Prediction of stroke volume during upper and lower body exercise in men and women

In this study, regression equations were derived to predict cardiac stroke volume (SV, mL/beat), measured by carbon dioxide rebreathing, from oxygen pulse (O2 pulse, mL/beat) measurements in healthy men (n = 25) and women (n = 12) during upper and lower body exercise at the ventilatory threshold. The equations for upper body exercise were as follows: men, Y = 10.21X - 1.0, SE = 13.0; r = 0.85; women, Y = 12.70X - 4.8, SE = 15.4, r = 0.78. The equations for lower body exercise were as follows: men, Y = 5.22X + 53.0, SE = 17.9, r = 0.76; women, Y = 7.41X + 27.1, SE = 13.5, r = 0.78. No significant differences (p > .05) were observed between the exercise modes for the slopes and intercepts of the regression equations in both genders. The relationships between O2 pulse and SV were indirectly validated by using raw data from previous studies that had used the direct Fick method to determine cardiac output (Q) for each exercise mode and gender. Comparisons between the values of SV reported in several studies that used direct and indirect methods to determine Q and those predicted from the current equations indicated an error that was usually within 10% of the reported values. These observations suggest that the equations derived for predicting SV from O2 pulse measurements at the ventilatory threshold are quite accurate and can be generalized to a variety of techniques currently used to determine Q.