DIFFERENCES IN CARDIOVASCULAR ADAPTATIONS TO ENDURANCE EXERCISE TRAINING BETWEEN OLDER MEN AND WOMEN

Recent studies have shown that people in their seventh decade are able to adapt to exercise training with an increase in maximal O2 uptake (Vo2max) similar in relative magnitude to that observed in young people. The purpose of this study was to determine the relative contributions of increases in stroke volume and O2 extraction to the training-induced increase in Vo2max. in older men and women. Fifteen men [63 +/- 3 (SE) yr] and 16 women (64 +/- 3 yr), in good health, participated in 9-12 mo of endurance exercise training at 70 to 85% of maximal heart rate for 45 min/day, 4 days/wk. Vo2max increased 19% (2.35 +/- 0.1 to 2.8 +/- 0.1 l/min; P < 0.01) in the men and 22% (1.36 +/- 0.1 to 1.66 +/- 0.1 l/min; P < 0.01) in the women in response to training. In the men, stroke volume during maximal exercise was 15% higher after training, and this increase accounted for 66% of the increase in Vo2max. The remainder of the increase in Vo2max was accounted for by a 7% greater arteriovenous O2 content difference during maximal exercise. In contrast, training resulted in no change in stroke volume in women, in whom the entire increase in Vo2max was accounted for by a greater arteriovenous O2 content difference (12.2 +/- 0.4 before vs. 14.4 +/- 0.4 ml O2/100 ml blood after; P < 0.01) during maximal exercise. There were no changes in these variables in the control subjects. The mechanisms responsible for the training-induced increase in Vo2max in the older men were similar to those found in young people. However, the older women adapted to the exercise training with an increase in O2 extraction with no increase in cardiac output.