Biomechanical analysis of running in military boots with new and degraded insoles.
OBJECTIVE
The purpose of the present study was to investigate the influence of degradation using repeated impacts on the ability of different shock-absorbing insoles to reduce peak impact loading during running in military boots.


METHODS
Four insole types were degraded mechanically to simulate typical running loads that occur during approximately 100 km of running. The influence of insole mechanical degradation on stiffness and impact-absorbing ability was assessed using standard test procedures. The ability of new and degraded insole samples to reduce peak impact loading during running was assessed by monitoring peak impact force and rate of loading. In addition, the influence of insoles on sagittal plane kinematics was quantified by measurement of hip, knee, and ankle joint flexion.


RESULTS
Insole mechanical degradation resulted in an increase in mechanical stiffness and a decrease in ability to reduce mechanical impacts for all test insoles. Measurements taken during running indicated that only one insole type reduced peak impact loading when new, as indicated by a significant (P< 0.05) reduction in peak rate of loading. The ability of this insole type to reduce peak rate of loading during running was maintained after mechanical degradation. This insole was also found to significantly (P< 0.05) reduce peak ankle dorsiflexion.


CONCLUSIONS
The present study identifies an insole type that reduces peak rate of loading during running both when new and when mechanically degraded. It is suggested that this indicates an insole that could potentially reduce the frequency of overuse injuries. Based on these results, this insole is recommended for use in the investigation of the practical use of insoles by military recruits, particularly for study of the influence on injury occurrence.
Dixon
Sharon J
SJ
School of Sport and Health Sciences, University of Exeter, Exeter, EX1 2LU, United Kingdom. s.j.dixon@exeter.ac.uk
Waterworth
Claire
C
Smith
Calum V
CV
House
Carol M
CM
D000328:Adult; D000842:Ankle / Q000502:physiology; D001696:Biomechanical Phenomena; D004867:Equipment Design; D005528:Foot / Q000502:physiology; D006801:Humans; D007717:Knee / Q000502:physiology; D008889:Military Personnel; D016059:Range of Motion, Articular / Q000502:physiology; D012420:Running / Q000502:physiology*; D012775:Shoes; D013848:Thigh / Q000502:physiology; D014142:Track and Field