I'm 76 and am still able to cycle, hike, backpack, ski (both X-country and alpine) and kayak (touring only). I feel pretty good when I do these things, though my recovery time seems longer than it used to be. The physical consequences of being old for me is pain. When I engage in these activities I'm almost always feeling some kind of ache or pain. I've had one knee replacement and one hip replacement. The other knee and hip offer some discomfort, but nothing serious yet. I do get tired faster. I can remember when I used to ski six hours in a day. Not anymore. Three to four is enough. My average bike ride is 20-25 miles whereas twenty years ago it was 30-40. But I'm still healthy and enjoying life, which is my good fortune.