Is there a disassociation of maximal oxygen consumption and maximal cardiac output?

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Abstract
McCOLE, S. D., A. M. DAVIS, and P. T. FUEGER. Is there a disassociation of maximal oxygen consumption and maximal cardiac output? Med. Sci. Sports Exerc., Vol. 33, No. 8, 2001, pp. 1265–1269. Purpose The purpose of the present study was to determine whether maximal cardiac output (𝑄̇) is affected by the duration of the maximal exercise test. Methods Nine healthy men (N = 6) and women (N = 3) performed three separate maximal treadmill exercise tests, separated by at least 24 h, and underwent a body composition assessment by hydrostatic weighing, all within a 2-wk period. A baseline maximal exercise test was performed to establish V̇O2max. The second and third tests, assigned randomly, were designed to elicit the subjects’ predetermined V̇O2max in either 6 or 12 min. Heart rate (HR), blood pressure (BP), minutes of ventilation, and oxygen consumption (V̇O2) were measured during all tests. At the end of the 6- and 12-min tests, 𝑄̇ was measured using an acetylene rebreathing technique. Stroke volume (SV), mean arterial pressure (MAP), total peripheral resistance (TPR), and arteriovenous O2 difference were calculated using standard equations. Results Repeated-measures ANOVA indicated that there were no significant differences in HR and V̇O2max between the baseline, 6-min, and 12-min tests. Paired t-tests revealed significantly greater 𝑄̇ (25.1 ± 5.6 vs 23.7 ± 5.2 L·min−1) and SV (138.3 ± 31.5 vs 130.5 ± 31.2 mL) in the 6- versus 12-min tests, respectively. There were no significant differences in systolic BP, diastolic BP, MAP, TPR, or arteriovenous O2 difference. Conclusions Despite there being no difference in V̇O2max between the two tests, the 6-min maximal exercise test resulted in a significantly greater 𝑄̇ than the 12-min test, because of a significantly greater SV. Thus, there was a disassociation between V̇O2 and 𝑄̇ during maximal exercise.