KINETICS OF EXCESS CARBON DIOXIDE OUTPUT DURING INTENSIVE EXERCISE AND RECOVERY

Abstract

1668 We investigated the kinetics of excess CO2 output during intensive exercise and recovery in male sprinters (SP: n=7) and long distance runners (LD: n=6). Each subject, after resting on a cycle ergometer for 5 min, performed an intensive exercise (356±45 watts, 90 rpm) until exhaustion. Gas exchange variables were obtained during the periods of rest, exercise and recovery (for 30 min). Blood lactate (La) was measured during the rest period, immediately after the end of exercise, and during recovery. End-tidal CO2 pressure (PETCO2) increased up to about 20 s after the end of exercise and then returned to its resting level at about 3 min of recovery. Thereafter, the PETCO2 level remained below the resting level. The difference between CO2 output and O2 uptake was defined as V̇CO2 excess. V̇CO2 excess was summed during the period until PETCO2 returned to the resting level. This was defined as the first phase of CO2 excess (F-CO2ex). The subsequent total V̇CO2 excess during the period until V̇CO2 excess returned to zero was defined as the second phase of CO2 excess (S-CO2ex). The ratio of F-CO2ex per body weight to the increase in La (the difference between La at peak and at rest) in LD was greater than that in SP. S-CO2ex per body weight in SP was greater than that in LD. The decrease in PETCO2 (the difference between PETCO2 at rest and at 10 min of recovery) was significantly higher in SP than in LD. S-CO2ex per body weight was significantly related to this decrease in PETCO2. Therefore, the difference between S-CO2ex per body weight in SP and LD was thought to depend on the difference in the amount of decrease in PETCO2.