M.M. O’Hollaren, S.E. Risso, A.E. Zander, A.D. LaGoy, A.L. Johanson, K.M. Bishop, M.S. Fogarty, D.B. Thorp

Department of Human Physiology, Gonzaga University, Spokane, WA

Cognitive tasks predominantly accomplished using the prefrontal cortex are affected by both long duration exercise and blood glucose levels. It is plausible that decreased cognitive functioning observed during long duration exercise could be due to a drop in blood glucose, although this relationship remains to be elucidated. PURPOSE: To determine if prolonged moderate intensity exercise would lead to decreased prefrontal cortex specific cognitive functioning concomitant with a decrease in blood glucose concentration and whether this can be prevented, or at least attenuated, with carbohydrate ingestion throughout exercise. METHODS: Nine active undergraduate students (20.22 ±1.1 yr.) completed two 135 min cycling bouts at an intensity corresponding to 75% of age predicted heart rate (HR) max during which subjects ingested either 2g glucose/kg body weight using a 5.8% carbohydrate beverage (CHO) or an equal volume of placebo beverage (Pl). Each subject performed these conditions in a counterbalanced order. Blood glucose (BG) (measured via capillary blood) and HR were measured every 10 min. Cognitive functioning was assessed using the Stroop test every 30 min, along with rate of perceived exertion (RPE). BG and cognitive functioning were also tested before as well as 15 min post-exercise. All variables were evaluated using a two-way repeated measures ANOVA followed by LSD post hoc tests. RESULTS: BG levels decreased from baseline (5.23±0.5 mM) at 60 minutes and remained decreased until 15 min post exercise (4.05±0.5 mM) in the PL condition (p<0.05); BG did not change from baseline throughout the CHO condition (5.53±1.0 mM). Time to complete the Color-Word Interference Stroop subtest decreased from baseline (36681.45±3662.9 ms) to end of exercise (33145.94±3250.0 ms) in both conditions (p<0.05), indicating an increase in cognitive functioning. CONCLUSION: A decrease in cognitive functioning during exercise was not observed in the current study despite a significant drop in BG during the PL condition. This may be because BG levels did not decrease to 3.3 mM, which has been previously shown to be associated with decreased cognitive functioning. The increase in cognitive functioning seen towards the end of exercise was most likely due to an increased state of arousal.

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