Physical Training in Sedentary Middle-aged and Older Men III. Cardiac Output and Gas Exchange at Submaximal and Maximal Exercise

Abstract

Fifteen previously sedentary men (38–55 years old) participated in an endurance training program which consisted of running for 2–3 half-hours a week for 8–10 weeks. Maximal oxygen uptake increased in all subjects, mean increase from 2.68 to 3.06 l/min, i.e. 14 per cent. This increase was brought about by a 13 per cent increase in maximal cardiac output, from 18.7 to 21.1 l/min. Heart rate was 8–17 beats/min lower during submaximal exercise. The maximal heart rate decreased by 6 (from 182 to 176) beats/min. Thus stroke volume was increased 7–17 ml at submaximal and 17 ml (16 per cent) at maximal exercise. Heart volume determined from X-rays did not change. After the training, mean arterial blood pressure was on the average 5 mm Hg lower at a given submaximal oxygen uptake; no change was observed at maximal exercise.

Key Words:

• A-a oxygen gradient during exercise
• arterial blood pressure
• arterial P_CO2
• arterial pH
• arterial P_O2
• a-v oxygen difference
• heart rate
• maximal cardiac output
• stroke volume