Up until about 5 years ago I would get my "trail legs" after one or two hikes that would give me sore muscles afterwards. After those hikes, I seemed to reach a pretty good fitness, even if I hadn't hiked for a while. But then things changed; I had a couple years of lots of desk work, coupled with taking care of aging parents that replaced my gym time (and then some). Then I retired from the desk job and jumped back into a hiking routine, and it just doesn't seem to work the same. Going right back to my same old pattern of hiking 12 mile day hikes as if I were still 20/30/40 yrs old and expecting to be in shape after a few times, instead I got plantar fasciitis and some hip muscle problems that I am still working on a couple of years later (I am 57 now). I am now having to basically start over, doing physical therapy on the ailing parts and gradually increasing my miles.

So I guess I'm saying take it slow and listen to your aches and pains, increasing workouts gradually, and especially if you are over 40!