ORIGINAL ARTICLE Jacques Prioux á MicheÁ le Ramonatxo á Maurice Hayot Patrick Mucci á Christian Pre faut Effect of ageing on the ventilatory response and lactate kinetics during incremental exercise in man Received: 30 March 1999 / Accepted: 24 June 1999 Abstract We investigated the eects of age on breathing pattern, mouth occlusion pressure, the ratio of mouth occlusion pressure to mean inspiratory ¯ow, and venous blood lactate kinetics during incremental exercise. Mouth occlusion pressure was used as an index of in- spiratory neuromuscular activity, and its ratio to mean inspiratory ¯ow was used as an index of the ``eective impedance'' of the respiratory system. Nine elderly male subjects [mean (SD) age: 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 er- gometer. After a warm-up at 30 W, the power was in- creased by 30 W every 1.5 min until exhaustion. Our results showed that at maximal exercise, power output, breathing pattern, and respiratory exchange values, with the exception of tidal volume and the ``eective imped- ance'' of the respiratory system, were signi®cantly higher in the young subjects. The power output and oxygen consumption values at the anaerobic threshold were also signi®cantly higher in the young men. At the same power output, the elderly subjects showed signi®cantly higher values for minute ventilation, respiratory equivalents for oxygen uptake and carbon dioxide output ( _ V CO 2 ), mean inspiratory ¯ow, occlusion pressure and lactate concentration than the young subjects. At the same _ V CO 2 below the anaerobic threshold (0.5, 0.75, 1.00 and 1.25 l á min )1 ), minute ventilation and lactate concen- tration were also signi®cantly higher in the elderly sub- jects. We observed a signi®cantly higher minute venti- lation at _ V CO 2 values of 0.5, 0.75, 1.00 (P < 0.001) and 1.25 l á min )1 (P < 0.05) in the elderly men, and a sig- ni®cantly higher lactate concentration at _ V CO 2 values of 1.00 (P < 0.05) and 1.25 l á min )1 (P < 0.01). In con- clusion, the ventilatory response in elderly subjects is elevated in comparison with that in young subjects, both below and above the anaerobic threshold. This study demonstrates for the ®rst time that this ventilatory in- crease, both below and above the threshold, is partly due to an increased lactate concentration. Key words Ventilatory response á Exercise á Ageing á Lactate kinetics á Anaerobic threshold Introduction Many authors have studied the eects of age on the ventilatory response during exercise. Most have shown that the ventilatory response is higher in older subjects than in young subjects (DeVries and Adams 1972; Bri- schetto et al. 1984; McConnel and Davies 1992; Poulin et al. 1994). Brischetto et al. (1984) suggested that, during steady-state exercise below the anaerobic threshold (Th an ), the steeper slope of the minute venti- lation/carbon dioxide output ( _ V E = _ V CO 2 ) relationship in older subjects is a compensation for the higher dead- space ventilation. McConnel and Davies (1992), how- ever, postulated that this higher ventilatory response is entirely appropriate to metabolic demand. These authors did not think it likely that this increased ventilation is produced by increased lactic acidosis. Measurements of arterial blood gas tensions and pH were not performed in the preceding studies, however, even though at a given _ V CO 2 the values of this output for the elderly subjects corresponded to a higher per- centage of maximal aerobic power, and thus perhaps to a higher venous blood lactate concentration ([La]). Poulin et al. (1994) showed that other factors, such as an increase in central neurogenic drive or increases in exercise-related catecholamines and arterial potassium levels, may be related to the increased ventilatory re- sponse to exercise with ageing. This increase in central neurogenic drive may result from modi®cations in the mechanical characteristics of the respiratory system in the elderly. Indeed, Tolep and Kelsen (1991) and Enright et al. (1994) have shown that the maximal inspiratory Eur J Appl Physiol (2000) 81: 100±107 Ó Springer-Verlag 2000 J. Prioux (&) á M. Ramonatxo á M. Hayot á P. Mucci á C. PreÂfaut Laboratoire de Physiologie des Interactions, Service EFR, HoÃpital Arnaud de Villeneuve, F-34295, Montpellier Cedex 5, France e-mail: physio34@aol.com Tel.: +33-467-335908, Fax: +33-467-335923