A new study by Chicago's Northwestern University claims that the best time to exercise might be during the day when you are most awake.
The paper, published in scientific journal Cell Metabolism on Thursday (Oct 20), says that muscles operate according to their own circadian rhythm.
This means that the body responds differently to exercise at different times of the day - depending on when the day is bright and dark.
It concludes that muscles are most efficient when you are most awake.
"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 synchronized," said senior author Professor Dr Joseph Bass in a statement.
"The capacity for a cell to perform its most important functions, to contract, will vary according to the time of day," he added.
News on the study was carried in several newspapers including The Independent and The Daily Mail.
"We're not saying we can tell athletes when they should work out but in the future, perhaps, you may be able to take advantage of these insights to optimise muscle function," he said.
Dr Bass also shared that the body's internal clock can be altered with drugs, and when they switched off the "clock" in the muscle cells this inhibited exercise from inducing sugar consumption and generating lactic acid.
He said the results of the study could have far-reaching effects beyond exercise, according to The Independent.
"In the future, we may discover new ways to manipulate the oxygen response of the cell by resetting the clock," he said.
"It's also a critical step in understanding how to impact glucose metabolism in diabetes."
This is because diabetes is fundamentally due to the failure of muscle to consume glucose which affects blood sugar levels, a report in The Daily Mail said.
Therefore, strengthening the muscle clock might be an innovative way in eliminating extra glucose to treat diabetes.