Could mice teach us about the best time of day to exercise?

Scientists have discovered that muscles can be more or less amenable to exercise depending on the time of day, according to a new report published in the journal Cell Metabolism.

The researchers, from Northwestern Medicine, say that the study shows that muscle cells are more efficient during an organism’s normal waking hours. This is because there are circadian ‘clocks’ in muscle tissue that control the muscle’s metabolic response and energy efficiency.

During the study, which was carried out on mice, the researchers performed muscle biopsies which determined the impact of deregulation of the circadian clock on muscle fibres in terms of how muscle processes fuel, like sugar and fat, when oxygen levels are low. Prior to this the mice were exercised at different times of the day.

When the mice, which are nocturnal, were exercised at night, their muscles were found to be better at turning on genes to help them adapt to exercise. The researchers say that since these genes also exist in humans, we may also be able to respond better to exercise during the daytime.

The study’s senior author, Dr. Joseph Bass, said:

‘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. The capacity for a cell to perform its most important functions, to contract, will vary according to the time of day.’

‘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.’

Instant analysis

This is an interesting idea and it certainly makes sense that we would be adapted to exercise better at certain times of the day, dependent on our natural habits and rhythms as well as nutrition, hormones etc. Unfortunately, as this particular study was carried out on mice, it is difficult to conclude from this data how humans would be affected, or indeed how exactly this information could be applied in real life to result in better performance.

Research score: 1/5

MB