Oxygen cost of ventilation during incremental exercise to VO2 max.
OBJECTIVE
Evidence of significant oxygen requirements for ventilation during exercise (exercise hyperpnoea) prompted the investigation into whether the oxygen cost of ventilation affects the presence of a whole-body VO(2) plateau at maximal exercise. The purposes of this study were to: (i) use isocapnic hyperpnoea trials to determine the oxygen cost of ventilation (VO(2VENT)) across a range of ventilation (V(E)); (ii) determine the mean VO(2VENT) at maximal exercise expressed as a percentage of whole-body VO(2) max; and (iii) determine if a plateau in VO(2) is more evident when the VO(2VENT) is subtracted from whole-body VO(2) at maximal exercise.


METHODS
A total of 21 subjects performed a VO(2) max test on the cycle ergometer to determine the range of V(E) for each subject. From the initial VO(2) max test, nine V(E) values across the range of V(E) were selected for each subject and the oxygen cost of each was measured.


RESULTS
The mean maximal VO(2VENT) equalled 8.8 +/- 3.3% of VO(2) max and ranged from 5.0% to 17.6%. VO(2VENT) increased exponentially with increasing V(E), but there was considerable subject variability in the oxygen cost per litre of V(E) as V(E) increased. Subtracting the VO(2VENT) from whole-body VO(2) at maximal exercise increased the detection of a plateau in VO(2) at VO(2) max.


CONCLUSIONS
The data of the present study indicate that the VO(2VENT) is a significant portion of VO(2) max and may be a limiting factor of maximal exercise performance in some subjects.
Exercise Physiology Laboratories, The University of Texas at El Paso, TX 79902, USA. cvella@utep.edu
Chantal A
CA
Vella
Derek
D
Marks
Robert A
RA
Robergs
D000328:Adult; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D012016:Reference Values; D012132:Respiratory Muscles / Q000502:physiology*; D012146:Rest / Q000502:physiology