Caffeine use in a Super Rugby game and its relationship to post-game sleep

Objective: To examine the relationship between regular game-related caffeine consumption on sleep after an evening Super Rugby game. Methods: Twenty elite rugby union players wore a wrist-activity monitor to measure sleep for three days before, three days after and on the night of an evening Super Rugby game (19:00-21:00). Players ingested caffeine as they would normally (i.e. before and sometimes during a game) and saliva samples were collected before (17:00) and after (21:30) the game for caffeine concentration. Results: Compared to the nights leading up to the game, on the night of the game, players went to bed 3h later (23:08 +/- 66min vs 02:11 +/- 114min; p<.001) and had 1:30hh:mm less sleep (5:54 +/- 2:59 vs 8:02 +/- 1:24 hh:mm; p<.05) and four players did not sleep after the game. Post-game caffeine saliva concentrations were greater than pre-game levels in 17 players (Pre-game 0.40 mu g/mL vs Post-game 2.77 mu g/mL; p<.001). The increase in caffeine saliva concentrations was moderately associated with an increase in sleep latency (p<.05), a decrease in sleep efficiency (p<.05), and a trend for a decrease in sleep duration (p=.06) on game night. Conclusion: Caffeine consumption before a Super Rugby game markedly increases post-game saliva caffeine levels. This may contribute to the observed 3.5h delay in time at sleep onset and the 1.5h reduction in sleep duration on the night of the game. This study highlights the need for a strategic approach to the use of caffeine within a Super Rugby team considering the potential effect on post-game sleep.