Influence of age and gender on cardiac output-Vo2 relationships during submaximal cycle ergometry

Proctor, David N., Kenneth C. Beck, Peter H. Shen, Tamara J. Eickhoff, John R. Halliwill, and Michael J. Joyner. Influence of age and gender on cardiac output-V˙o 2 relationships during submaximal cycle ergometry. J. Appl. Physiol. 84(2): 599–605, 1998.—It is presently unclear how gender, aging, and physical activity status interact to determine the magnitude of the rise in cardiac output (Q˙c) during dynamic exercise. To clarify this issue, the present study examined theQ˙c-O2 uptake (V˙o 2) relationship during graded leg cycle ergometry in 30 chronically endurance-trained subjects from four groups ( n = 6–8/group): younger men (20–30 yr), older men (56–72 yr), younger women (24–31 yr), and older women (51–72 yr). Q˙c (acetylene rebreathing), stroke volume (Q˙c/heart rate), and whole bodyV˙o 2 were measured at rest and during submaximal exercise intensities (40, 70, and ∼90% of peakV˙o 2). Baseline resting levels of Q˙c were 0.6–1.2 l/min less in the older groups. However, the slopes of theQ˙c-V˙o 2relationship across submaximal levels of cycling were similar among all four groups (5.4–5.9 l/l). The absolute Q˙c associated with a given V˙o 2(1.0–2.0 l/min) was also similar among groups. Resting and exercise stroke volumes (ml/beat) were lower in women than in men but did not differ among age groups. However, older men and women showed a reduced ability, relative to their younger counterparts, to maintain stroke volume at exercise intensities above 70% of peakV˙o 2. This latter effect was most prominent in the oldest women. These findings suggest that neither age nor gender has a significant impact on theQ˙c-V˙o 2relationships during submaximal cycle ergometry among chronically endurance-trained individuals.