title: Fatigue sensation and gene expression in trained cyclists following a 40 km time trial in the heat.
abstract: OBJECTIVE
  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.
authors.affiliation: Department of Exercise and Sport Science, University of Utah, Salt Lake City, UT, USA. tvanhaitsma@westmont.edu.|Westmont College, 955 LaPaz Road, Santa Barbara, CA, 93108, USA. tvanhaitsma@westmont.edu.
authors.forename: Timothy A
authors.identifier: http://orcid.org/0000-0002-0176-848X
authors.initials: TA
authors.lastname: VanHaitsma
authors.affiliation: Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA.
authors.forename: Alan R
authors.initials: AR
authors.lastname: Light
authors.affiliation: Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA.
authors.forename: Kathleen C
authors.initials: KC
authors.lastname: Light
authors.affiliation: Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA.
authors.forename: Ronald W
authors.initials: RW
authors.lastname: Hughen
authors.affiliation: Department of Exercise and Sport Science, University of Utah, Salt Lake City, UT, USA.
authors.forename: Sarah
authors.initials: S
authors.lastname: Yenchik
authors.affiliation: Department of Exercise and Sport Science, University of Utah, Salt Lake City, UT, USA.|Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA.
authors.forename: Andrea T
authors.initials: AT
authors.lastname: White
mesh_terms: D062565:Acid Sensing Ion Channels / Q000235:genetics / Q000378:metabolism; D000328:Adult; D001642:Bicycling / Q000502:physiology*; D005221:Fatigue; D005260:Female; D018869:Heat-Shock Response; D006358:Hot Temperature; D006801:Humans; D007378:Interleukins / Q000235:genetics / Q000378:metabolism; D019344:Lactic Acid / Q000097:blood; D008297:Male; D008875:Middle Aged; D017288:Pain Threshold; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D011941:Receptors, Adrenergic / Q000235:genetics / Q000378:metabolism; D050638:Receptors, Dopamine D4 / Q000235:genetics / Q000378:metabolism; D058848:Receptors, Purinergic P2X4 / Q000235:genetics / Q000378:metabolism; D050916:TRPV Cation Channels / Q000235:genetics / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism
chemical_list: C112231:ASIC3 protein, human; D062565:Acid Sensing Ion Channels; D007378:Interleukins; D012333:RNA, Messenger; D011941:Receptors, Adrenergic; D058848:Receptors, Purinergic P2X4; C495345:TLR4 protein, human; D050916:TRPV Cation Channels; C494482:TRPV1 protein, human; C416986:TRPV4 protein, human; D051197:Toll-Like Receptor 4; D050638:Receptors, Dopamine D4; D019344:Lactic Acid
keywords: ASIC; Heat stress; Metabolite; Muscle afferents; TRPV