Finding the motivation to exercise is hard enough, but finding the motivation to exercise in December is another thing entirely.

It's pitch dark when you get up, pitch dark when you leave the office, and you have a bed that can't do enough for you, so it's no surprise most of us see our exercise routine fall by the wayside once winter sets in.

But if you've been busy beating yourself up over your desire to spend an extra hour under the covers instead of slogging it out on the treadmill, stop right now because the experts have your back on this one.

According to a study from Chicago's Northwestern University. our muscles work more efficiently when our body is properly awake which means early-morning workouts aren't all they're cracked up to be.

"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," wrote lead 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. In the future, we may discover new ways to manipulate the oxygen response of the cell by resetting the clock."

"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."

So, if you've been trying and failing to hit up the 6am spin class for the last month, don't worry because it sounds like the lie-in would do you better.

Score!