Even if you're in great shape, your muscles get tense up more in colder temperatures. Add that to the fact that most people are holed up inside looking at screens or hunched over their computers and you've got a recipe for tight muscles.
Majka recommends taking time to stretch out every day, even if it's just five minutes when you wake up or before you go to bed. Grab a yoga mat and be sure to stretch out all your sore muscles, allowing your body to wake up and wind down.