| Abstract | Canada is currently the only country in the world that allows the use of thermal manikins to measure the thermal protective properties of immersion suits. This is advantageous compared to having multiple human participants perform the long cold water immersions necessary for suit testing; however, previous research has shown that differences exist between the two that may cause unexpected results. The goal of this study was to compare the thermoregulatory responses of human participants and thermal manikins during cold water immersions while wearing three different custom made immersion suit ensembles. One ensemble had insulation distributed evenly around the torso and limbs (Control); another had insulation concentrated around the torso (Human Beneficial – HB); and the third had insulation concentrated around the limbs (Manikin Beneficial – MB). Eleven male participants performed three separate, three-hour immersions in 5°C water. Mean skin temperature, skin heat loss, gastro-intestinal temperature, and metabolic heat production (calculated via oxygen consumption) were measured throughout these tests. The thermal manikin also performed immersions in the same conditions to measure the clo value of each ensemble. No significant differences were found across the three immersion ensembles in total mean skin temperature change, total mean skin heat loss, gastro-intestinal temperature change, and metabolic heat production. The total clo values of the three ensembles, as measured by the thermal manikin, were very similar with less than 10% difference between them. When comparisons were made at the regional level (i.e. torso and the limbs) significant differences were detected in the some physiological measurements between the ensembles. The thermal manikin also reported higher regional clo values in the torso in some ensembles compared to others. The initial findings from this set of tests suggest that concentrating insulation around the torso or the limbs of an immersion suit will not affect the level of thermal stress placed upon the humans who wear it, nor will it change the clo value as measured by a thermal manikin. As a result, this may indicate that once a certain amount of insulation is contained within an immersion suit, altering its distribution between the torso and limbs may not impact the level of thermal stress placed on humans, or measured clo values. |
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