title: Difference in Physiological Components of VO2 Max During Incremental and Constant Exercise Protocols for the Cardiopulmonary Exercise Test.
abstract: [Purpose] VO2 is expressed as the product of cardiac output and O2 extraction by the Fick equation. During the incremental exercise test and constant high-intensity exercise test, VO2 results in the attainment of maximal O2 uptake at exhaustion. However, the differences in the physiological components, cardiac output and muscle O2 extraction, have not been fully elucidated. We tested the hypothesis that constant exercise would result in higher O2 extraction than incremental exercise at exhaustion. [Subjects] Twenty-five subjects performed incremental exercise and constant exercise at 80% of their peak work rate. [Methods] Ventilatory, cardiovascular, and muscle oxygenation responses were measured using a gas analyzer, Finapres, and near-infrared spectroscopy, respectively. [Results] VO2 was not significantly different between the incremental exercise and constant exercise. However, cardiac output and muscle O2 saturation were significantly lower for the constant exercise than the incremental exercise at the end of exercise. [Conclusion] These findings indicate that if both tests produce a similar VO2 value, the VO2 in incremental exercise would have a higher ratio of cardiac output than constant exercise, and VO2 in constant exercise would have a higher ratio of O2 extraction than incremental exercise at the end of exercise.
authors.affiliation: Division of Health Science, Graduate School of Health Science, Kio University, Japan.
authors.forename: Junshiro
authors.initials: J
authors.lastname: Yamamoto
authors.affiliation: Department of Physical Therapy, Faculty of Health Science, Kio University, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Harada
authors.affiliation: Department of Physical Therapy, Faculty of Health Science, Kio University, Japan.
authors.forename: Akinori
authors.initials: A
authors.lastname: Okada
authors.affiliation: Department of Physical Therapy, Faculty of Health Science, Kio University, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Maemura
authors.affiliation: Department of Physical Therapy, Faculty of Health Science, Kio University, Japan.
authors.forename: Misaki
authors.initials: M
authors.lastname: Yamamoto
authors.affiliation: Division of Health Science, Graduate School of Health Science, Kio University, Japan.
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Tabira
keywords: Cardiopulmonary exercise test; Fick equation; Near-infrared spectroscopy