Reliability and validity of measures of cardiac output during incremental to maximal aerobic exercise - Part II: Novel techniques and new advances

For exercise physiologists and sport cardiologists, one of the greatest cha llenges is to develop a valid, reliable, noninvasive and affordable measure of cardiac output ((Q) over dot). There are several techniques available t o measure Q during exercise conditions. These procedures generally provide accurate and reliable determinations of Q during submaximal exercise, but m ay be limited during maximal exercise conditions. The most commonly used no ninvasive measures are the acetylene (C2H2) and carbon dioxide (CO2) rebrea the methods as reviewed in part I of this article. Only the foreign gas reb reathe method, using C2H2, meets all of the criteria of being noninvasive, easy to use, reliable and valid for use during maximal exercise. New methodologies have recently been developed to measure (Q) over dot duri ng exercise conditions. Although not as popular as the C2H2 and CO2 rebreat he methods, these methods have increasingly gained favour in exercise physi ology and sport cardiology settings. The majority of these measures (if per formed meticulously), with the exception of impedance cardiography, provide reasonably accurate and reliable determinations of (Q) over dot. However, the cost of usage and technological limitations during maximal exercise hav e prevented these techniques from replacing the conventional measures of (Q ) over dot during exercise conditions. Doppler echocardiography and the mod ified C2H2 methods hold promise for the assessment of Q during maximal exer cise. With further advances in these technologies their use in exercise phy siology and sport cardiology settings may become more common.