ABSTRACT
The upward drift of gas exchange variables during 70% maximal exercise and recovery half-times in aged and young subjects of equivalent age-predicted aerobic capacity was measured. In the aged subjects, upward drift of VE, VO2, and HR was reduced compared with the young group. The recovery of VE, VCO2, and VO2 was slowed in the aged. However, at 10 minutes post-exercise, VCO2, VO2, and HR had returned to similar relative values for both groups; in the young subjects VE remained elevated at the end of recovery. The reduced upward drift of gas exchange variables and HR during exercise in aged subjects is consistent with an attenuated response of glycogenolysis and lactate production to adrenergic stimulation and/or to selective loss of type II skeletal muscle fibers. The slowed recovery of VE, VCO2, and VO2 in elderly persons is consistent with age-related reduced CO2 chemosensitivity, delaying elimination of the exercise-induced CO2 load.
Subject(s)
Aging/physiology , Exercise/physiology , Heart Rate/physiology , Oxygen Consumption/physiology , Respiration/physiology , Adult , Aged , Carbon Dioxide/metabolism , Female , Humans , Male , Middle Aged , Pulmonary Gas Exchange/physiology , Time FactorsABSTRACT
Studies of the limited exercise capacity in patients with COPD have not assessed the recovery phase, although the phenomenon of increased oxygen uptake after exercise has been thoroughly investigated in normal subjects. Therefore, we compared the recovery of gas exchange variables and HR after maximal cycle ergometry in 16 patients with varying severities of airflow obstruction and ten aged control subjects. Aerobic capacity was reduced in the patients with COPD, and the rates of recovery of VE, VO2, VCO2, excess VCO2, and HR were all significantly slower in the patients with COPD than in the controls. When expressed as the half-time for recovery, patients with COPD had values which were approximately twice that of control subjects for gas exchange and HR. The extent of recovery was similar in patients and controls. We conclude that in patients with COPD, postexercise relative hyperpnea and hypermetabolism are significantly prolonged. In addition, impaired elimination of increased body stores of carbon dioxide may contribute to impaired adjustment to acid-base disorders in these patients.
