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Physiological responses at five estimates of critical velocity
Anthony J Bull1, Terry J Housh, Glen O Johnson
1Department of Exercise Science and Athletic Training, Creighton University, 2500 California Plaza, KFC 225, Omaha, NE 68178, USA. abull@creighton.edu
European Journal of Applied Physiology
|December 20, 2007
Summary
Critical velocity (CV) estimates vary significantly between models, with nonlinear models yielding lower values. Most CV estimates do not represent a fatigueless exercise intensity, challenging their use in demarcating exercise domains.
Area of Science:
- Exercise Physiology
- Sports Science
- Biophysics
Background:
- Critical velocity (CV) is a physiological index used to predict endurance performance.
- Accurate estimation of CV is crucial for exercise prescription and understanding training domains.
- Various mathematical models exist for estimating CV, but their validity and comparability are not fully established.
Purpose of the Study:
- To compare critical velocity (CV) estimates derived from five distinct mathematical models.
- To analyze oxygen uptake (VO2) and heart rate (HR) responses during treadmill runs at these CV estimates.
- To evaluate the physiological implications of CV estimates in relation to exercise domains.
Main Methods:
- Ten subjects (6 males, 4 females) underwent an incremental test for VO2max determination.
- Subjects performed randomly ordered constant-velocity treadmill trials to estimate CV using two linear, two nonlinear, and one exponential model.
- Post-CV estimation, subjects completed runs to exhaustion at each estimated CV to monitor VO2 and HR.
Main Results:
- The 3-parameter nonlinear (Non-3) model yielded significantly lower CV estimates (P < 0.05) compared to other models.
- Most subjects could not complete 60 minutes of exercise at CV estimates from the Non-3 and Non-2 models.
- VO2 and HR responses indicated a VO2 slow component and significant increases in HR during runs at CV estimates from four models, suggesting these are not fatigueless intensities.
- Mean CV estimates varied by 18%, with four models falling within the heavy exercise domain.
Conclusions:
- Critical velocity (CV) estimates differ substantially across mathematical models, particularly nonlinear ones.
- Current CV estimation models may not accurately represent a fatigueless exercise intensity.
- CV may not serve as a precise demarcation point between heavy and severe exercise domains, necessitating further research into model selection and physiological validation.
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