Effects of Repeated Caffeine Administration on Voluntary Wheel Running in Mice

Abstract

0144 Caffeine administration can have ergogenic effects on endurance exercise performance during a single bout of maximal forced exercise in both humans and animals. However, little is known about the effects of specific dosing regimens of caffeine on 24-hour voluntary physical activity patterns over multiple days. Purpose: To examine voluntary running patterns over 3 days in male mice in response to 3 consecutive doses of caffeine given at hourly intervals at the beginning of their inactive/sleep period (lights on). Methods: 7–9 week old male CD1 mice (n = 16) took part in 3 treatment conditions involving consumption of highly palatable food pellets (0.5g) containing no caffeine (CON), low dose caffeine (LO; 6mg/kg), or high dose caffeine (HI; 12mg/kg) at 7, 8, and 9 am for 3 days in a repeated measures design. Daily voluntary running patterns were recorded by computer with Vital View data collection/analysis software (Mini-Miter). Results: Repeated measures ANOVA showed no main effect of treatment (caffeine at two doses) on overall 24 hr wheel running (distance, time on wheel, and peak speed). However, there was a significant treatment × time interaction that showed differences between treatments at the beginning of the light period (when caffeine was given) and the subsequent dark period (when mice are most active). Between 7–11am when caffeine was administered, both HI and LO caffeine increased distance, time and peak speed above that of CON. There were no significant differences between HI and LO during this period. Conversely, during the subsequent 4-hr period at the beginning of the dark period there was a greater rebound decrease in distance, time, peak speed for HI compared to LO and CON. Conclusion: Both high and low doses of caffeine showed similar increases in voluntary running behavior when given at hourly intervals during the 1st 3 hours of the inactive/sleep period in mice. However, the lower dose of st caffeine would be recommended because it was without the possible disadvantage of reducing activity during the subsequent peak activity period. Information such as this could be useful when designing nutritional strategies to maximize worker performance in military or industrial settings when frequent changes in work schedule is necessary.