Is the post-lunch dip in sprinting performance associated with the timing of food ingestion?

Abstract

To detect whether the drop in performance around lunch has any direct association with the time of food ingestion, a group of 8 sprinters were studied for 5 consecutive Saturdays. On each testing day, the times achieved during 80 meter sprints performed at eight different times of the day separated by 2 hour intervals were recorded. The 1st and 4th testing days, had identical sleep and mealtime schedules, and were therefore considered "control days", while on the 2nd and 3rd testing days the schedule was brought forward ("advanced") or backward ("delayed") by 2 hours respectively. On the 5th testing day the sleep-wake cycle was brought forward 2 hours without changing the mealtime schedule. A post-lunch dip (PLD) was detected on all testing days although at different times. No significant differences in performance were observed between days 1 and 4 while there were differences in performance during the other testing days. It is worth pointing out that PLD occurred at about 15:00 h on the control days, with significant differences between the 2nd (p < 0.05) and 3rd days (p < 0.05), and with the deterioration in performance starting at 15:00 h on the 3rd day despite the fact that lunch had been served at 16:00 h. In conclusion, PLD does not appear to be directly linked to the time of lunch, although lunch itself could potentiate its effects. It is also worth mentioning the fact that this deteriorating effect does not occur after any other meals of the day.