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Effect of exercise-induced dehydration on lactate parameters during incremental exercise.
R Van Schuylenbergh1, B Vanden Eynde, P Hespel
1Exercise Physiology and Biomechanics Laboratory, Department of Kinesiology, Faculty of Physical Education and Physiotherapy, K. U. Leuven, Tervuursevest 101, 3001 Leuven, Belgium.
International Journal of Sports Medicine
|December 2, 2005
Summary
Dehydration significantly impacts cyclists' training intensity zones. Heart rate is a more reliable indicator than power output during exercise when dehydration is a risk, as adequate rehydration is crucial for maintaining performance.
Area of Science:
- Exercise Physiology
- Sports Science
- Environmental Physiology
Background:
- Cyclists commonly use heart rate and power output zones, derived from lactate parameters during incremental exercise testing, to guide training intensity.
- Factors like dehydration can alter the relationship between physiological markers (heart rate, power output) and blood lactate levels.
Purpose of the Study:
- To investigate the impact of exercise-induced dehydration on lactate parameters during graded cycling exercise.
- To determine if dehydration affects heart rate or power output thresholds and mechanical efficiency.
Main Methods:
- Nine triathletes underwent two graded cycling tests to exhaustion, separated by a 2-hour endurance bout.
- Two hydration conditions were tested: adequate fluid replacement (EH) and non-prevented dehydration (DH).
- Lactate parameters, including the 4-mmol lactate threshold (OBLA) and maximal lactate steady state (MLSS) threshold (TH-Dm), were analyzed.
Main Results:
- Significant weight loss (2.5 kg) occurred in the dehydration (DH) condition compared to adequate hydration (EH, 0.5 kg).
- Heart rate at TH-Dm remained stable, but heart rate at OBLA increased by ~10 bpm post-exercise in both conditions.
- Power output at TH-Dm decreased by ~12% in DH post-exercise, while gross mechanical efficiency declined significantly only in the DH condition.
Conclusions:
- Heart rate is a more reliable metric than power output for monitoring training load in cyclists susceptible to dehydration.
- Adequate rehydration is essential for cyclists to maintain optimal mechanical efficiency and performance during exercise in dehydrating conditions.