Biomechanical Assessment of Rucksack Shoulder Strap Attachment Location: Effect on Load Distribution to the Torso
QUEEN'S UNIV KINGSTON (ONTARIO) SCHOOLOF PHYSICAL AND HEALTH EDUCATION
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The objective of this study was to conduct biomechanical testing of pack component options to determine the optimal location for the lower attachment of the shoulder strap for the Clothe the Soldier CTS Integrated Patrol Pack and Rucksack. A model of a 50th percentile male torso has been split transversely at T12L1 and instrumented with two six degree of freedom load cells. The shoulder area of the manikin was instrumented with FscanTrademark sensors to record the contact pressure distribution in the axilla armpit and anterior of the shoulder under the shoulder strap. A 25 kg fixed payload was used for all test configurations. Waist belt, load lifter and shoulder strap tensions were constant during testing. Output variables were reaction forces at T12L1, waist belt lifting force, average and peak contact pressures about the shoulder. These were examined as a function of the attachment point location and as a function of the angle the shoulder strap made with respect to the body long axis. Strap angles above 30 degrees resulted in peak axilla contact pressures ranging from 35 to 64 kPa. At strap angles less than 24 degrees, anterior shoulder peak pressures of 32 kPa were recorded. These two effects determined the upper and lower bounds of an optimal range of 24 to 30 degrees with respect to the vertical axis of the body. These results cannot be extrapolated to other attachment locations that were not tested and pertain only to the type of strap tested.
- Anatomy and Physiology
- Stress Physiology