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The relationship between exercise intensity and the sweat lactate excretion rate
Michael J Buono1, Nanette V L Lee, Paul W Miller
1Department of Biology, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-7251, USA. mbuono@mail.sdsu.edu
The Journal of Physiological Sciences : JPS
|December 17, 2009
Summary
Higher exercise intensity increases lactate excretion rate but decreases sweat lactate concentration due to sweat dilution. This finding is crucial for understanding exercise metabolism and sweat gland activity.
Area of Science:
- Exercise Physiology
- Biochemistry
- Environmental Medicine
Background:
- Lactate concentration in sweat is often used as an indicator of metabolic activity during exercise.
- Understanding how exercise intensity affects sweat composition is crucial for accurate physiological monitoring.
Purpose of the Study:
- To investigate the impact of increasing exercise intensity on sweat lactate concentration and lactate excretion rate.
- To determine if sweat lactate concentration accurately reflects metabolic activity at different exercise intensities.
Main Methods:
- Eight healthy males underwent a 90-minute treadmill walking protocol in a controlled environmental chamber (35°C, 40% RH).
- Exercise intensity was varied at 60%, 70%, and 80% of maximum heart rate (HRmax) in 30-minute bouts.
- Sweat rate was measured volumetrically, and sweat lactate concentration ([lactate](sweat)) was analyzed to calculate the lactate excretion rate (LER).
Main Results:
- Sweat lactate concentration significantly decreased at 70% and 80% HRmax compared to 60% HRmax.
- Lactate excretion rate significantly increased with higher exercise intensities (70% and 80% HRmax).
- A significant inverse relationship was observed between sweat rate and sweat lactate concentration.
Conclusions:
- Increased exercise intensity elevates lactate production, as indicated by the rising LER.
- The dilution effect from increased sweat production at higher intensities lowers sweat lactate concentration.
- Sweat lactate concentration alone may not be a reliable indicator of metabolic activity during intense exercise due to sweat dilution.
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