Abstract
Melatonin is a hormone associated with sleep/wake cycles in humans. The response of melatonin to sleep deprivation is well documented in the literature. However, the effects of sustained exercise and sleep deprivation on melatonin are unclear.
PURPOSE: The purpose of this study was to examine the effects of 36 hours of sustained exercise without sleep on melatonin.
METHODS: 9 male and 3 female participants took part in a 36 hour sustained endurance event without sleep (N = 12, Mean age = 31.8 ± 5.0 yrs). The participants completed a Leisure Physical Activity Survey prior to the event (Total Aerobic Exercise Score = 7.1 ± .1.8, Mean Total Weightlifting Score = 6.7 ± 1.9) with results suggesting high levels of physical activity. Participants were stopped for data collection at checkpoints throughout the 36-hour event. Saliva samples (passive drool) were collected and immediately frozen. These samples were later analyzed with a commercially available EIA kit (Salimetrics, PA.)
RESULTS: During the 36 hours of competition Melatonin levels were negatively correlated with the day of the race (rs= -0.277, p=0.039; Day 1: 46.8±21.9 pg/ml, Day 2: 29.3±14.5 pg/ml, Day 3: 30.8±12.6 pg/ml) and positively associated with nighttime (rs=0.316, p=0.021; Night: 40.5±16.8 pg/ml, Day: 24.2±14.1 pg/ml).
CONCLUSIONS: These data suggest that as the endurance event ensued, there was a trend for declining Melatonin hormone levels. However, even in a 36 hours event without rest, Melatonin levels still remained higher during the dark hours of the day. Research is needed to elucidate other effects that Melatonin may in conjunction with exercise performance with or without sleep deprivation.