For a busy physiologist at the University of Pennsylvania's Perelman School of Medicine, that may be expected, but the reason behind the calls wasn't exactly run-of-the-mill.

The people on the other end of the line were athletes in search of a particular kind of fix: They wanted him to dope them -- via their genes.

In the late 1990s, Sweeney made headlines because of his research on "Schwarzenegger mice," which were up to 30% stronger than their average counterparts. Sweeney had been able to isolate the gene responsible for activating a protein -- IGF-1 -- that controls muscle growth and repair.

The main focus of his experiments was on how to limit the deterioration of muscles with age, but the results also appealed to athletes in search of a performance boost.

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Word got out, however, that he was not interested.