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Oxygen uptake to work rate relation throughout peak exercise in normal subjects: relevance for rate adaptive
T Lewalter1, H Rickli, D MacCarter
1Department of Medicine-Cardiology University of Bonn, Germany.
Pacing and Clinical Electrophysiology : PACE
|June 3, 1999
Summary
The relationship between oxygen uptake and work rate changes significantly at the anaerobic threshold during exercise. This finding is crucial for programming pacemakers, especially in women, to ensure optimal heart rate response during varying exercise intensities.
Area of Science:
- Exercise Physiology
- Cardiovascular Physiology
Background:
- The oxygen uptake to work rate (VO2/WR) relationship is utilized in rate-adaptive pacemaker programming.
- The specific VO2/WR curve characteristics relative to the anaerobic threshold (AT) remain underexplored.
Purpose of the Study:
- To investigate the VO2/WR slope below and above the AT in healthy individuals.
- To identify potential sex-based differences in the VO2/WR relationship at the AT.
Main Methods:
- Seventy-eight healthy subjects underwent symptom-limited ramping incremental treadmill exercise (RITE).
- Breath-by-breath gas exchange was monitored to determine VO2/WR slopes (rest-to-AT and AT-to-peak).
- Linear regression analysis was used to calculate slopes.
Main Results:
- A significant change in the VO2/WR slope was observed at the AT (31% decrease, P < 0.0001).
- Women exhibited a larger slope change at AT (43%) compared to men (22%, P < 0.01).
- The VO2/WR slope decreased at higher work intensities post-AT.
Conclusions:
- The AT represents a critical inflection point in the VO2/WR relationship during exercise.
- Pacemaker programming should account for the AT-related slope change for accurate rate response, particularly in women.
- Deviations in VO2/WR above AT may indicate overpacing.