Individual and Combined Effects of Dehydration, Hyperthermia, and Fatigue on Movement Patterns and Cognition Rachel M. Karslo, University of Connecticut Purpose: The purpose of the study was to examine the individual and combined of effects of dehydration, hyperthermia, and fatigue on movement patterns and cognition. Secondly, we wanted to see if the effects of dehydration, hyperthermia, and fatigue lead to a combined increase in injury risk. Methods: 12 males completed a within-subject repeated measures design to study the effects of hyperthermia, dehydration and fatigue on movement and cognition. Subjects completed 4 randomized test sessions in different conditions: hydrated normothermic, dehydrated normothermic, hydrated hyperthermic, and dehydrated hyperthermic. Movement and cognitive testing were performed three times during each test session: pre-exercise, post-exercise, and after a 60 minute recovery session (in which water perfused suits were worn to maintain body temperature). Subjects completed a 90 minute exercise protocol walking on a treadmill (5% incline, 3-4.0 mph) with a 50 lb. military backpack on. The Landing Error Scoring System (LESS) was used to assess movement patterns, and the psychomotor vigilance test and profile of mood state (POMS) was used to assess cognitive function. Results: Rectal temperature, heart rate, and RPE increased from the beginning to the end of exercise, and decreased during the recovery session. The dehydrated hyperthermic condition resulted in higher LESS scores compared to the other three conditions. We observed a significant difference between condition for the change from pos-test to pre-test score (F(3, 33)=6.17, p = 0.002). We observed no significant difference between condition for the change from post-test to recovery-test score (F(3, 33)=2.70, p = 0.06). We observed a significant difference between condition for the change from recovery-test to pre-test score ( F(3, 33)=7.28, p = 0.001). We observed a significant main effect for time with the psychomotor vigilance testing. The time of testing produced a significant effect, including an increase in mean reaction time during post testing (p= 0.13). No difference was found with number of errors or non valid responses (p>0.05). Significant changes for POMS from pre to post testing included: total mood disorder (F(3,33)=13.38, p<0.001), dejection-depression (F(3,33)=5.32, p=0.004), vigor-activity (F(1.63,17.93)=2.95, p=0.09), fatigue (F(1.49,16.40)= 7.52, p=0.008), and confusion-bewilderment (F(3,33)=8.22, p<0.001).. Significant changes were also found for POMS from pre to recovery testing included: total mood disorder (F(3,33)=5.28, p=0.004), fatigue (F(3,33)=11.26, p<0.001), and confusion-bewilderment (F(2.07,22.77)=2.94, p=0.07). Conclusions: We found that dehydration and hyperthermia combined can cause a significant increase in LESS scores. The hyperthermic, dehydrated and fatiguing trial demonstrated the highest average LESS scores. We can conclude that an individual may be at a higher risk for injury when they are dehydrated, hyperthermic, and fatigued. We also found an increase in reaction time during post testing and changes in several mood states. Most significant changes were also in the dehydrated-hyperthermic condition. Decreases in cognitive testing may be the cause of increased LESS scores during this condition.
