The Effects of Caffeine on Cognitive Performance During and Following Prolonged Exercise to Exhaustion

Caffeine is thought to act as a central stimulant and to have effects on physical and cognitive functioning. However, there currently is no information available describing the effects of caffeine on cognitive performance during endurance exercise. PURPOSE: To examine the effects of ingestion of a cereal bar containing caffeine before and during cycling exercise on physical and cognitive performance. METHODS: 24 well-trained cyclists consumed the supplements (cereal bar containing 45g carbohydrate, 3 g fat, 5 g protein and 4 g fiber with 100 mg caffeine (CAF), isocaloric non caffeine cereal bar (CON), or 300 ml of placebo beverage (BEV)) at rest and performed 2.5 h of exercise at 60%VO2max. Additional supplements were taken after 55 and 115 min of exercise. During exercise measurements of respiratory gas exchange, heart rate, rating of perceived exertion and blood glucose were made every 20 min. Cognitive function measures (computerized Stroop and Rapid Visual Information Processing (RVIP) tests) were performed at rest before exercise and while cycling (70 and 140 min of exercise). At the end of the 2.5 h of exercise subjects were given a 5 min break, immediately followed by a time to exhaustion trial (T2EX) at 75%VO2max. The same physiological and cognitive measurements were applied 5 min after completing the T2EX ride. RESULTS: Participants were significantly faster after CAF when compared with CON on the computerized complex information processing tests (Stroop Colour Word and RVIP), particularly after 140 min and after the T2EX ride (p<0.001). On the BEV trial, performance was significantly slower than after both other treatments (p<0.0001). T2EX was longer after CAF consumption compared with both CON and BEV trials (p< 0.05) and T2EX was longer after CON than after BEV (p< 0.05). No differences were found in the RPE, mean heart rate, and relative exercise intensity (%VO2max; p> 0.05). Blood glucose concentration was lower in the BEV trial compared to both CON and CAF trials. CONCLUSIONS: Caffeine in a cereal bar can significantly improve complex cognitive ability during and after exercise. These effects are particularly strong after exercise to fatigue and may be salient for sports performance in which concentration plays a major role.