The shock attenuation characteristics of four different insoles when worn in a military boot during running and...

A study was undertaken to determine if placing shock absorbing insoles in the boots of Royal Marine recruits would attenuate the peak pressure at the foot-boot interface, when marching at 4.8 kph carrying a 32 kg (70 lb) Bergen and running at 12.8 kph in loose order plus webbing weighing 10 kg (22 lb). Four types of insoles were assessed: viscoelastic polymetric insole (Cambion(R)) polymetric foam insole (PPT(R)) Saran insole (military issue) and Sorbothane(R). There was a fifth control condition in which no insoles were used. Pressure measurements during heel strike and forefoot loading were taken using Paratec equipment with pressure measuring insoles placed in the boots. Data were obtained from eleven subjects and indicated that all the insoles significantly (P<0.05) attenuated the peak pressures generated during heel strike and forefoot loading. The performance of the four insoles in terms of peak pressure attenuation ranked in order with the best first were: Sorbothane Cambion PPT Saran. The Sorbothane insole was substantially and significantly (P<0.05) better than the other insoles in terms of attenuating peak pressures during heel strike. During running, mean peak pressure at heel strike was 494 kPa in the control condition, this was reduced to 377 kPa when wearing Sorbothane insoles (a reduction of 27%). When marching the Sorbothane insoles reduced the mean peak pressure at heel strike from 395 kPa (control) to 303 kPa (23% reduction). During forefoot loading the peak pressure attenuation of all four insoles was similar, although on average the Sorbothane insole performed slightly better than the others and was significantly different (P<0. 05) to the Cambion insole. Mean peak forefoot loading pressure in the control condition when running was 413 kPa, with the Sorbothane insole it was 367 kPa, during marching the respective mean peak pressures were 397 and 323 kPa. It is concluded that of the four types of insoles assessed the Sorbothane insoles attenuated the greatest amounts of the peak pressure generated at heel strike and during forefoot loading when running and marching wearing military boots.