Go Ask Alice! is the health question and answer Internet service produced by Alice!, Columbia University's Health Promotion Program — a division of Health Services at Columbia.
Everything depends on your level of fitness. Lance Armstrong said running a marathon was the hardest thing he ever did, I'm just happy to finish one. His sub 3 hour marathon equate to my 1/2 marathon time give or take some minutes.
The quest to develop a stunningly fit, lean and attractive body is a long, slow journey. It's not something you achieve overnight by popping a few pills or strapping an electric gizmo to your belly.