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

Abstract

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 [Controls: 66 (1.1) years; n = 10]; (3) to compare the maximum oxygen consumption (˙VO_2max) 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 ˙VO_2max of the trained Cyclists [54 (1.6) ml · kg⁻¹ · min⁻¹] was significantly higher (P < 0.05) than that of the Runners [48 (3.9) ml · kg⁻¹ · min⁻¹], whereas both groups possessed a significantly higher ˙VO_2max 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 ˙VO_2max. 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 ˙VO_2max suggests that run training results in enhanced cardiovascular performance during cycle ergometry.