Impact of aging on the work of breathing during exercise in healthy men

This study examined the impact of aging on the elastic and resistive components of the work of breathing (W-b) during locomotor exercise at a given 1) ventilatory rate, 2) metabolic rate, and 3) operating lung volume. Eight healthy younger (25 +/- 4 yr) and 8 older (72 +/- 6 yr) participants performed incremental bicycle exercise, from which retrospective analyses identified similar ventilatory rates (approximately 40, 70, and 100 L.min(-1)), similar metabolic rates ((V)over dotO(2): approximately 1.2, 1.6, and 1.9 L.min(-1)), and similar lung volumes [inspiratory and expiratory reserve volumes (IRV/ERV: approximately 25/34%, 16/33%, and 13-34% of vital capacity]. W-b at each level was quantified by integrating the averaged esophageal pressure-volume loop, which was then partitioned into elastic and resistive components of inspiratory and expiratory work using the modified Campbell diagram. IRV was smaller in the older participants during exercise at ventilations of 70 and 100 L.min(-1) and during exercise at the three metabolic rates (P < 0.05). Mainly because of a greater inspiratory elastic and resistive W-b in the older group (P < 0.05), total W-b was augmented by 40%-50% during exercise at matched ventilatory and matched metabolic rates. When examined during exercise evoking similar lung volumes, total W-b was not different between the groups (P = 0.86). Taken together, although aging exaggerates total W-b during locomotor exercise at a given ventilatory or a given metabolic rate, this difference is abolished during exercise at a given operating lung volume. These findings highlight the significance of operating lung volume in determining the age-related difference in W-b during locomotor exercise.