Physical and cognitive performance during long-term cold weather operations

Background: Physiological responses, physical performance, and cognitive performance were measured during military cold weather survival courses to determine the effects of long-term cold exposure on training safety and potential survival ability. Methods: There were 28 males, from 5 9--d winter survival courses, who participated. Cognitive performance was evaluated through logical reasoning, planning, and vigilance. Physical performance was evaluated with tests of hand function and arm strength. Subjective cold sensation scale (CSS), rating of perceived exertion (APE), and mood indicators were quantified. Core temperature (Tcore) and HR were recorded continuously throughout the courses, and fingertip temperature (Tfinger) was also recorded during testing. Hematocrit values to indicate hydration status were obtained from blood samples taken on three occasions. Results: Mean air temperature (Tair) during the testing periods ranged from -24.4 to 4.4 degrees C among the five courses. Hydration level and Tcore remained normal throughout all courses while Tfinger decreased with decreasing Tair. Finger dexterity deteriorated by 23-28% when Tfinger decreased from 18 to 10 C. Muscular strength was decreased by a small (4%) but significant amount over 6 d of testing. Cognitive function was unaffected by cold air or time on the course. Mood indicators were consistent with CSS and RPE scores. Conclusion: Under the exposure conditions and availability of basic survival equipment, including water, described herein, and in the absence of trauma, healthy fit individuals can participate in this military training without any serious decrements in cognitive and physical performance. In an actual survival situation, similarly decreased dexterity may adversely affect survival activities.