Researchers say they have found a genetic switch that tells muscle to convert into the slow endurance tissue seen in aerobics, enthusiasts a discovery that could lead to a drug that would stimulate exercise's natural effects. But researchers warn people not to expect a work out by pipping a pill instead of breaking a sweat. The researchers, whose work was published on Thursday in the journal Genes and Development, believe the genetic switch could help create a drug that would help diabetics and heart patients.