Abstract:
Military personnel (Warfighters) are frequently exposed to heavy load carriage as a result
of their job, with all personnel carrying at least 31kg (68.2lbs) of equipment as a standard
fighting load. Carrying posteriorly-based heavy loads like these will cause changes to joint
mechanics while walking to compensate for the additional weight. While trained Warfighters
may have adapted mechanisms to properly compensate for these changes, incoming recruits may
react differently, potentially increasing their risk for injury. This study observed the static and
dynamic postural stability and joint mechanics of persons untrained in load carriage before and
after a simulated ruck march. The simulated ruck march consisted of 20 minutes of walking at
1.34m/s while wearing a 25kg rucksack on the back. Postural stability was assessed before and
after the march, and joint mechanics were assessed before and after the march, as well as in
loaded compared to unloaded conditions. Researchers observed that neither static nor dynamic
postural stability was affected by the simulated ruck march. Stride length decreased and cadence
increased, both as a result of load (p=.035; p=.049, respectively). Left and right hip angles were
more extended at heel strike (p=.004; p=.007) and toe off (p=.008; p=.009) while loaded
compared to unloaded, left and right knees were more flexed at heel strike while loaded (p=.003;
p=.042), and left ankle angles were more dorsiflexed at heel strike while loaded (p=.044).
Participants underwent significantly more trunk flexion while loaded compared to being
unloaded (p<.001). Vertical ground reaction forces were higher as a result of the march
compared to pre-march (p=.013). This data suggests that persons with no load carriage
experience prefer a shorter stride length to compensate for the load, but still observe higher
ground reaction forces.
