Tina Vindum's Outdoor Fitness as a way to motivate and encourage you to get in shape while enjoying the outdoors. It's a great combination, outdoors and good health. The two are natural partners.
There's even a blog page with a list of topics for your specific concerns and interests. The blog's Goal Setting topic might be a good place to land as we move into the New Year.
If you are an Adventure and Retreat Leader who wants to add a fitness component to your offerings, there is a ton of good information here. The site will jumpstart more than a few good ideas for you.
If you are an Adventure and Retreat Leader who wants to get in shape for your own offerings, better able to keep up with the pack and offer more activities, Outdoor Fitness will help you get started.