HRV & Sleep

Morning and evening physical exercise differentially regulate the autonomic nervous system during nocturnal sleep in humans

How does my exercise affect my sleep??

The study investigated whether physical exercise in the morning and in the evening regulates the autonomic nervous system differently in humans during nighttime sleep.
The results show that workouts in the morning and in the evening have different effects on body temperature at night and on cardiac activity during sleep. Morning activities improve the quality of nighttime sleep by increasing parasympathetic activity, while avoiding intense evening sessions. This answered the question of what time of day physical activity should be performed for better sleep.

The relationship between daily exercise and circadian rhythm

The effects of daily morning or evening exercise on the circadian rhythm of plasma melatonin and body temperature in healthy young men who stayed in an experimental facility for 7 days in low light (10 lux) were studied. Polysomnogram (PSG) and heart rate variability (HRV) were also measured. The subjects performed 2-hour intermittent physical exercise on four consecutive days with a bicycle ergometer 3 or 10 hours after waking up. The evening melatonin increase was delayed by 1.1 hours on days without training. Polysomnography showed no changes from morning exercise. The deep sleep stages 1 and 2 showed up significantly without training by 13.0%, whereas the dream sleep with training by 10.5%. The nightly decline in rectal temperature was mitigated by evening exercise, but not by morning exercise. HRV changed differently during sleep. Very low frequency (VLF) waves increased without training. VLF, LF, and HR increased after morning workout, while HR increased after evening workout. Morning exercise increased the parasympathetic activity, as indicated by HRV, while evening exercise increased the sympathetic activity, also recognizable by an increase in heart rate during the subsequent nightly sleep. These results showed different effects of morning and evening exercise on circadian melatonin rhythm, PSG, and HRV.

Picture. 1: Heart rate variability during the sleep period. The mean performances of HRVs [very low frequency (VLF), low frequency (LF), high frequency (HF) and LF / HF] during the sleep period are plotted in the control (n 7), the morning exercise (n) 7) and the evening exercise groups (n 8) on Pre-Ex2 (gray) and day 5 (black) (A). Differences in HRVs between Pre-Ex2 and Day 5 were recorded in the control groups (CTL; ​​white, n 7), morning exercise (ME; gray, n 7), and evening exercise (EE; black, n 8) (B)). Asterisks indicate a significant difference (* P 0.05, ** P 0.01, one-sample test).

Conclusio:

In summary, it can be said that daily, moderate physical training has different effects on the circadian melatonin rhythm, the rectal temperature during nighttime sleep, the sleep stages and the HRV, depending on the time of exercise.
Morning exercise increases LF and HR during nighttime sleep, while evening exercise shifts the offset phase of the nocturnal increase in melatonin. Furthermore, the nocturnal drop in rectal temperature is suppressed and the heart rate increased during sleep. Exercising in the morning can improve parasympathetic activity during the following night’s sleep, while exercising in the evening can increase sympathetic activity during the following sleep.

Source:
Yamanaka Y, Hashimoto S, Takasu NN, Tanahashi Y, Nishide S,Honma S, Honma K. Morning and evening physical exercise differentiallyregulate the autonomic nervous system during nocturnal sleep in humans. AmJ Physiol Regul Integr Comp Physiol309: R1112–R1121, 2015. Firstpublished September 2, 2015; doi:10.1152/ajpregu.00127.2015. https://journals.physiology.org/doi/pdf/10.1152/ajpregu.00127.2015

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