The effects of age and sex on mechanical ventilatory constraint and dyspnea during exercise in healthy humans

We examined the effects of age. sex, and their interaction on mechanical ventilatory constraint and dyspnea during exercise in 22 older (age = 68 +/- 1 yr; n = 12 women) and 22 younger (age = 25 +/- 1 y, n = 11 women) subjects. During submaximal exercise, older subjects had higher end-inspiratory (EILV) and end-expiratory (EELV) lung volumes than younger subjects (both P < 0.05). During maximal exercise, older subjects had similar EILV (P > 0.05) but higher EELV than younger subjects (P < 0.05). No sex differences in EILV or EELV were observed. We noted that women had a higher work of breathing (W-b) for a given minute ventilation ((V)over dot(E)) >= 65 1/min than men (P < 0.05) and older subjects had a higher W-b for a given (V)over dot(E) >= 60 1/min (P < 0.05). No sex or age differences in W-b were present at any submaximal relative (V)over dot(E). At absolute exercise intensities, older women experienced expiratory flow limitation (EFL) more frequently than older men (P < 0.05), and older subjects were more likely to experience EFL than younger subjects (P < 0.05). At relative exercise intensities, women and older individuals experienced EFL more frequently than men and younger individuals, respectively (both P < 0.05). There were significant effects of age. sex, and their interaction on dyspnea intensity during exercise at absolute, but not relative, intensities (all P < 0.05). Across subjects, dyspnea at 80 W was significantly correlated with indexes of mechanical ventilatory constraint (all P < 0.05). Collectively, our findings suggest age and sex have significant impacts on W-b, operating lung volumes, EFL, and dyspnea during exercise. Moreover, it appears that mechanical ventilatory constraint may partially explain sex differences in exertional dyspnea in older individuals. NEW & NOTEWORTHY We found that age and sex have a significant effect on mechanical ventilatory constraint and the perception of dyspnea during exercise. We also observed that the perception of exertional dyspnea is associated with indexes of mechanical ventilatory constraint. Collectively, our results suggest that the combined influences of age and biological sex on mechanical ventilatory constraint during exercise contributes, in part, to the increased perception of dyspnea during exercise in older women.