Identification of the relative motion between a torso and backpack with different loads

Abstract

This research is part of a larger study at Queen’s University to create load-bearing guidelines for the Canadian Forces and to examine the biomechanical effects of carrying heavy loads for long durations. The specific objective is to identify the relative movement between a backpack and a body using a load carriage simulator (LCS) in which a mannequin is driven by computer controlled pneumatic activators to simulate the vertical displacement pattern of walking. Relative motion and forward lean angle were measured using an accelerometer mounted on the upper chest of the mannequin and an accelerometer mounted inside a backpack placed on the mannequin. The backpack was packed with four different loads – 16.6 kg, 25.9 kg, 38.7 kg and 50 kg. It was found that the mannequin forward lean angle increases with increasing load but there is no distinctive trend in the pack angle. The mean relative differences vary across the four loads, indicating that the relative movement between the torso and pack varies with load. In general, the mean relative differences in the vertical accelerations between the torso and the pack increase with load – however the results for the 25.9 kg load are anomalous. The power spectral densities of the acceleration signals from the four loads also showed distinctive patterns.