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Test-retest errors and the apparent heterogeneity of training response
R J Shephard1, T Rankinen, C Bouchard
1Faculty of Physical Education and Health, University of Toronto, Toronto, Canada. royjshep@shaw.ca
European Journal of Applied Physiology
|October 18, 2003
Summary
Test-retest errors significantly inflate perceived differences in maximal oxygen intake (VO2max) gains from aerobic training. Accounting for measurement error reveals substantial, likely familial, individual variations in VO2max training response.
Area of Science:
- Exercise Physiology
- Human Performance
- Cardiorespiratory Fitness
Background:
- Published studies report wide inter-individual variability in maximal oxygen intake (VO2max) gains following aerobic conditioning programs.
- Observed VO2max gains exhibit a coefficient of variation (CV) of 8.4%, suggesting significant differences in training response.
Purpose of the Study:
- To evaluate the contribution of test-retest measurement errors to the apparent large inter-individual differences in VO2max training response.
- To re-evaluate the extent of true inter-individual differences in VO2max adaptation after accounting for measurement error.
Main Methods:
- Analysis of test-retest reliability of VO2max measurements in 742 healthy adults before and after a 20-week aerobic training program.
- Calculation of the effective coefficient of variation (CV) for VO2max data, considering single and paired observations.
- Estimation of the impact of measurement error on the standard deviation (SD) of training responses using two assumptions for 20-week test-retest error.
Main Results:
- The 2-day test-retest CV for VO2max was 5.0% before and 4.1% after training, with an effective weighted CV of 4.3% and 3.4%, respectively.
- Measurement error was estimated to contribute a CV of 5.5% to 6.1% (SD of 123-146 ml min(-1)) of apparent training responses.
- After accounting for measurement error, the SD for inter-individual differences in VO2max training response decreased from 202 ml min(-1) to 123-138 ml min(-1).
Conclusions:
- Test-retest measurement errors significantly inflate the perceived inter-individual differences in VO2max training response.
- While covariates like age and gender explain only 11% of the variance, measurement error plays a larger role than previously considered.
- Substantial inter-individual differences in VO2max training response persist even after accounting for measurement error, suggesting a strong genetic or familial component.