Influence of age and gender on cardiac output VO2 relationships during submaximal cycle ergometry

It is presently unclear how gender, aging, and physical activity status interact to determine the magnitude of the rise in cardiac output ((Q) over dot c) during dynamic exercise. To clarify this issue, the present study examined the (Q)over dot c-O-2 uptake ((V) over dot 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) over dot c (acetylene rebreathing), stroke volume ((Q) over dot c/heart rate) and whole body (V) over dot O-2 were measured at rest and during submaximal exercise intensities (40, 70, and similar to 90% of peak (V) over dot O-2). Baseline resting levels of Qc were 0.6-1.2 1/min less in the older groups. However, the slopes of the (Q) over dot c-(V) over dot O-2 relationship across submaximal levels of cycling were similar among all four groups (5.4-5.9 l/l). The absolute (Q) overdot c associated with a given (V)over dot O-2 (1.0-2.0 1/min) was also similar among groups. Resting and exercise stroke volumes (m1/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 peak (V) over dot 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 the (Q) over dot c-(V) over dot o(2) relationships during submaximal cycle ergometry among chronically endurance-trained individuals.