Wave Intensity Analysis: Sex-Specific Differences in Hemodynamic and Ventilatory Responses to Graded...

The differences in hemodynamic and ventilatory responses to graded exercise between men and women have not been well documented. Using wave intensity (WI) analysis, which is useful for analyzing ventriculo-arterial interaction, we aimed to elucidate the sex-specific differences.

We enrolled 48 healthy subjects (24 men and 24 women, age 21.3 ± 1.6 and 20.5 ± 0.9 years, n.s. [not significant]). Using ultrasonic diagnostic equipment, we measured WI, arterial stiffness parameter (β), force-frequency relation (FFR) and other hemodynamic parameters in the carotid artery before and during graded bicycle exercise. We also analyzed expired gas volume (VE) during the exercise. The workload was increased stepwise by 20 W at 1-min intervals up to respiratory compensation (RC) point through the anaerobic threshold (AT). WI is defined as WI = (dP/dt) (dU/dt), where P is blood pressure, U is velocity, and t is time. The peak value of WI (W₁) increases with left ventricular (LV) peak dP/dt, in other words, an index of cardiac contractility. The FFR was obtained as the linear regression line of W₁ on heart rate. β is defined as β = ln (Ps/Pd)/[(Ds - Dd)/Dd], where D is the arterial diameter, and suffixes s and d indicate systolic and diastolic, respectively.

There was no difference in the body mass index between men and women. Carbon dioxide outputs (VCO₂) did not differ at rest, but those at AT and RC were greater in men. Oxygen consumptions (VO₂) in men and women at rest did not differ, but those in men at AT and RC were greater. Workloads per body weight in men and women did not differ at AT, but they were greater in men at RC. Systolic pressures at rest, AT and RC were greater in men than women. Heart rates in men and women did not differ at any stage of the graded exercise. W₁ did not differ at rest and AT, but it was greater in men than women at RC. The slope of the FFR during the period from rest to AT did not differ between men and women. However, the slope of the FFR during the period from AT to RC was greater in men.

The reached values of workload/weight at RC, VCO₂ at AT and RC, VO₂ at AT and RC, W₁ at RC, and the slope of the FFR during the period from AT to RC were greater in men than women.