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

Abstract

This study investigated the relationship between oxygen uptake (VO₂), 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 VO₂ was directly measured. HR and SV were assessed by ECG and cardiograph impedance. Regression equations were calculated for Q–VO₂, HR–VO₂, and Q–HR relationships. The equations obtained for women were (a) Q (l min⁻¹) = 2.61 + 4.67 VO₂ (l min⁻¹)(r ² = 0.84); (b) HR (bpm) = 62.03 + 46.55 VO₂ (l min⁻¹) (r ² = 0.72); (c) ${\text{SV}\,{\text{(ml)}}}=100.6[1- {\text{e}}^{-2.6\; {\text{VO}_2}\;{(1\,{\text{min}}^{-1})}}]$ (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 VO₂ (l min⁻¹) (r ² = 0.89); (b) HR (bpm) = 66.31 + 32.35 VO₂ (l min⁻¹) (r ² = 0.72); (c) ${\text{SV}\,{\text{(ml)}}}=143.7[1- {\text{e}}^{-1.7\; {\text{VO}_2}\;{(1\,{\text{min}}^{-1})}}]$ (r ² = 0.47); (d) HR (bpm) = 56.33 + 5.25 Q (l min⁻¹) (r ² = 0.69). The intercepts for Q–VO₂ and HR–VO₂ equations were similar for both genders, but the slopes were different (P < 0.05). The SV increased from baseline to 50–60% of VO₂ 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–VO₂ relation was linear during progressive effort; (b) regression intercepts were similar, but the slopes were higher for men compared to women; (c) SV–VO₂ 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.