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THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS
A Journal on Applied Physiology, Biomechanics, Preventive Medicine,
Sports Medicine and Traumatology, Sports Psychology
Indexed/Abstracted in: Chemical Abstracts, CINAHL, Current Contents/Clinical Medicine, EMBASE, PubMed/MEDLINE, Science Citation Index Expanded (SciSearch), Scopus
Impact Factor 1,111
Original articles EXERCISE PHYSIOLOGY AND BIOMECHANICS
The Journal of Sports Medicine and Physical Fitness 2002 June;42(2):152-7
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
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.