Excess CO2 output independent of hyperventilation during constant-load exercise

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Abstract

Gas exchange kinetics during constant-load exercise were measured to investigate the possibility that excess C02 output during exercise might not be dependent on hyperventilation. Five healthy males performed twelve minutes of cycle exercise, including two minutes of 0 W pedaling, at 20, 40, 50, 60, 70, and 80% of their maximal work rate (WRmax) determined on the basis of preliminary ramp exercise of 30 W/min. Minute ventilation, O2 uptake, and C02 output were measured breath-by-breath. Excess C02 output and C02 stores were calculated, assuming that the respiratory quotient (RQ) in tissue is constant during constant-load exercise and that the respiratory exchange ratio at the mouth level is equal to the RQ during the steady-state phase. Excess C02 output was observed at levels of WR greater than 40% WRmax after initial C02 storage, where Vco2/VE decreased gradually as though in parallel with the kinetics of C02 storage. Vo2/VE, however, appeared to be constant after the initial peak. These data suggest that VE is closely correlated with Vo2 rather than Vco2 during constant-load exercise, indicating that excess C02 output to compensate lactate production is independent of hyperventilation.

Original languageEnglish
Pages (from-to)437-446
Number of pages10
JournalJapanese Journal of Physical Fitness and Sports Medicine
Volume40
Issue number5
DOIs
Publication statusPublished - 1991

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Keywords

  • excess C02
  • exercise
  • gas exchange kinetics
  • hyperventilation

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

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