Salk Institute researchers have found two drugs that mimic or improve the benefits of exercise, boosting endurance in mice by changed metabolic properties of the animal’s muscle.

In earlier research, they genetically engineered “marathon mice”–animals with double the running endurance of normal mice. The superstamina came by boosting expression of the PPAR-delta gene. The new research shows the same changes to PPAR-delta can be triggered by drugs, a development that could potentially make the results applicable to humans.

The AICAR drug enhanced running endurance by 44 percent in four weeks without any training. The other drug, GW1516, was even more effective, but only when combined with exercise. It allowed active mice to run 50 to 75 percent longer, giving them more slow-twitch (endurance) muscle fiber.

If the drugs work the same way in humans, they could help people at risk of diabetes or with muscle-wasting diseases like muscular dystrophy. They could also make regular endurance exercise seem easier to people who don’t exercise.