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Original articles  EXERCISE PHYSIOLOGY AND BIOMECHANICS 

The Journal of Sports Medicine and Physical Fitness 2002 June;42(2):152-7

Copyright © 2009 EDIZIONI MINERVA MEDICA

language: English

Kinetics of CO2 excessive expiration in constant-load exercise

Yano T., Horiuchi M., Yunoki T., Ogata H.

From the Laboratory of Exercise Physiology Graduate School of Education, Hokkaido University Sapporo, Japan


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Back­ground. The pur­pose of ­this ­study was to ­examine the ­kinetics of exces­sively ­expired CO2 (V.co2­excess) in ­response to an ­increase in ­blood lac­tate (La) ­during con­stant-­load exer­cise.
­Methods. O2 ­uptake (V.o2) and CO2 ­output (V.co2) ­were meas­ured at exer­cise inten­sities of 55% and 70% of indi­vidual ­peak ­values of V.o2 ­obtained in incre­mental exer­cise. V.co2 ­excess was ­obtained by mul­ti­plying the V.o2 ­obtained at 55% or 70% ­peakVoz by the dif­fer­ence ­between res­pir­a­tory gas ­exchange ­ratios (V.co2/V.o2) at 55% or 70% ­peak V.o2 and at 40% ­peakV.o2.
­Results. In ­both exer­cises of 55% and 70% ­peakV.o2, V.co2­excess ­remained con­stant for ­about the ­first ­minute, ­increased ­until ­about 2 min ­after the ­start of exer­cise, and ­then ­decreased. V.co2­excess ­showed pos­i­tive ­values ­even at 10 min ­after the ­start of exer­cise. The La ­level, on the ­other ­hand, ­increased ­during the ­first 5 min of exer­cise but did not ­show any sig­nif­i­cant ­change ­during the ­next 5 min. The ­values of V.co2­excess ­were inte­grated ­from the ­start to the end of 10 min of exer­cise (CO2­excess). CO2­excess was ­found to be sig­nif­i­cantly ­related to the dif­fer­ence ­between La at 10 min ­after the ­start of exer­cise and at ­rest (∆La). End ­tidal CO2 pres­sure (­Petco2) ­increased and ­then ­decreased in ­both exer­cises. The dif­fer­ence ­between ­Petco2 ­values at ­peak and at 10 min ­after the ­start of exer­cise (­∆Petco2) was sig­nif­i­cantly ­related to CO2­excess. ­∆Petco2 was ­also ­found to be sig­nif­i­cantly ­related to the ­increase in ∆La.
Con­clu­sions. The ­kinetics of esti­mated V.co2excess is ­affected ­first by the ­increase in La and ­later by the ­decrease in ­PETCO2 ­induced by the La ­increase.

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