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Maximal lactate steady state is altered in the heat
C L M de Barros1, T T Mendes, L Á C F Mortimer
1Federal University of Minas Gerais, School of Physical Education, Physiotherapy and Occupational Therapy, Belo Horizonte, Brazil. cristianolino@yahoo.com.br
International Journal of Sports Medicine
|May 19, 2011
Summary
Environmental heat significantly reduces maximal lactate steady state (MLSS) and ventilatory threshold (VT) workloads. Ventilatory threshold accurately estimates MLSS in hot conditions, despite lower absolute values.
Area of Science:
- Exercise Physiology
- Environmental Extremes
- Human Performance
Background:
- Maximal lactate steady state (MLSS) and ventilatory threshold (VT) are key indicators of endurance exercise capacity.
- Environmental factors, particularly heat, are known to impact physiological responses during exercise.
Purpose of the Study:
- To compare MLSS and VT in temperate (22°C) versus hot (40°C) environments.
- To assess the relationship between VT and MLSS workload under different thermal conditions.
Main Methods:
- Eight male subjects underwent cycle ergometer tests to determine peak workload (Wpeak), VT, and MLSS.
- Tests were conducted in both 22°C and 40°C (50% RH) conditions.
Main Results:
- Peak workload, MLSS workload, and VT workload were significantly lower in the hot environment compared to temperate conditions.
- Blood lactate concentration at MLSS was also reduced in the heat.
- Heart rate at VT was higher in the hot condition, while mean HR at MLSS was not significantly different.
Conclusions:
- Environmental heat significantly impairs exercise performance as indicated by reduced MLSS and VT workloads.
- VT can serve as a reliable indicator for estimating MLSS workload even in hot environments.
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