The aim of this study was to determine the effects of a prior run on the cardiorespiratory responses measured during a subsequent cycle segment. Twelve duathletes underwent three successive laboratory trials at an interval of one week: 1) an incremental cycle test, 2) 20 min of running followed by 20 min of cycling (RC), and 3) 20 min of control cycling (C) at the same intensity as the cycling segment of RC. Ventilatory data were collected every minute using a breath-by-breath automated system. Blood samples were collected to measure venous blood lactate concentration, [La], at rest, after the running and cycling segments of RC and after C. The results showed that the C segment of RC had significantly higher VE, VE/VO2, f and HR than C alone and significantly lower VT (p < 0.05) than C alone. Moreover, steady state during C of RC was reached at the 2nd min for VO2, VE, VCO2, VE/VO2, VE/VCO2, and VdT; at the 4th min for R and HR, and at the 5th min for f. The C of RC induced a significant increase in [La] in comparison with C alone. We concluded that the first minute of cycling after running during an RC trial induced specific metabolic and cardiorespiratory responses.