Human load carriage: the ergonomic assessment and development of military load carriage systems

There were two main aims to the thesis: (1) to develop a mobile 'in-field' pressure measurement system to assess pressure at Body-Load Carriage System (LCS) interfaces (shoulders and hips). (2) To evaluate and compare prototype LCS designs in-field and to provide human factor requirements for design improvement. To satisfy the aims of the thesis in-field trials were carried out in a realistic military context. The purposes of these trials were to: (1) compare the standard issue British military LCS against a prototype LCS design in terms of pressure and subjective comfort; (2) increase the understanding of the properties of the shoulder and hip interfaces; (3) assess the relationship between loading at the shoulder and hip; and (4) identify whether other ergonomic issues are also important to consider. By assessing these areas human factors requirements for design were then determined. An additional (minor) aim was to develop a new prototype LCS with a greater degree of compatibility between the components of a military LCS (backpack and webbing), incorporation of material advances, and with a greater consideration for fit and posture. Four main experimental trials were performed the first (n = 11) assessedth e affect of clothing layers at the body-LCS interface on transmitted pressure. Results showed that clothing layers even worn in multiple have no effect on pressure transmission. Thus, no relief from pressure exists for the user. This highlighted the importance of the materials in the shoulder and hip straps. The second trial (n = 10) was a laboratory based comparison of two backpacks, the first the standard issue British military pack, the second a new prototype. Results found significant difference in subjective comfort and also peak pressure at the shoulder interface. The prototype backpack being associated with reduced peak pressure and increased comfort. The third trial (n = 10) assessed whole LCSs (backpack + webbing) in field with civilian participants. The standard issue LCS was compared against a prototype LCS. No significant difference in pressure was identified between the two LCSs, although differences in subjective comfort ratings were still significant indicating a preference for the prototype LCS. The final trial (n = 30) was military in-field trial. Military personnel and loadings were utilised. Again no significant difference in pressure data was identified although differences in subjective ratings remained significant with the prototype LCS design being preferred. Research findings highlighted the continued need for subjective assessment. The relationship between pressure loading at the shoulder and hip interfaces, along with locations of peak pressure within each interface were found to be important factors affecting comfort. Increased pressure distribution at the interfaces via new materials and design was also associated with increased comfort. Other areas which appeared important were the effect of posture and other physical forces not measured (i.e. shear and friction). Human factors guidelines were created for finiher LCS designs and future research ideas were presented.