MUSCLE STRENGTH, SYMPTOM INTENSITY, AND EXERCISE CAPACITY IN PATIENTSWITH CARDIORESPIRATORY DISORDERS

The contribution of muscle strength to symptom intensity and work capa city was examined in normal individuals and patients with cardiorespir atory disorders. Respiratory muscle strengths (maximal inspiratory and expiratory pressures) and peripheral muscle strengths (leg extension, leg flexion, seated bench press, and seated row) were measured in 4,6 17 subjects referred for clinical exercise testing. Subjects then rate d the intensity of leg effort, discomfort with breathing (dyspnea), an d chest pain (Borg scale) during an incremental exercise task (100 kpm /min each minute) to capacity on a cycle ergometer. Subjects were clas sified into groups on the basis of pulmonary function, drug therapy fo r cardiac disorders, and the presence of chest pain during exercise wi th electrocardiographic changes indicative of myocardial ischemia. Res piratory and peripheral muscle strengths, normalized for differences i n age, sex, and height, were significantly reduced in patients with ca rdiorespiratory disorders compared with normal individuals. Muscle str ength was a significant contributor to symptom intensity and work capa city in both health and disease; a two-fold increase in muscle strengt h was associated with a 25 to 30% decrease in the intensity of both le g effort and dyspnea and a 1.4- to 1.6-fold increase in work capacity. These results emphasize the need for an integrative approach in the a ssessment and therapeutic management of exercise intolerance, which co nsiders the contribution of muscle weakness to excessive symptoms and reduced work capacity, in addition to the contribution of ventilatory, gas exchange, and circulatory impairments.