Marilyn Graham was 56 when she signed up for a grueling hour of cycling each morning for 12 weeks, occasionally decked out in a mask, a heart monitor and a bag of intravenous fluid and subjected to needle pricks to obtain blood samples. "I was probably the biggest whiner of the group, complaining loudly about the seats and how my butt hurt," said Graham, who writes software for business units on the University of California, Berkeley campus.