Cardiac output and oxygen uptake relationship during physical effort in men and women over 60 years old

This study investigated the relationship between oxygen uptake (VO(2)), cardiac output (Q), stroke volume (SV), and heart rate (HR) in 54 men and 77 women (age = 69 +/- 5 years) during incremental effort. Subjects performed a maximal cycle-ergometer test and VO(2) was directly measured. HR and SV were assessed by ECG and cardiograph impedance. Regression equations were calculated for Q-VO(2), HR-VO(2), and Q-HR relationships. The equations obtained for women were (a) Q (l min(-1)) = 2.61 + 4.67 VO(2) (l min(-1))(r(2) = 0.84); (b) HR (bpm) = 62.03 + 46.55 VO(2) (l min(-1)) (r (2) = 0.72); (c) SV (ml) 100:6[1 - e(-2.6 VO2 (1 min-1))] (r (2) = 0.41); (d) HR (bpm) = 41.48 + 9.24 Q (l min(-1)) (r (2) = 0.73). Equations for men were (a) Q (l min(-1)) = 2.52 + 5.70 VO(2) (l min(-1)) (r (2) = 0.89); (b) HR (bpm) = 66.31 + 32.35 VO(2) (l min(-1)) (r (2) = 0.72); (c) [1 - e(-1.7 VO2 (1 min-1))] (r (2) = 0.47); (d) HR (bpm) = 56.33 + 5.25 Q (l min(-1)) (r (2) = 0.69). The intercepts for Q-VO(2) and HR-VO(2) equations were similar for both genders, but the slopes were different (P < 0.05). The SV increased from baseline to 50-60% of VO(2) peak in both groups. No gender effect was found in SV increasing pattern, but the absolute values were in general higher for men (P > 0.05). A significant difference between men and women was observed for both slopes and intercepts in the Q-HR relationship (P < 0.05). In conclusion, (a) Q-VO(2) relation was linear during progressive effort; (b) regression intercepts were similar, but the slopes were higher for men compared to women; (c) SV-VO(2) relationship was nonlinear and maximum SV was reached at very submaximal workload; (d) older men exhibited higher Q upward potential as well higher SV but lower HR for a given submaximal workload than women of similar age.