STROKE VOLUME RESPONSE TO CYCLE ERGOMETRY IN TRAINED AND UNTRAINED OLDER MEN

The aims of this study were threefold: (1) to investigate the stroke v olume (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: 6 6(1.1) years; n = 10]1 (3) to compare the maximum oxygen consumption ( (V) over dot O-2max) and SV response of trained older male runners [Ru nners: 65 (3.4) years; n = II] with that of age-matched Cyclists. Impe dance cardiography was used to assess the response of cardiac output ( GO), SV and total peripheral resistance to exercise involving cycle er gometry. The mean (V) over dot O-2max of the trained Cyclists [54 (1.6 ) ml.kg(-1).min(-1)]was significantly higher (P < 0.05) than that of t he Runners [48 (3.9) ml.kg(-1).min(-1)], whereas both groups possessed a significantly higher (V) over dot O-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 in creased by 47%, and that of the Controls increased by 31%. However, th e Cyclists' and Runners' SV response was significantly greater than th at of the Controls. The SV for cyclists and controls peaked at 30% of (V) over dot O-2max. This early increase in SV was a major factor unde rlying 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 find ing that older male runners possessed a large exercise SV and high (V) over dot O-2max suggests that run training results in enhanced cardio vascular performance during cycle ergometry.