Research and Development of an Advanced Personal Load Carriage System Phases 2 and 3. Section D: Development of Acceptance Criteria for Physical Tests of Load Carriage Systems
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Abstract : Standardized physical testing of 1oad carriage systems allows for comparison between load cam age simulator measures, stiffness measures, and human performance measures from field trials. The objectives of this project section were to develop benchmark criteria from a pool of pack measures, and to use the correlation between human and simulator measures to establish threshold limit values (TLVs) for bearer safety. A Pearson correlation matrix with 76 total variables (39 LC simulator variables, 37 stiffness and field testing variables) was developed with a significance level of p=.05 for all correlation values r=0.67. Results showed 11 displacement/force LC simulator variables and 10 pressure/stiffness variables significantly correlated with human factors measurements. Of note, pack displacement was strongly correlated with posterior hip discomfort, indication excess loading of the hip belt. Force and moment averages and amplitudes were correlated with mobility and comfort. Most notable was the high correlation between vertical force amplitude and overall pack ratings in the human trials. Pressure measurements were also significantly corelated with subject discomfort scores, while stiffness about all three axes was associated with mobility and function in human trials. LC simulator variables which showed significant correlation with human trials results were placed m a benchmark pool, where upper and lower limits were established at the 10th and 90th deciles using the mean and standard deviation values for the benchmark pool, as well as the t-distribution estimations. In this way, future pack testing results can be interpreted as superior, inferior, or typical, if they exceed the upper decile, fall below the lower decile, or lie between deciles respectively.