Fig. 5.
The relationship between work of breathing and relative minute ventilation during incremental cycle exercise. Individual curves of the work of breathing vs. minute ventilation in older men and women (A) and younger men and women (B). Mean curves relating work of breathing to relative minute ventilation in all groups are shown in C. All mean curves are based on mean values of constants a and b from Eq. 1. Data for older men are displayed as thick gray lines, while data for older women are displayed as thick black lines. Data for younger men are displayed as thin gray lines, while data for older women are displayed as thin black lines. Wb, work of breathing; V̇e, minute ventilation. *P < 0.05, main effect of age, comparisons made between all older and all younger subjects, regardless of sex. †P < 0.05, comparisons made between all men and all women, regardless of age. No significant interaction effect was observed.