Mechanical ventilatory constraints in aging, lung disease, and obesity; perspectives and brief review. Med. Sci. Sports Exerc., Vol. 31, No. 1 (Suppl.), pp. S12-S22, 1999. One of the most difficult tasks of cardiopulmonary exercise testing is to determine the influence of ventilatory limitations on the ventilatory response to exercise. Currently there is no generally accepted method in which to quantify the magnitude of mechanical ventilatory constraints during exercise. Nor is there agreement on how to quantify maximal ventilatory capacity. To address these issues, this article focuses on the evaluation of mechanical ventilatory constraints during exercise and provides an overview of the mechanical ventilatory constraints that are encountered with aging, lung disease, and obesity.