Peripheral limiting factors during exercise in chronic lung diseases.
In normal subjects the sensation of general fatigue subjectively limits the physical performance, whereas in patients with reduced respiratory function the sensation of breathlessness is the common limiting symptom. Patients with chronic obstructive lung disease may adopt an intermittent exercise pattern (e.g. when climibing stairs), in which the work periods are brief in duration but relatively high in intensity. The immediate ventilatory demand can in that way be reduced. The local metabolism of the working muscles can meet the increased demand, which demonstrates that peripheral factors are unlikely to limit the physical performance in these patients. For evaluating the importance of peripheral factors limiting the exercise tolerance of daily activities, such as stair-climbing or walking uphill, such activities should specifically be studied considerating also the exercise pattern shown by the patient. Even in bronchitic patients with reduced arterial oxygen tension there are no evidence that the skeletal muscles are working under more anaerobic conditions than in normal persons at the same relative work load. The blood lactate as related to the heart rate usually lies within normal limits. In patients with respiratory failure, however, lack of energy supply from the energy rich compounds may develop. Thus, only in extreme situations can the exercise performance of the respiratory patients be expected to be specifically limited by peripheral factors. Physical inactivity leads to changes in the muscle metabolism as in normal persons with reduced aerobic capacity in the muscles. The specific effects of steroid treatment on the muscle function in patients with chronic obstructive disease have not been studied, but may be an important factor limiting muscular performance at certain types of exercises.
D006321:Heart / Q000503:physiopathology; D006801:Humans; D007773:Lactates / Q000097:blood; D008173:Lung Diseases, Obstructive / Q000503:physiopathology*; D009132:Muscles / Q000378:metabolism / Q000503:physiopathology; D010100:Oxygen / Q000097:blood; D005082:Physical Exertion; D012119:Respiration
D007773:Lactates; D010100:Oxygen