Im 64 years old, and hadn't ridden a bicycle in MANY years. About 6 weeks ago, I bought a Specialized Crosstrail. Have been taking it easy as I try to get this old body accustomed to riding again. Really enjoying it. Love the way I feel. Am now riding about an hour on each outing, but not high speed. Have stuck to paved streets, with virtually no hills. Thinking it's time to add some hills, and maybe try some mountain trails. Want to minimize the chances of injury from overdoing it.

I'd appreciate any suggestions based on your experience... How many days/week? Is it safer to give my body more time on flat terrain before pushing it on hills?