Mechanisms of exercise limitation in HIV+ individuals

Cardiopulmonary exercise testing (CPX) is an important diagnostic tool for both clinical and research purposes in HIV positive (HIV+) individuals. Important information can be obtained from the gas exchange responses that can elucidate heart, lung, peripheral vascular, pulmonary vascular, and muscle abnormalities in this population. A large percentage of these patients are deconditioned, respond well to exercise training, and have no intrinsic limitation to exercise. Results of a progressively increasing CPX can be used to: 1) design an exercise prescription for aerobic training in HIV+ individuals; 2) identify and refer patients with subtle abnormalities of gas exchange for further diagnostic studies to exclude early infectious complications: and 3) evaluate the improvements in maximal oxygen uptake, lactic acidosis threshold, and gas exchange kinetics as result from an aerobic exercise training program. Gas exchange kinetic analysis of constant work rate tests can provide similar information in a nonmaximal, reproducible, readily obtainable format. Both progressively increasing and constant work rate CPX tests provide important information on the changes in oxygen flow from the environment to the exercising muscle that occur with aerobic exercise training. Finally, a case study involving the exercise prescription for HIV+ individuals is reviewed as well as the risk of transmission of HIV during competitive sports competition events.