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Lactate threshold predicting time-trial performance: impact of heat and acclimation
Santiago Lorenzo1, Christopher T Minson, Tony G Babb
1Department of Human Physiology, University of Oregon, Eugene, OR 97403-1240, USA.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|April 30, 2011
Summary
Blood-based lactate threshold methods are more accurate for predicting cycling performance than ventilation-based methods, especially in hot conditions. Heat acclimation does not affect blood-based accuracy but worsens ventilation-based predictions.
Area of Science:
- Exercise Physiology
- Environmental Physiology
Background:
- Accurate assessment of exercise intensity is crucial for performance prediction in athletes.
- Lactate and ventilatory thresholds are commonly used to gauge exercise intensity.
- Environmental conditions, particularly heat, can influence physiological responses and threshold determination.
Purpose of the Study:
- To investigate the relationship between various lactate and ventilatory threshold methods and cycling performance.
- To compare the accuracy of these methods in cool versus hot environments.
- To examine the impact of heat acclimation on threshold determination and performance prediction.
Main Methods:
- Twelve cyclists underwent lactate threshold, maximal oxygen uptake, and 1-hour time trial tests in hot (38°C) and cool (13°C) conditions.
- Tests were performed before and after a heat acclimation period.
- Control subjects completed similar tests in a cool environment.
- Six blood- and ventilation-based lactate threshold methods were evaluated.
Main Results:
- Blood-based lactate threshold indexes showed higher correlations with time trial performance compared to ventilation-based indexes.
- Ventilation-based measures exhibited greater bias than blood-based measures, particularly in hot conditions.
- Heat acclimation exacerbated the overestimation bias of ventilation-based indexes but did not affect blood-based indexes.
- The inflection point (INFL) blood-based method was the most accurate predictor of time trial performance.
Conclusions:
- Blood-based lactate threshold determination methods are more reliable and less biased for predicting cycling performance than ventilation-based methods, especially in varying environmental conditions.
- Ventilation-based threshold predictions become less accurate in hot environments, particularly after heat acclimation.
- Blood-based methods, specifically the INFL method, maintain validity in predicting performance across both cool and hot conditions, even after heat acclimation.
