension.
Adidas is one of the world's leading names in sports footwear and they treat the design and
testing of their shoes as seriously as any racing manager. One of their latest sports shoes,
the EQT Solution, is built on a concept that Adidas calls The Feet You Wear. The design allows
the foot to move naturally, protects it where necessary, and enhances the athlete's performance
wherever possible. It means an effective cushioning system to protect the heel from impact
forces and enhance the athlete's performance during push-off.
Science in Sports Shoes
This advanced suspension system for sports shoes requires a relatively soft visco-elastic
system under the heel, absorbing a high amount of energy during impact, while under the forefoot,
a relatively soft elastic material is needed that doesn't dissipate energy. For this design,
Adidas uses a visco-elastic AdiPRENE material in the heel at the point of impact and an elastic
AdiPRENE plus material for push-off in the forefoot.
Like any high-tech suspension system, this one needs thorough testing. Adidas uses an Instron®
8516 testing machine with FastTrack 2™ WaveMaker and MAX software to measure the
"damping behavior" - of the sole area of their shoes. The soles are subjected to hysteresis,
loading and unloading tests produced by the Instron 8500 servohydraulic controller. Typical
load patterns are used to determine the dynamic stiffness and energy absorption when running
and jumping in the shoes. These tests are part of a long-term research and development project
to find the optimum absorption levels.
In the future, anyone driving their feet in Adidas EQT Solutions can be comfortable knowing
that with Instron's help, a lot of energy has gone into cushioning the impact.
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