Marathon testing: load cells and running shoe technology

This weekend, an estimated 41,000 people will set off to run the Virgin Money London Marathon, little knowing the part load cells will play in their progress.

Whether an international athlete, elite runner, club superstar or fun runner dressed as a superhero/nurse/furry animal, every single participant will depend on their footwear to give them a firm footing over all the 26 miles and 385 yards of the course.

 

The impact of running

Running places various strains on the runner’s feet due to the heel-to-toe action, and the impact of the foot hitting hard pavements repeatedly. A quality running shoe needs to:

• Reduce the impact force transmitted through to the bones and joints by providing sufficient cushioning for the foot
• Keeping its shape during running to provide support where required whilst still dissipating shock

Load cells can be used to measure both the force and displacement values.

 

Better traction for better results?

The last thing a marathon runner needs are slippy shoes, especially around the various surfaces encountered on the streets of London. Load cells are used to measure the traction (the translational friction coefficient) between different shoe sole materials and running surfaces.

On the other hand (or foot!), a shoe doesn’t want to be too ’sticky’ either. A team from the University of Calgary Human Performance Lab used load cells to test their hypothesis that increased traction wouldn’t increase performance. However, they found that:

“Under ideal conditions where large-scale slipping was not an issue, increasing the available traction of the running shoe provided the athletes with increased performance.”

 

Timings and endurance

Durability is crucial for a running shoe. The world’s top runners will zip around in about 2.5 hrs for elite men and 3hr for elite women. For the vast majority of runners on Sunday, the chaps will be running for at least 4.5hrs and the women closer to 5hrs. That equates to an average of a 10 minute mile for men, and a 11 minute mile for women. Add in all the hours and hours and hours of training, and that’s quite a battering for the average running shoe or (heaven forbid) designer trainer

Load cells are commonly used in sports shoe machinery endurance testing. A team in Germany adapted a prosthetic foot test machine to test for endurance:

“A motion capture system tracks the motion of the shoe and the machine. Forces and moments are acquired with a 6-DoF load cell… The machine is controlled by a single component load cell that has acceleration compensation. Therefore force data of the machine is especially at higher speeds less noisy compared to the 6-DoF load cell due to inertia effects.”

All elements of a running shoe need to be durable to continue to support the foot. A study by a team from the Dept of Metallurgy and Materials, University of Birmingham showed that running shoe midsoles made of EVA foam were liable to damage and would increase the pressure placed on the plantar by up to 100% after just 500kms of running.

“Scanning Electron Microscopy shows that structural damage (wrinkling of faces and some holes) occurred in the foam after 750 km run. Fatigue of the foam reduces heelstrike cushioning, and is a possible cause of running injuries.”

 

Which running shoe is best?

Always a hot topic, which a group of researchers from the Queensland University of Technology tackled with a study into “In-Shoe Pressure Distribution for Running in Various Types of Footwear”. As the team explained:

“Discrete pressure sensors were used to examine the influence of shoe construction on the local forces under the foot. Measurements were performed at eight locations under the feet of 22 subjects wearing 19 different models of running shoes. Mechanical properties of shoe soles were assessed with an impacter device. Pressure distribution, ground reaction force, and acceleration data were collected simultaneously during running at 3.3 m/s.”

 

Top running shoe tips

If you’re a recreational runner looking for the best running shoes, there’s some excellent advice on the London Marathon website.

 

Best foot forward!

And if you’re running this year to raise money for charity, we wish you all the best. Between you and the other runners, the money raised by the annual event could reach the £1billion mark this year. We who are about to sit back on the sofa and watch, salute you!

 

Load cells for your research

If you need specialist load cells for your research project, call us. We design, manufacture and ship our own load cells to researchers across the UK and beyond, and can create bespoke load cell systems for your specific requirements.