Dr Jonathan Sinclair's research into the effect that energy-absorbing insoles have on Achilles tendon injuries has been published in the Clinical Biomechanics journal.
During the course of his work with UCLan SENS Dr Sinclair came across numerous athletes with Achilles problems, but was unable to answer their questions as to whether low-cost insoles could help alleviate these.
The resulting research gives a thumbs-up to the insoles, with 11 out of 12 runners experiencing a lessening of Achilles tendon loading after they inserted them.
The experiment included 12 male runners (average age of 24) who reported running at least three times a week. In the laboratory they ran over a mat at approximately 6:40 per mile pace. The mat included devices that measured their ground reaction force, and the movement and loading rate of the Achilles tendon with and without the insole.
There was no difference in peak ground reaction force between the two conditions. However, several measures of Achilles loading rates were significantly reduced with the insoles. "This probably happens because orthotics offer further cushioning to that already provided by the shoe midsole," said Dr Sinclair. "This causes the ankle to dorsiflex more, adding to the movement arm of the Achilles, which reduces the loading rate."
Dr Sinclair tested the Sorbothane Sorbo Pro insole, but believes that "others with similar characteristics would likely have the same effects." He also notes that orthotics/insoles are not a universal injury cure for runners. "Using the wrong orthotic can lead to complications that would not otherwise have arisen," he said.
This study adds to a general trend in recent foot strike and injury papers. It appears that relatively thin-soled, low-profile shoes may be advantageous for runners with knee injuries, while thicker, softer shoes may help runners with Achilles and calf injuries.