The New York Times published an interesting story about Robert Marchand, a 105 year old cyclist who holds the one-hour distance record for cyclists 100 and older.
Scientists studying him found he was able to significantly add to his aerobic fitness late in life. He only began exercising after his retirement. Not only did he get in good shape by cycling most days of the week at a relatively leisurely pace, but at 103, by following a program devised by exercise specialists, which involved riding at high intensity for 20% of the time, he was able to improve his aerobic capacity to the level of a 50-year-old, and improve his pedaling power by 40%.
An inspiring example of how it is never too late to get serious about exercise!