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Eur J Appl Physiol. 2016 Mar;116(3):541-52. doi: 10.1007/s00421-015-3311-9. Epub 2015 Dec 24.

Fatigue sensation and gene expression in trained cyclists following a 40 km time trial in the heat.

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Department of Exercise and Sport Science, University of Utah, Salt Lake City, UT, USA.
Westmont College, 955 LaPaz Road, Santa Barbara, CA, 93108, USA.
Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA.
Department of Exercise and Sport Science, University of Utah, Salt Lake City, UT, USA.



We examined the effect of race-effort cycling exercise with and without heat stress on post-exercise perceptions of fatigue and pain, as well as mRNA expression in genes related to exercise responses.


Trained cyclists (n = 20) completed 40 km time trials during temperate (TC, 21 °C) and hot (HC, 35 °C) conditions. Blood lactates were measured 1 and 5 min post-exercise. Venous blood samples and ratings of fatigue and pain perceptions were obtained at baseline and at 0.5, 8, 24, and 48 h post-exercise. Leukocyte mRNA expression was performed for metabolite detecting, adrenergic, monoamine, and immune receptors using qPCR.


Significantly lower mean power (157 ± 32.3 vs 187 ± 40 W) and lactates (6.4 ± 1.7 vs 8.8 ± 3.2 and 4.2 ± 1.5 vs 6.6 ± 2.7 mmol L(-1) at 1- and 5-min post-exercise) were observed for HC versus TC, respectively (p < 0.05). Increases (p < 0.05) in physical fatigue and pain perception during TTs did not differ between TC and HC (p > 0.30). Both trials resulted in significant post-exercise decreases in metabolite detecting receptors ASIC3, P2X4, TRPV1, and TRPV4; increases in adrenergic receptors α2a, α2c, and β1; decreases in adrenergic β2, the immune receptor TLR4, and dopamine (DRD4); and increases in serotonin (HTR1D) and IL-10 (p < 0.05). Post-exercise IL-6 differed between TC and HC, with significantly greater increases observed following HC (p < 0.05).


Both TT performances appeared to be regulated around a specific sensory perception of fatigue and pain. Heat stress may have compensated for lower lactate during HC, thereby matching changes in metabolite detecting and other mRNAs across conditions.


ASIC; Heat stress; Metabolite; Muscle afferents; TRPV

[Indexed for MEDLINE]

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