Working out in the winter

So during the summer I will either run two miles or ride my bike 5 miles in the morning before work....but now in the winter it's hard to do either of those things, so I am restricted to sit ups, and stretches on a mat in the house.

Working on cars is often a great physical activity too but again, unless you have a lot of time, big garage and huge heater........It's tough


What do you guys do to stay fit in the winter?
My exercise involves a chainsaw and splitting maul