Should I worry about getting less exercise in winter?

As the light levels fall and the temperature drops, is it OK to just hunker down and take it easy till spring? Or will that bring on the blues?Ah, winter. Season of hot toddies, roast dinners, heated blankets and mulled … everything. Much less of an idyllic time for getting up early to hit the gym, going for a run in the evening darkness or even going for a bracing walk at lunchtime. And the evidence confirms what you probably suspect: in the winter, we tend to make our training sessions a bit shorter and spend more time sedentary. So are we casual exercisers doomed to backsliding in the icy months, or are there ways to tackle it? And does anything about the colder, darker months actually make maintaining your fitness easier?First of all: yes, it’s helpful to make the effort during winter, even if you’re not concerned about your six-pack or 10k time. Seasonal affective disorder, which seems to affect women more than men, may affect not just mood but health more generally, though it’s n