Effect of ageing on the ventilatory response and lactate kinetics during incremental exercise in man

We investigated the effects of age on breathing pattern, mouth occlusion pr essure, the ratio of mouth occlusion pressure to mean inspiratory flow, and venous blood lactate kinetics during incremental exercise. Mouth occlusion pressure was used as an index of inspiratory neuromuscular activity, and i ts ratio to mean inspiratory flow was used as an index of the "effective im pedance" of the respiratory system. Nine elderly male subjects [mean (SD) a ge: 68.1 (4.8) years] and nine young male subjects [mean (SD) age: 23.4 (1. 3) years] performed an incremental exercise test on a bicycle ergometer. Af ter a warm-up at 30 W, the power was increased by 30 W every 1.5 min until exhaustion. Our results showed that at maximal exercise, power output, brea thing pattern, and respiratory exchange values, with the exception of tidal volume and the "effective impedance" of the respiratory system, were signi ficantly higher in the young subjects. The power output and oxygen consumpt ion values at the anaerobic threshold were also significantly higher in the young men. At the same power output, the elderly subjects showed significa ntly higher values for minute ventilation, respiratory equivalents for oxyg en uptake and carbon dioxide output ((V) over dot CO2), mean inspiratory Gl ow, occlusion pressure and lactate concentration than the young subjects. A t the same (V) over dot CO2 below the anaerobic threshold (0.5, 0.75, 1.00 and 1.251 . min(-1)), minute ventilation and lactate concentration were als o significantly higher in the elderly subjects. We observed a significantly higher minute ventilation at (V) over dot CO2 values of 0.5, 0.75, 1.00(P < 0.001) and 1.25 l . min(-1) (P < 0.05) in the elderly men, and a signific antly higher lactate concentration at (V) over dot CO2 values of 1.00 (P < 0.05) and 1.25 l . min(-1) (P < 0.01). In conclusion, the ventilatory respo nse in elderly subjects is elevated in comparison with that in young subjec ts, both below and above the anaerobic threshold. This study demonstrates f or the first time that this ventilatory increase, both below and above the threshold, is partly due to an increased lactate concentration.