The ancients who developed Chinese medicine believed that we should live in harmony with the seasons—so in winter we should focus on nurturing yin and subduing yang. It is a time to recuperate and revitalize, especially our Kidney energy (since winter is considered the season of the Kidneys). Canadian mothers were right to tell their children to keep their Kidneys (aka the lower back) warm and covered in the cold, because this helps keep us healthy and well. Especially true for anyone at all prone to aches and tightness in this area. The bones are thought to be associated with the Kidneys, so it also makes sense that moms instinctively put a bone in the soup pot to make nourishing broth to feed their families during the winter months.
So this winter, follow your instinct: Rest more, eat nourishing foods, and keep warm.