A2 Refereed review article in a scientific journal
Cardiac output limits maximal oxygen consumption, but what limits maximal cardiac output?
Authors: Heinonen, Ilkka
Publisher: WILEY
Publishing place: HOBOKEN
Publication year: 2025
Journal: Experimental Physiology
Journal name in source: EXPERIMENTAL PHYSIOLOGY
Journal acronym: EXP PHYSIOL
Volume: 110
Issue: 5
First page : 666
Last page: 674
Number of pages: 9
ISSN: 0958-0670
eISSN: 1469-445X
DOI: https://doi.org/10.1113/EP091594
Web address : https://doi.org/10.1113/EP091594
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/492242328
Maximal oxygen uptake/consumption is an important variable determining exercise performance. It is generally considered to be limited largely, but not exclusively, by maximal cardiac output (CO), which limits the ability of heart to pump oxygen-rich arterial blood to working muscles. Cardiac output is a product of heart rate and stroke volume, which is the amount of blood ejected from the heart by one heart beat. Exercise training, especially of the endurance type, can increase maximal CO substantially. A straightforward way for the heart to increase maximal CO would be to increase maximal heart rate, but this does not happen; instead, maximal heart rate tends to be reduced after training. This is because heart rate is the most important determinant of myocardial oxygen consumption, and ventricular filling and myocardial blood flow (MBF) would be compromised by further increases in heart rate, given that MBF is blunted by contractions and occurs principally during diastole. Myocardial oxygen extraction is already high at rest and is increased further in endurance-trained athletes, making their hearts even more dependent on increases in MBF. The trained heart therefore also shows reduced MBF, enhanced blood mean transit time and higher myocardial vascular resistance at rest and during submaximal exercise, although MBF reserve is not improved. It follows logically that MBF is an important determinant of myocardial performance, and it is proposed in this review that cardiac afferent sensory nerves might contribute to controlling and limiting heart rate, hence maximal CO, in order to protect the heart from ischaemia.
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Funding information in the publication:
This review was written during my Academy Research Fellowship, funded by the Research Council of Finland (324243).
