Effects of aging and training status on ventilatory response during incremental cycling exercise

The aim of this study was to examine the effect of aging and training status on ventilatory response during incremental cycling exercise. Eight young (24 ± 5 yrs) and eight older (64 ± 3 yrs)competitive cyclists together with eight young (27 ± 4 yrs) and eight older (63 ± 2 yrs) untrained individuals underwent a continuous incremental cycling test to exhaustion to determine ventilatory threshold (VT), respiratory compensation point (RCP) and maximal oxygen uptake (VO2max). In addition, the isocapnic buffering (IB) phase was calculated together with the hypocapnic hyperventilation (HHV). VT occurred at similar relative exercise intensities in all groups, whereas RCP was recorded at higher intensities in young and older cyclists compared to the untrained subjects. The IB phase, reported as the difference between VT and RCP and expressed either in absolute [ml min-1 kg-1 VO2] or in relative terms, was greater (P< 0.01) in both young and older trained cyclists than in untrained subjects, who were also characterized by a lower exercise IB capacity. IB was particularly small in the older untrained volunteers. Although young untrained and older trained subjects had similar level of VO2max, older athletes exhibited a larger IB. In addition, a higher absolute but similar relative IB was observed in young vs older cyclists, despite a higher VO2max in the former. In conclusion, the present study shows that aging is associated with a reduction of the IB phase recorded during an incremental exercise test. Moreover, endurance training induces adaptations which result in an enlargement of the IB phase independent of age. This information 45 can be used for the characterization and monitoring of the physiological adaptations induced by endurance training.