PULMONARY GAS-EXCHANGE AND VENTILATORY RESPONSES TO BRIEF INTENSE INTERMITTENT EXERCISE IN YOUNG TRAINED AND UNTRAINED ADULTS

To investigate pulmonary gas exchange and ventilatory responses to brief intense intermittent exercise and to study the effects of physical fitness on these responses, nine trained and nine untrained healthy male subjects aged 18-33 years performed the force-velocity (F-v) exercise test. This test consisted of 6-s sprints against increasing braking forces (F) separated by 5-min recovery periods. Oxygen uptake (VO2), carbon dioxide output (VCO2), and ventilation (V-E) magnitudes of their responses to the sprints were then calculated. For all subjects VO2 increased rapidly after beginning the sprints, and the peaks of the responses (F = 13.4; P < 0.001), end of recovery values (F = 6.5; P < 0.01), and VO2 magnitudes of response (F = 12.4; P < 0.001) rose significantly with the repetition of the sprints. The VO2 magnitudes of response correlated with the corresponding sprint power outputs (r = 0.55; P < 0.001) and with the sprint repetitions (r = 0.51, P < 0.001). The VCO2 (F = 7.1; P < 0.01) and V-E (F = 5.0; P < 0.01) peaks of response increased with the initial load incrementation, then stabilized when the subjects attained peak power output. End of recovery VCO2 (F = 18.0; P < 0.001) and V-E (F = 14.1; P < 0.001) values rose with increasing F. The F-v peak VO2, VCO2, V-E, tidal volume and respiratory frequency responses attained 53%, 40%, 44%, 66%, and 82% of the peak values measured at exhaustion of maximal graded exercise, respectively. Trained and untrained subjects had the same first sprint power output and braking force. Nevertheless, the trained subjects had higher VO2 peaks (F = 35.2; P < 0.001) and VO2 magnitudes of response (F = 30.0; P < 0.001) than the untrained subjects for all sprints. The higher peak VO2, values represented similar percentages of maximal oxygen uptake in the trained and untrained subjects. In summary, the present study showed that in brief intense intermittent exercise, i.e, the F-v test, the VO2, VCO2 and ventilatory responses in young subjects were submaximal with respect to the peak values attained at exhaustion of maximal graded exercise. The VO2 magnitude of response increase was related to the power output rise in the corresponding sprints and to the repetition of sprints. Moreover, the trained subjects presented higher VO2 peaks and magnitudes of response to the sprints than the untrained subjects.