THURSDAY, July 31 (HealthDay News) -- A simple pill, combined with exercise training, might enhance speed and endurance in athletes.

Researchers reporting in the July 31 issue of Cell discovered that young adult mice that exercised and took a drug originally developed to treat metabolic diseases ran considerably farther compared with mice who only exercised. Adding yet another compound increased endurance even more, basically "tricking" the muscle into thinking it was being worked daily.

Even harder than tricking muscles, however, is translating animal findings into benefits for humans.

"It's an animal study, and it's a relatively small sample," said Malachy McHugh, director of research at the Nicholas Institute of Sports Medicine and Athletic Trauma at Lenox Hill Hospital in New York City. "It's very interesting, but putting genetic-type research like this into context is quite difficult at the early stage. It can offer up great potential but, when you then go to humans and when you then go to trained humans, the potential may not be there."

The advantages of exercise are well known: By reducing obesity and keeping body within normal weight, physical activity reduces the risk for cancer, diabetes, heart diseases and a myriad of other diseases.

But getting individuals to actually engage in 30 minutes or 40 minutes of exercise a day is another story.

In 2004, these researchers, from the Salk Institute and the Howard Hughes Medical Institute in La Jolla, Calif., altered the PPAR-delta gene to produce mice with altered muscle composition and increased endurance. These mice were able to run twice as far as their "normal" brethren and also tended not to gain weight, even when eating a fat-heavy diet.

PPAR-delta regulates other genes. By altering its function, researchers basically tilted the scales for muscle cells to burn more fat than sugar.

But this experiment took place in younger, developing mice. In other words, they were "pre-programmed."

Could a drug "reprogram" adult mice?

The researchers gave a drug called GW1516, which increases the activity of PPAR-delta, to young adult mice for five weeks. The result: nothing.

So, they added another element: four weeks of exercise training. The drug combined with the training increased the rodents' running time by 68 percent and distance by 70 percent compared with mice receiving exercise training alone.

The muscles of the mice receiving both the drug and the training also showed evidence of new patterns of gene activity not seen in mice taking the drug alone or exercise training alone. The pattern was similar to the one seen in the earlier, genetically engineered mice.

Adding another compound, AICAR, which affects the activity of an enzyme called AMP kinase (AMPK) not only replenished energy in the cells, but also helped PPAR-delta activate its genetic targets.

The findings, released on the eve of the Beijing Olympics, also have a troubling side: the potential for abuse by athletes.

Aware of this problem, the study authors have already consulted the World Anti-Doping Agency and are also developing a test to detect the use of GW1516.

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