Time to Change It Up?

Tractor tires leave huge ruts in wet fields and I believe I've fallen into one and need to figure out how to get out.  My hard core (as some call it) exercise program has virtually disappeared since I stopped the training for distance running.  I gave myself some time to heal my abused legs and feet and got a little to comfortable laying in the bottom of the rut.  Don't get me wrong, I'm still doing my routine morning core work, walking/riding with Ricky, and an occasional 3-4 mile very slow run, but it definitely falls into the "Same old, same old" category in the Top 5 Worst Exercise Habits.  I've been doing more hiking, walking, riding with Rick which is really cool, but its not getting the heart rate up enough to improve fitness.  Yes, our exercise regimen is the minimum daily requirement of exercise to stay healthy, but not enough to gain a little muscle. What to do?  Should I focus on learning the play moves of play boating? Throwing a play boat around definitely takes some serious energy as I found out this winter in the pool sessions.  I'd be tired in a half hour and start missing rolls.  Or maybe I should go back to my exercise roots of the eighties and start pumping iron again.  Weightlifting is one of the best osteoporosis preventatives, so I can't go wrong doing a couple reps every day.  Then there's my current passion (obsession?), the garden.  I always felt I was getting 3-4 hours of exercise everyday working in the garden.  It turns out, gardening is an activity and I still need to exercise.  If the heart rate doesn't rise, its an activity, not exercise.  Yes, any movement is good, but aerobic exercise is better.  Or maybe I need to find something completely new to really mix it up.  What could that possibly be when I've climbed just about every mountain at this point and have no plans to spend anything on anything new.  I like my friend's comment, "when was the last time you did something for the first time?"  Hmmm... thinking that through a little points me to getting some use out of that play boat.  What did I get if for, anyways?