Physical Stress in the Middle of the Dark Phase Does Not Affect Light-Depressed Plasma Melatonin Levels in Humans

Abstract

The human pineal gland has been shown to be unresponsive to stress-induced sympathetic activation during the day. However, the effects of stress on human melatonin production have received little investigation at night, when the pinealocytes should be physiologically responsive to noradrenergic stimulation. For this purpose, plasma melatonin and cortisol levels were measured in 7 healthy men (aged 25–34 years), both in resting condition and before and after a physical exercise performed between 23.40 and 24.00 h, 30 min after exposure to bright light (2,500 lx). The exercise consisted in bicycling on a bicycle ergometer at 50% of the personal maximum work capacity (MWC) for 10 min, followed by another 10 min of bicycling at 80% of the MWC. The results clearly showed that physical exercise does not affect light-depressed plasma melatonin levels, whereas it clearly increased plasma cortisol concentrations (p < 0.002, two-way ANOVA with repeated measures), systolic blood pressure, pulse pressure and heart rate. These findings suggest that the human pineal gland is not responsive to systemic sympathetic activation induced by physical stress even in the middle of the dark phase.

Effect of nocturnal melatonin ingestion on short-term anaerobic performance in soccer players

“…A standardized light meal was given to each participant at 3 h before starting the tests. Subjects were also maintained in standard conditions throughout the tests: light intensity in the laboratory was about 30 lux, to exclude effects of light exposure on endogenous melatonin secretion (Monteleone et al 1992); ambient temperature was 23 ± 0.6°C and relative humidity was 48 ± 7%. For 24 h prior to each trial, participants were required to abstain from intakes of alcohol and non-steroidal anti-inflammatory drugs; they were also asked not to participate in any strenuous exercise for at least two days prior to each trial.…”

“…In contrast, Reilly et al (2007) showed that mental performance tended to peak around noon, and various studies have investigated the effects of nocturnal exercise on the different components of sleep. For example, Monteleone et al (1992) showed that physical exercise at night blocks the nocturnal increase of melatonin and increases plasma cortisol levels in healthy subjects.…”

“…One of the reasons to conduct the present investigation was the fact that previous data had shown that physical stress at night blocked the nocturnal surge of plasma melatonin, whereas it induced a clear-cut increase in plasma cortisol levels (Monteleone et al 1992). These hormonal effects are temporally related, the cortisol increase occurs immediately before the drop in melatonin.…”

Physical Inactivity of Murine Retrovirus Infected C57BL/6 Mice is Prevented by Melatonin and Dehydroepiandrosterone

“…However, MLT consumption increased average speed, ambulatory time, and distance traveled in retrovirally infected, young mice in comparison to uninfected controls. Exercise can elevate (26) or decrease MLT levels (27)(28). MLT supplementation enhances immunity in AIDS and retroviral infection (29,25) although exercise can elevate (26) or decrease MLT levels (27)(28).…”

Juvenile idiopathic arthritis and physical activity: Possible inflammatory and immune modulation and tracks for interventions in young populations

“…Various studies report that melatonin levels decrease, increase or remain unaffected by physical activity [44][45][46][47][48][49][50]. This variability in melatonin response to exercise can be explained by time of day, light conditions, type, duration or intensity of exercise, and by melatonin sampling scheme.…”