Military recruits are prone to a high occurrence of lower-extremity overuse injuries such as stress fractures. Now a study published in Medicine & Science in Sports & Exercise (the journal of the American College of Sports Medicine) suggests the use of shock-absorbing insoles in footwear worn by these soldiers.
Researchers with the School of Sport and Health Sciences at the University of Exeter, Exeter, United Kingdom, analyzed insoles worn in military boots during running.
The insoles were tested for stiffness after being mechanically degraded by being repeatedly struck in the heel area to simulate running at various distances. Each type was then worn by recruits in biomechanical testing to determine how much each insole was able to cushion the blow of running. More testing was then done to see how the insoles influenced the angles of the foot, ankle, knee and thigh before and during contact with the ground.
The insole most likely to prevent injuries is made of 6 millimeters of soft polyurethane foam attached to a stiffer, vinyl foam footbed with a raised heel. It demonstrated the greatest absorbency, was the most effective in slowing the occurrence of peak impact force and reduced the bend in the ankle during each step.
The standard issue insole for Royal Marines offered no benefit.