Author(s): BULL, J., BROWN, N., KELLY, L., SPRATFORD, W., RADCLIFFE, C., BOUSIE, J., Institution: UNIVERSITY OF CANBERRA, Country: AUSTRALIA, Abstract-ID: 2340

INTRODUCTION:
Running is one of the most common forms of locomotion and has been widely studied, however there has been limited research into the foot’s contribution in fast running (>5m/s). In addition, females are underrepresented in fast running studies, and little is known about the foot’s contribution to fast running as we age. The foot is a complex structure and to analyse the foot’s contribution in fast running, it is important to consider the multi-articular nature of the foot. This study aims to investigate the differences in kinetics of the foot between females and males, and younger and older adults, across a range of running velocities.
METHODS:
Forty-seven healthy, active participants participated in the study; 11 older and 12 young adult females, and 12 older and 12 young adult males. All participants ran on an overground track at target running velocities of 2m/s, 4m/s and 6m/s. The younger adults also ran at their maximum running velocity (above 6 m/s). Participants wore retro-reflective markers and were filmed running on an indoor track using the Vicon Nexus 3D motion capture system (Vicon Motion Systems Ltd.) fitted with 44 cameras and 16 Kistler Force Plates. The data were filtered, and ground contact time, power, and work were calculated for the foot. A linear mixed-effects model was used to examine the relationship between age, sex, and velocity on ground contact time, power, and work.
RESULTS:
From the linear mixed-effect model, there was a statistically significant (p<0.001) effect of velocity on ground contact time, power and work. There was a statistically significant (p<0.01) effect of age on ground contact time and maximum power and approached significance (p<0.1) for positive work. There was no statistically significant effect of sex on ground contact time, power or work, however it should be noted that statistical significance was approached (p<0.1) for the effect of sex on negative work.
At slower running velocities (2m/s) the younger adults had a longer ground contact time than the older adults. At a mid-running velocity (4m/s), the younger and older adults had similar ground contact times. At their maximum running velocity, all participants appeared to reach a critical point, however the older adults reached this critical point at a slower velocity compared to that of the younger adults.
For maximum and minimum power, and positive and negative work, the younger adults had more extreme values compared with older adults. The differences between work and power between age groups were more prominent at faster running velocities.
CONCLUSION:
Our results show that the differences in the contributions of the foot due to age were predominantly during the repulsive phase of the foot strike and greater at higher running velocities. It was also found that sex did not have a statistically significant effect on these variables. These findings suggest that the repulsive phase of foot strike in running is affected as we age, which influences our capacity to move.