Using the impedance cardiography method, heart rate (fc) matched changes on indexed stroke volume (SI) and cardiac output (CI) were compared in subjects engaged in different types of training. The subjects consisted of untrained controls (C), volleyball players (VB) who spent about half of their training time (360 min.week-1) doing anaerobic conditioning exercises and who had a maximal oxygen uptake (VO2max) 41% higher than the controls, and distance runners (D) who spent all their training time (366 min.week-1) doing aerobic conditioning exercises and who had a VO2max 26% higher than VB. The subjects performed progressive submaximal cycle ergometer exercise (10 W.min-1) up to fc of 150 beats.min-1. In group C, SI had increased significantly (P < 0.05) at fc of 90 beats.min-1 (+32%) and maintained this difference up to 110 beats.min-1, only to return to resting values on reaching 130 beats.min-1 with no further changes. In group VB, SI peaked (+54%) at fc of 110 beats.min-1, reaching a value significantly higher than that of group C, but decreased progressively to 22% of the resting value on reaching 150 beats.min-1. In group D, SI peaked at fc of 130 beats.min-1 (+54%), reaching a value significantly higher than that of group VB, and showed no significant reduction with respect to this peak value on reaching 150 beats.min-1. As a consequence, the mean CI increase per fc unit was progressively higher in VB than in C (+46%) and in D than in VB (+105%).(ABSTRACT TRUNCATED AT 250 WORDS)

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