Exercise is important for HIV-positive people, but what type of exercise to use is still under debate in the scientific community. Scientific studies found that aerobic exercise increases CD4 counts. Scientists recommend aerobics at any stage of HIV infection. Start at an easy intensity level and do not disrupt the routine; stopping can suppress the immune system. Intensive exercise can also be immunosuppressive. Some cases of AIDS-wasting syndrome have been reversed using weight training and vitamins, antioxidants, or anabolic steroids. Some trainers believe that all cases of wasting can be reversed by this regime, as long as diarrhea is controlled and fever is not present. Aerobic exercise can actually be detrimental to HIV-positive patients because it increases the stress hormone, cortisol, which destroys muscle mass. Stretching exercises, such as yoga and tai chi, can reduce levels of cortisol. Another personal trainer advocates the use of anabolic steroids for HIV-positive people. Injectable steroids used with exercise work best, but exercise alone can also be beneficial for fighting depression, AIDS-related wasting, and high blood pressure. An unpublished scientific study found a temporary drop in neutrophils and monocytes, two kinds of white blood cells, after aerobic exercise. These scientists still recommend moderate exercise done at an individual pace.