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Circulating free-tryptophan to tyrosine as a marker of central fatigue during heat stress

From National Research Council Canada

DOIResolve DOI: https://doi.org/10.1249/01.MSS.0000401891.77191.43
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FormatText, Address
ConferenceAmerican College of Sports Medicine (ACSM) 58th Annual Meeting, May 31st-June 4th, 2011, Denver, CO
Abstract
One theory of central fatigue during exertional heat stress involves the influence on central nervous system activation of the changing ratio of serotonin and dopamine in key thermoregulatory centres in the brain. Circulating concentrations of the precursors, free-tryptophan (f-TRP) and tyrosine (TYR), respectively, compete for the same active carrier across the blood-brain-barrier. Thus, changes in the circulating ratio of f-TRP/TYR may be indicative of changing neurotransmitters in the brain and may help explain the different thermotolerance between endurance trained (TR) and untrained (UT). PURPOSE: The purpose was to examine the use of f-TRP/TYR as an indicator of impending fatigue in TR and UT males during acute uncompensable heat stress to exhaustion (EXH). METHODS: Twelve TR and eleven UT (Mean±SE: VO2peak= 70±2 and 50±1 mL·kgLBM⁻ ¹·min⁻ ¹, 11±1 and 16±1% fat, respectively) walked to EXH (Tre= 39.7 and 39.0°C, respectively) on a treadmill (4.5 km·h⁻ ¹, 2% grade) in 40°C and 30% R.H., wearing combat clothing and a protective hooded overgarment. Before and at a Tre of 38.0, 38.5, 39.0°C, and EXH, venous blood samples were obtained. Serum was analyzed for prolactin (PRL) using a chemiluminescent immunoassay, and plasma analyzed for f-TRP and TYR using gas chromatography/mass spectrometry.
Publication date
PublisherAmerican College of Sports Medicine / Wolters Kluwer
In
  • Medicine and Science in Sports and Exercise 43, no. 5: 682–682.
LanguageEnglish
Peer reviewedYes
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NPARC number23001378
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