Melatonin and sleep responses to normobaric hypoxia and aerobic physical exercise: A randomized controlled trial

Abstract

This work evaluated the effects of moderate physical exercise performed under hypoxic conditions on melatonin and sleep. Forty healthy men were randomized into four groups: Normoxia (N) (n = 10); Hypoxia (H) (n = 10); Exercise under Normoxia (EN) (n = 10); and Exercise under Hypoxia (EH) (n = 10). The observation period for all groups was approximately 36 h, beginning with a first night devoid of any intervention. Aerobic exercise was performed by the EN and EH groups on a treadmill at 50% of the ventilatory threshold intensity for 60 min. Sleep evaluation was performed on the 1st and 2nd nights. Venous blood samples for the melatonin measurement were obtained on the 1st and 2nd days at 7:30 AM as well as on the 1st and 2nd nights at 10:30 PM. On the 2nd night, melatonin was higher in the H group than in the N group, but both were lower than values of the EH group. The nocturnal increase in melatonin was inversely correlated with the oxygen saturation of hemoglobin (SaO%) on the 2nd night in the H group and on the 2nd day in the EH group. Diurnal remission of nocturnal melatonin appeared to be postponed in the H group and even more so in the EH group. Thus, normobaric hypoxia, which is equivalent to oxygen availability at an altitude of 4500 m, acutely increases melatonin. Moreover, diurnal remission of the nocturnal increase in melatonin seems to be delayed by hypoxia alone but even more so when acting together with exercise.

Carbohydrate and Glutamine Supplementation Attenuates the Increase in Rating of Perceived Exertion during Intense Exercise in Hypoxia Similar to 4200 m

“…Although the participants remained at rest for the two hours preceding exercise, the SpO 2 % at the beginning of the exercise was lower than the expected normoxic values for humans, proving the condition of hypoxia indicated in our study, similarly to other studies [31,32]. SpO 2 % decreased even more after 15 min and remained at a lower level after 30 min of exercise without supplementation.…”

“…The concentration of lactate [44], hemodynamic changes such as changes in HR [45], and SpO 2 % [7,32] could explain the effects of supplementation with carbohydrate and glutamine. However, there was no change in these parameters between the three conditions.…”

Impact of Melatonin on Skeletal Muscle and Exercise

“…However, in previously sedentary men and women aged 40-75 years after one year of moderate exercise, the urinary melatonin metabolite levels were unchanged [175]. Recently, as a result of a moderate exercise in a hypoxic status (equivalent to at 4500 m altitude), serum melatonin increased, probably to protect against oxygen deprivation [176].…”

Exercise-induced oxidative stress and melatonin supplementation: current evidence

“…The studies varied in many respects, as exercise duration (short time-from 1 to 8 days, long-lasting-from 2 to 12 months), exercise type, exercise intensity (moderate, moderate-to-vigorous, acute until exhaustion), training conditions (hypoxic, normoxic conditions, indoor training, outdoor training), sex, and measuring the timing of maximal secretion of MT as well as the measurement methods. An increase of MT concentration following PE in the morning [ 90 ] and in hypoxic conditions [ 91 ], decreases in the same [ 79 , 92 ], and a lack of the effect [ 93 , 94 ] were reported. Referring to the MT measurement timing, Carlson et al [ 90 ] observed that exercise performed in the morning resulted in elevated MT secretion by 20% compared to the hormone secretion induced by the afternoon exercise.…”

“…Two months exercise from 9:30 to 9:55 p.m., two months silent MT measurements: 24 h prior to exercise, 48 h after exercise, two months after the last exercise Significantly decreased MT levels in PBMCs with exercise: post-exercise 7.94 ± 0.35 pg/mL, 2-month silent 6.05 ± 0.27 pg/mL vs pre-exercise (9.16 ± 0.19 pg/mL). Significantly increased IL-17 secretion by 39% in the post-exercise time Long-lasting engaging in moderate-intensity exercise caused decrease in MT release, and increase in IL-17 cytokine level De Aquino Lemos et al 2018 [ 91 ] RCT ( n = 40) healthy men randomized into four groups: normoxia ( n = 10), hypoxia ( n = 10), exercising under normoxia ( n = 10), exercising under hypoxia ( n = 10), (average age 22 ± 3 years). Observation period 36 h Aerobic moderate exercise on a treadmill at 50% of VT1 for 60 min, performed under normoxia and hypoxia conditions from 11:00 a.m. to 12:00 noon blood MT detection: at 7:30 a.m. (the 1st and 2nd days), at 10:30 p.m. (the 1st and 2nd nights) Significantly increased nocturnal blood MT levels in the hypoxia group vs the normoxia group after the second night; both values were lower than those in the exercise group under hypoxia PE under hypoxia enhances nocturnal level of MT, influences its daytime level, and improves sleep quality Carlson et al 2019 [ 90 ] 12 healthy males, regularly exercising, runnerslage (average age 20.7 ± 0.62 years) Three protocols: 30 min of steady state running on a level treadmill at 75% morning exercise (9.00 a.m.), afternoon exercise (4:00 a.m.), no exercise.…”