The variability in VO2 response to exercise among subjects is reported to be closely related to the level of fitness of the particular subject. Fitness for a particular sport may be dictated to a large extent by different exercise training strategies as well as subject's predominant fibre type. Therefore we were interested in demonstrating VO2 response profiles of endurance- and sprint-type athletes at the four particular exercise intensity domains. Following approval from the Institutional Ethics Committee, six endurance-type athletes (End-As: mean VO2peak 58.46 ml.kg.min-1) and six sprint-type athletes (Spr-As: mean VO2peak 50.32 ml.kg-1.min-1)performed a ramp-incremental test on a cycle ergometer, to determine VO2peak and to estimate lactate threshold (qL). Each subject, subsequently, completed four constant-load tests at different intensities: 10 min at 90%qL (moderate) or to a target of 15 min (or limit of tolerance, if less) at 40%[Delta] (heavy), 80%[Delta] (very heavy) and 110% VO2peak (severe) -[Delta]being the difference between qL and VO2peak. The "fundamental" kinetics of VO2 were faster in the End-As than the Spr-As, evidenced by the shorter time constant (&tau) values: 26±6 sec vs 38±14 sec at moderate, 25±6 vs and 33±16 sec at heavy, 26±10 sec vs 31±18 sec at very heavy, and 24±4 sec vs 32±14 at severe work rates. This suggests that fibre-type related differences might influence the "fundamental" pulmonary O2 kinetics more than exercise intensity.