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Attenuated relationship between cardiac output and oxygen uptake during high-intensity exercise
J D Trinity1, J F Lee, M D Pahnke
1Human Performance Laboratory, Department of Kinesiology and Health Education, The University of Texas at Austin, USA. joel.trinity@utah.edu
Aim:
Recent findings have challenged the belief that the cardiac output (CO) and oxygen consumption (VO(2) ) relationship is linear from rest to maximal exercise. The purpose of this study was to determine the CO and stroke volume (SV) response to a range of exercise intensities, 40-100% of VO(2max), during cycling.
Methods:
Ten well-trained cyclists performed a series of discontinuous exercise bouts to determine the CO and SV vs. VO(2) responses.
Results:
The rate of increase in CO, relative to VO(2) , during exercise from 40 to 70% of VO(2max) was 4.4 ± 1.4 L L(-1). During exercise at 70-100% of VO(2max) , the rate of increase in CO was reduced to 2.1 ± 0.9 L L(-1) (P = 0.01). Stroke volume during exercise at 80-100% of VO(2max) was reduced by 7% when compared to exercise at 50-70% of VO(2max) (134 ± 5 vs. 143 ± 5 mL per beat, P = 0.02). Whole body arterial-venous O(2) difference increased significantly as intensity increased.
Conclusion:
The observation that the rate of increase in CO is reduced as exercise intensity increases suggests that cardiovascular performance displays signs of compromised function before maximal VO(2) is reached.
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