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. 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

Timothy A VanHaitsma  1   2 , Alan R Light  3 , Kathleen C Light  3 , Ronald W Hughen  3 , Sarah Yenchik  4 , Andrea T White  4   3
Affiliations

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

Timothy A VanHaitsma et al. Eur J Appl Physiol. 2016 Mar.

Abstract

Purpose: 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.

Methods: 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.

Results: 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).

Conclusions: 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.

Keywords: ASIC; Heat stress; Metabolite; Muscle afferents; TRPV.

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