Two studies published in the journal Cell Metabolism confirm the impact of our sleep pattern on our performance during physical exertion.
“It is well known that almost all aspects of our physiology and metabolism are dictated by the circadian clock. This is true not only in humans, but also in all light-sensitive organisms. So we wondered if there is a link between the time of day and exercise performance“says Gad Asher of the Department of Biomolecular Sciences at the Weizmann Institute of Science (Rehovot, Israel), co-author of the research.
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Variable oxygen levels depending on the time of day
Led by Paolo Sassone-Corsi of the Center for Epigenetics and Metabolism at the University of California, (Irvine, USA), the first study put mice on treadmills to observe the mechanism of processes like glycolysis ( sugar metabolism and energy production) and lipid oxidation (fat burning).
American scientists have notably discovered that the protein HIF-1α, known to stimulate certain genes depending on the tissue oxygen content, is activated by exercise in different ways depending on the time of day. “Until now, we didn’t know that its levels fluctuated depending on the time of day,“specifies Sassone-Corsi.
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Are you morning or evening?
The second study led by Professor Asher also involved putting mice on a treadmill at different times of the day. They then asked 12 humans to do a similar exercise. Experience has shown that oxygen levels were lower in mice and participants who exercised in the evening compared to those who practiced in the morning, reflecting better efficiency as well as a feeling of reduced effort.
The researchers behind these two studies believe that transposing these results directly to humans would not be convincing since our biological rhythm turns out to be different from that of laboratory mice.
“You can be in the morning or in the evening. These criteria must be taken into account,” says Professor Sassone-Corsi.
The ideal time of the day for physical activity seems to depend above all on our own internal clock and can therefore vary between individuals.
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