# Cardiac output

Cardiac output (Q) is the volume of blood your heart pumps per minute. It equals heart rate (HR, beats per minute) times stroke volume (SV, mL per beat). At rest, Q is 4 to 6 L/min. It rises to 20 to 25 L/min in healthy adults, and tops 40 L/min in elite endurance athletes. Oxygen delivery to your working muscles depends directly on Q. That makes Q the primary central limiter of VO2max. You can write it as VO2max = peak Q × peak arteriovenous oxygen difference (the a-vO2 diff). SV itself is shaped by ventricular preload, contractility, afterload, and the venous return from your skeletal-muscle pump. With healthy aging, both components decline. Maximal HR falls about 1 beat per minute per year. And SV drops, from poorer diastolic filling, a stiffer ventricle, and blunted beta-adrenergic response. Ogawa 1992 (Circulation, 148 men and women across four age decades) found that lower SV accounted for nearly 50% of the 25 to 32% age-related VO2max decline. Lower maximal HR and reduced peripheral oxygen extraction explained the rest. Pandey 2020 (JACC Heart Failure, 104 healthy volunteers) confirmed progressive age-related drops in peak cardiac index and peak SV during upright exercise, independent of body size. Endurance training raises peak Q, by expanding plasma volume and remodeling the ventricle. HERITAGE (Wilmore 2001, 631 sedentary adults aged 17 to 65) showed significant Q and SV gains at standardized submaximal workloads after 20 weeks, across sex, race, and age. But the training-induced SV gain is markedly weaker in older adults.

## Sources

- Ogawa T, Spina RJ, Martin WH 3rd, Kohrt WM, Schechtman KB, Holloszy JO, et al.. (1992). Effects of aging, sex, and physical training on cardiovascular responses to exercise.. Circulation. https://doi.org/10.1161/01.cir.86.2.494
- Wilmore JH, Stanforth PR, Gagnon J, Rice T, Mandel S, Leon AS, et al.. (2001). Cardiac output and stroke volume changes with endurance training: the HERITAGE Family Study.. Medicine & Science in Sports & Exercise. https://doi.org/10.1097/00005768-200101000-00016
- Pandey A, Kraus W, Brubaker P, Kitzman D. (2020). Healthy Aging and Cardiovascular Function: Invasive Hemodynamics During Rest and Exercise in 104 Healthy Volunteers.. JACC: Heart Failure. https://doi.org/10.1016/j.jchf.2019.08.020

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_Canonical: https://longevity-switzerland.com/en/glossary/cardiac-output · Part of Longevity Cities · Updated 2026-06-22_