Kinky boots: high heels testing and load cells
If you’re a fan of the 2005 film “Kinky boots”, you’ll know the story of a Northampton shoe manufacturer who needed to diversify from their core product of classic men’s brogues to survive. You’ll also know that high heels for men need to be reinforced with a metal strut to take the extra weight of the average male. The scene where an female weight heel broke under a drag queen’s foot shows the importance of testing any new shoe design to the max!
High heels and hospital admissions
As multiple studies have concluded, wearing high heels places extra strain and forces on the wearer during walking and everyday activities such as climbing stairs. In addition, in the US, over 20,000 female high heel wearers end up in hospital or with a course of treatment from their podiatrists, due to falls or sprained ankles. Up to a third of female high heel wearers also suffer permanent problems due to the increased pressure on the bottom (plantar) section of the foot.
That’s why a team of Italian researchers at the Department of Industrial Engineering at University of Bologna decided to investigate the:
“Loads, strains and stresses emerging in a pair of women’s fashion shoes during high-heeled walking with the general objective to improve the footwear safety.”
The team took a pair of high heeled shoes and replaced the heel with a pre-calibrated version with theoretically- calculated load deformation relations. This included:
“13 strain gauges, adapted to acquire axial deformation and bending in two planes. Load cells were designed to be able to acquire all possible stresses on a heel (normal, bending, torsion).
In particular:
- one Quarter-Bridge (QB) strain gage circuit for detecting the normal force (F)
- four Half-Bridge (HB) strain gage circuits to find the flexural moments in two different sections and two orthogonal directions
- one Full-Bridge (FB) circuit with strain gages at 45° for detecting the torque (T).
Similarly, strain gauges were also applied to the sole in order to determine the deformation on the whole shoe.“
The team concluded that
“Only the flexural stresses are potentially dangerous to the structural strength of the heel. Therefore, it is possible to use a simplified load cell design in monitoring the level of stress in high heels, with only four strain gages, arranged in two orthogonal planes.”
High heels and gait
A recent review of studies concludes that wearing high heels affect gait, and changes in gait changes the movements and forces throughout the wearer’s body.
“Major changes were found in the rollover function of the feet, the ankle and knee joints and the lower back, while step length and balance were compromised. An increase in heel height forces the foot in an increased plantar flexion, which in its turn increases knee flexion and lordosis of the lower back.”
Many of the studies cited used motion capture camera technology to analyse gait. This was triggered by the heel striking (stepping on) a force plate fitted with load cells in a platform.
Fashion footwear testing: five crucial tests
A company that specialises in testing fashion footwear identifies five main areas of fashion footwear that require testing:
- slip resistance, as “The risk of compensation claims for injuries due to slipping are a major concern for footwear companies.”
- heel strength
- heel attachment
- backpart stability
- strap and trim strength
All can be measured using load cell based testing rigs. Our load cells are used in many testing machines, from standard to bespoke. If you have a particular requirement, call us and together we can design a system to solve your needs.
UK company, UK load cells
We design and manufacture our load cells here in Reading Berkshire, and we have a large stock available. If you know what you need, you can order anytime on line. This often means we can fulfil and deliver faster than other load cell firms, who may be relying on imported stock.
Call us, email us, write to us or even fax us – we’re happy to help out.
