Prolonged Sleep Deprivation and Continuous Exercise: Effects on Melatonin, Tympanic Temperature, and Cognitive Function

The purpose of this study was to examine tympanic temperature, melatonin, and cognitive function during a 36-hour endurance event. Nine male and three female participants took part in a 36-hour sustained endurance event without sleep (N = 12, mean age = 31.8 ± 5.0 yrs). Participants were stopped for data collection at checkpoints throughout the 36-hour event. Tympanic temperature was assessed, a psychomotor vigilance test (PVT) was administered, and saliva samples were collected. Salivary melatonin was determined via immunoassay. During the 36 hours of competition, melatonin levels were negatively correlated with the day of the race (rs = −0.277, P = 0.039) and positively associated with nighttime (rs = 0.316, P = 0.021). Significant main effects of tympanic temperature (P < 0.001), day of the competition (P = 0.018), and a tympanic temperature ∗ day of competition interaction (P < 0.001) were used to predict minor lapses in attention. No associations between melatonin levels and cognitive function were observed (P > 0.05). During the event tympanic temperature declined and was associated with an increase in lapses in attention. With sustained endurance events becoming more popular future research is warranted to evaluate the physiological impact of participation.