User Trial and Insulation Tests to Determine Whether Shock-Absorbing Insoles Are Suitable for Use by Military Recruits during Training

A user trial was undertaken to determine whether a shock-absorbing insole is suitable for military use. Two thicknesses of insole (3 mm and 6 mm) were studied and were issued to 38 Royal Marine recruits to wear in their military boots for weeks 12 to 30 of training. Biomechanical measurements showed that both thicknesses of insole significantly (p < 0.05) attenuated the peak pressures generated at heel strike and during forefoot loading when new (relative to a no-insole condition) and that this was well maintained after wear. This was supported by mechanical tests conducted on the insoles. It was concluded that the insoles are sufficiently durable for military use. The main user complaint was that water retention reduced the comfort of the insoles; however, insulation tests conducted with a foot manikin indicated that switching from the current-issue Saran insoles to the trial insoles would not increase the risk of recruits sustaining nonfreezing cold injuries to their feet.