I have hiked in years past up to 12,000 ft but normally topped out around 8,000 ft when doing day hikes. Problem is that I'm in my 60's, haven't hiked in 3 years and live at an altitude that tops out below 1,000 ft . I'd liked to feel comfortable enough that I could do a 6 mile round trip day hike topping out at 8,000 ft.
My question is how best to condition myself and get back in shape to do these kind of hikes? Any suggestions would be appreciated.