SAN FRANCISCO--Although AIDS patients have been told to avoid strenuous exercise, results of a study announced here yesterday at the Experimental Biology '98 meeting show that they can undertake a major workout without boosting their HIV viral count. Exercise could even help build up the body of an AIDS patient and combat the disabling loss of muscle that afflicts 10% of Americans with AIDS and nearly half of Africans with the disease.
In the past, most doctors warned AIDS patients to refrain from strength training. When sedentary people first begin a strenuous exercise program, tiny rips in their muscles stimulate the immune system. Test-tube experiments have shown that stimulating HIV-infected immune cells with molecules called cytokines helps the virus reproduce and infect more cells. "The worry was that if exercise increases cytokine production, it could actually make people sicker," says Ronenn Roubenoff, an exercise physiologist at Tufts University in Boston.
To check these assumptions, Roubenoff and his colleagues tested the viral loads in 25 AIDS patients taken from a larger exercise study. The volunteers were asked to exercise vigorously--stepping up onto a chair and back down every second for 15 minutes. Afterward, and over the course of the next week, the researchers monitored the patients' viral loads. None of the patients showed an increase in viral load, even though other tests showed increased levels of certain cytokines.
Roubenoff says that the body's immune response probably has some checks and balances that prevent excess viral replication when muscles are strengthened. "It appears that exercise is safe," he says. The researchers plan to release a long-term study of exercise and AIDS patients in June.
Despite the good news, at least one researcher suggests the data should be interpreted cautiously. "I think it's an encouraging finding, but I don't think this one particular study should reverse our advice to AIDS patients on exercise," says Arthur LaPerriere of the University of Miami, in Florida. He notes that many other studies have shown that strenuous exercise can compromise the immune system in other ways, such as by decreasing the number of "natural killer" immune cells, which can help to ward off new viral infections.