Table 1 The effect of physical exercise on melatonin levels in humans

Thrift et al. 2014 [93]

RCT (51 men, 49 women and 51 men and 51 women as a stretching control (average age 40–75 years, previously sedentary)

12-month program of moderate-to-vigorous exercise (60 min daily, 6 days/week at 60–80% \(V{\text{O}}_{2}^{\max }\))

MT detection: baseline and 12-month follow-up urinary metabolite of MT, 6-sulphatoxymelatonin

No statistically significant changed concentrations of 6-sulphatoxymelatonin after 12-months exercises vs controls (p = 0.66). Baseline metabolite levels were significantly higher in women compared to men, but not after exercise

Moderate-to-vigorous 12-month exercise did not change level of 6-sulphatoxymelatonin

Kilic et al. 2016 [94]

Ten healthy, sedentary males (average age 22.2 ± 0.24 years)

Strenuous exercise as acute exercise until exhaustion, according to the Bruce protocol (Cosmed T150 treadmill test). Blood MT detection at rest, at 10:00 a.m. and immediately after exercise as well as after 48 h at 12.00 p.m. (rest) and immediately after exercise

No statistically significant change in serum MT levels after exercise performed during day or night vs the levels at rest: (3.63 ± 0.08 vs 3.37 ± 0.18 and 4.41 ± 0.26 vs 4.33 ± 0.21, pg/mL, respectively)

Exhaustion PE did not affect the level of MT in the blood, independently on exercise timing (daytime, at night)

Zarei et al. 2016 [92]

Thirteen healthy, non-athletic males (average age 19–23 years)

20 min daily of moderate-intensity exercise (running, 50–60% \(V{\text{O}}_{2}^{\max }\)). 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% \(V{\text{O}}_{2}^{\max }\) morning exercise (9.00 a.m.), afternoon exercise (4:00 a.m.), no exercise. Salivary MT detection: 8:00 p.m., 10:00 p.m., 3:00 a.m. following exercise

Significantly increased levels of MT at 03:00 a.m. compared with those at 8:00 and 10:00 p.m. after completed all the protocol session. MT level at 10.00 p.m. was significantly, elevated (by 20%) after morning exercise vs afternoon exercise

Exercising in the morning may increase MT release compared with exercise performed at afternoon

O’Donnell et al. 2019 [79]

Ten elite female netball athletes (average age 23 ± 6 years)

Athletes one netball training session over a 7-day period and one rest day (control). Mean heart rate during training—145 ± 10 bpm, mean rating of perceived exertion—14 ± 1 according to the Borg scale

MT detection: immediately pre-training, 7:15 p.m. and post-training 10:00 p.m. and during control day

Significantly decreased salivary MT levels in pre-training (6.2 pg/mL) and post-training (17.6 pg/mL) vs a rest day (14.8 and 24.3 pg/mL), respectively)

Training caused significantly decreased levels of MT