Dark days and cold nights can hinder motivation when it comes to fitness training, but apparently it just boils down to overcoming our instincts.

The circadian rhythm, says executive fitness trainer Jim Stubbs, is an innate human ability to gauge when we should be tired and when we should be active, and is dependent on two major factors: core temperature and light.

"While clothing and central heating largely enables us to ignore the former problem, it's much harder to deal with the diminishing light during winter," says Mr Stubbs.

"One of the best things we can do to maintain emotional and physiological stability in winter is to take regular exercise," he adds.

Mr Stubbs advises taking vitamin D supplements to boost daily intake - those made with fish oil have the added benefit of keeping joints healthy.

University College London also recently noted that a diet rich in fruit, vegetables and fish may help ward off depressive tendencies.

Also, Mr Stubbs adds, the body favours routine, so anything you can do to stick to a schedule will help.

During winter months, it may help to sign up to a few sporting events, like an indoor rowing contest or 10 km run.