To get an aerobic workout and see the woods from a different perspective, try Cross-Country Skiing.
Cross-Country skiing, aka Nordic Skiing, is a sport that takes coordination and stamina. Don't let that scare you; you can develop both and find that your winter outdoor experience goes way beyond what you'd encounter on a normal hike. The trick to it is learning to push off and glide along the snow, making long strides to cover a lot of distance in a relatively short time. If you really work at it, you will develop a solid technique on your own, but a lesson from someone who is experienced will help at first. The skis, boots and poles are different from those used in downhill (alpine) skiing. Skis are long and thin with a texture underneath to help grip the snow. The boots are flexible and ankle-high or slightly higher. The poles are long and have a large bail at the bottom. You don't need to spend a fortune for this equipment, but you might want to rent a few times before buying.