Muscles work better during the day

Take advantage of your muscles’ circadian clock.

New research has found that cells in the body, including muscle cells, have an internal clock that regulates how they adapt to changes across a 24-hour period. It turns out muscle cells are more efficient during the day time.

Scientists at Chicago’s Northwestern University investigated whether there is a difference between the muscles’ metabolic response and energy efficiency at night compared to during the day.

Tests found that, during the day, mice had a limited ability to utilise oxygen for energy. This is believed to be because an organism would more likely take advantage of their energy stores during their genetically programmed awake hours. Being nocturnal, the mice were exercised at night, and researchers found their muscles were better at switching on the genes that help them adapt to the exercise.

Since similar genes exist in humans, the research has implications for helping our muscles respond better to exercise by working out during the day time.

“Oxygen and the internal clock are doing a dance together inside muscle cells to produce energy, and the time of day determines how well that dance is synchronised,” said senior author Dr. Joseph Bass. “The capacity for a cell to perform its most important functions, to contract, will vary according to the time of day.”

It’s still too early to say how this might affect workout advice, but the results, published in Cell Metabolism, are interesting.

“We’re not saying we can tell athletes when they should work out,” Bass said, “but in the future, perhaps, you may be able to take advantage of these insights to optimise muscle function.”

More importantly than workout advice is the benefit this research might have to general health. Oxygen response is important in all cells, not just the ones in muscles. This research could potentially be beneficial in preventing cancer and heart attacks, both of which can be brought on by the depletion of oxygen in cells.


Peek, C.B., et al. (2016.) ‘Circadian Clock Interaction with HIF1α Mediates Oxygenic Metabolism and Anaerobic Glycolysis in Skeletal Muscle.’ Cell Metabolism October ’16.

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