Stroke volume response to cycle ergometry in trained and untrained older men

The aims of this study were threefold: (1) to investigate the stroke volume (SV) response of trained older male cyclists [Cyclists: 65 (2.1) years, n = 10] during incremental cycle ergometry (20 W.min-1); (2) to determine the SV dynamics and total peripheral resistance response of untrained, but healthy and active older male controls [ 66 (1.1) years; n = 10]; (3) to compare the maximum oxygen consumption (VO2max) and SV response of trained older male runners [Runners: 65 (3.4) years; n = 11] with that of age-matched Cyclists. Impedance cardiography was used to assess the response of cardiac output (CO), SV and total peripheral resistance to exercise involving cycle ergometry. The mean VO2max of the trained Cyclists [54 (1.6) ml.kg-1.min-1] was significantly higher (P < 0.05) than that of the Runner [48 (3.9) ml.kg-1.min-1], whereas both groups possessed a significantly higher VO2max than the CONTROLS [28 (1.3) ml.kg-1.min-1]. During exercise, at a heart rate of 90 beats.min-1, the SV of the Cyclists increased by 41%, that of the Runners increased by 47%, and that of the CONTROLS increased by 31%. However, the Cyclists' and Runners' SV response was significantly greater than that of the CONTROLS. The SV for cyclists and controls peaked at 30% of VO2max. This early increase in SV was a major factor underlying the increase in CO during exercise in both the trained and the untrained subjects. In addition, all three groups showed a significant decrease in total peripheral resistance throughout exercise. The finding that older male runners possessed a large exercise SV and high VO2max suggests that run training results in enhanced cardiovascular performance during cycle ergometry.