Cooling and rewarming of the hands of military conscripts following a standardized cold challenge

The ability to maintain manual dexterity is important for Armed Forces personnel, as it is for e.g. industrial workers who have to handle tools and equipment outdoors. To increase our knowledge in this field, scientific studies are required in order to help prevent local cold and frost damage with a consequent reduction in dexterity. The object of this report is to contribute to this field of knowledge by examining whether cold weather exposure during military service in northern Norway, including participation in a winter field exercise, affects physiological responses (cooling rate and/or heating rate) in hands. The aim of the analysis was to find out whether it is possible to identify changes in cooling and/or heating rate in the conscripts’ hands after participating in the winter exercise. This report presents results from analysis of a data set consisting of examining skin temperature changes following a standardised cold provocation test on the back of the hands of two cohorts of conscripts in basic military training at Setermoen garrison, of which one cohort started their service in August and the other in January. The temperature data was generated from thermographic images that the Norwegian Armed Forces Joint Medical Services had taken from the hands of the two cohorts of conscripts at two time points; first during the first week of basic training and then following participation in a winter exercise. Analysis of the data set shows a tendency in both cohorts that their hands warm up a little faster following the winter exercise compared to the findings from the first week of basic training. No difference in reheating rate between the two cohorts was found. However, the hands of the August cohort tended to cool down faster after the winter exercise than in the first week of basic training in August. This tendency was not seen in the January cohort. This study was not designed to explain the cause(s) of these findings. In order to better understand whether cold weather exposure, and possibly seasonal acclimatization, affects physiological responses (cooling rate and/or heating rate) in the extremities, there is a need for control of these variables. The importance of this research for the Armed Forces is to investigate whether training under winter conditions reduces a soldier’s ability to rewarm the hands following a standardized cold stress test. Such a finding is indicative of a local cold weather injury, and a reduced operational capability during winter training.