Received September 15, 2005
Revised October 5, 2005
Accepted after revision October 25, 2005
Human/environmental and exercise physiology
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EFFECTS OF ENHANCED HUMAN CHEMOSENSITIVITY ON VENTILATORY RESPONSES TO EXERCISE
Glen E. Foster 1,
Donald C. McKenzie 2,
Andrew William Sheel 1*
1 The University of British Columbia, School of Human Kinetics
2 The University of British Columbia, Faculty of Medicine
* To whom correspondence should be addressed. E-mail: bill.sheel{at}ubc.ca.
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Abstract |
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The purpose of this study was to determine whether short duration intermittent hypoxia, and the subsequent augmentation of the hypoxic ventilatory response (HVR), would lead to an increase in ventilatory responses during sea level exercise. It was hypothesized that subjects exposed to short-duration intermittent hypoxia would have a greater increase in the ventilatory response to exercise compared to those exposed to long duration intermittent hypoxia. Subjects (n=17, male) were randomly assigned to short duration intermittent hypoxia (SDIH: 12% O2 separated by 5 min of normoxia for one hour) or long duration intermittent hypoxia (LDIH: 30 min of 12% O2). Both groups had 10 exposures over a twelve day period. The HVR was measured on day 1 and 12. Maximal oxygen consumption (VO2MAX) was determined using a ramped cycle exercise test. Maximal exercise data was not different between SDIH or LDIH groups or following intermittent hypoxia. Minute ventilation, tidal volume, and respiratory frequency were compared at 20, 40, 60, 80, and 100% of VO2MAX. There was no difference in the ventilatory responses at any intensity of exercise following the intermittent hypoxia period. The HVR was significantly increased following the intermittent hypoxia intervention. The relationships between HVR and VO2MAX were non-significant on Day 1 (r=0.30) and Day 12 (r=0.47) (P>0.05). Our findings point to a lack of functional significance of increasing HVR via intermittent hypoxia on sea level exercise ventilatory responses.
Key Words:
Exercise, Hypoxia, VO2,max
