Relation between chest expansion, pulmonary function, and exercise tolerance in patients with ankylosing spondylitis

Thirty three patients with definite ankylosing spondylitis (AS) were examined to establish the relation between restriction of chest expansion, limitation of lung function, and working capacity or exercise tolerance. As in previous studies there was a significant association between chest expansion and lung vital capacity. There was also a significant association between vital capacity and exercise tolerance as measured by a subject's maximum oxygen capacity (VO2max). Both vital capacity and VO2max were expressed as a percentage of predicted normal values using patients' height before disease. In this study chest expansion did not have a significant effect on exercise tolerance. The results suggested that patients who took a modest amount of exercise regularly could maintain a satisfactory work capacity despite very restricted spinal and chest wall mobility. It is recommended that greater emphasis should be given to encouraging patients with AS to maintain cardiorespiratory fitness as well as spinal mobility.