title: The acute testosterone, growth hormone, cortisol and interleukin-6 response to 164-km road cycling in a hot environment.
abstract: This study investigated the acute endocrine responses to a 164-km road cycling event in a hot environment. Thirty-four male experienced cyclists (49.1 ± 8.3 years, 86.8 ± 12.5 kg, 178.1 ± 5.1 cm) participating in a 164-km road cycling event were recruited. Blood samples were collected within 0.3-2.0 h before the start (PRE: ~0500-0700 h) and immediately following the ride (POST). Samples were analysed for testosterone, growth hormone (GH), cortisol and interleukin-6 (IL-6). The temperature and humidity during the event were 35.3 ± 4.9°C and 47.2 ± 14.0%, respectively. Based on the finishing time, results for the fastest (FAST, 305 ± 10 min) and the slowest (SLOW, 467 ± 31 min) quartiles were compared. At POST, testosterone concentration was significantly (P < 0.05) lower (PRE, 20.8 ± 8.6; POST, 18.2 ± 6.7 nmol · L(-1)), while GH (PRE, 0.3 ± 0.1; POST, 2.3 ± 0.3 µg · L(-1)), cortisol (PRE, 661 ± 165; POST, 1073 ± 260 nmol · L(-1)) and IL-6 (PRE, 4.0 ± 3.4; POST, 22.4 ± 15.2 pg · mL(-1)) concentrations were significantly higher than those at PRE. At POST, GH and cortisol were significantly higher for the FAST group than for the SLOW group (GH, 3.6 ± 2.0 and 1.0 ± 0.8 µg · L(-1); cortisol, 1187 ± 209 and 867 ± 215 nmol · L(-1)). Participation in an ultra-endurance road cycling event in a hot environment induced significant acute changes in concentrations of circulating hormones, with a greater augmentation of GH and cortisol in those completing the ride fastest.
authors.affiliation: a Applied Physiology Laboratory, Department of Kinesiology, Health Promotion and Recreation , University of North Texas , Denton , TX 76203 , USA.|b Department of Biological Sciences , University of North Texas , Denton , TX 76203 , USA.
authors.forename: Jakob L
authors.initials: JL
authors.lastname: Vingren
authors.affiliation: a Applied Physiology Laboratory, Department of Kinesiology, Health Promotion and Recreation , University of North Texas , Denton , TX 76203 , USA.|b Department of Biological Sciences , University of North Texas , Denton , TX 76203 , USA.
authors.forename: Ronald G
authors.initials: RG
authors.lastname: Budnar
authors.affiliation: c Department of Kinesiology , University of Connecticut , Storrs , CT 06269 , USA.
authors.forename: Amy L
authors.initials: AL
authors.lastname: McKenzie
authors.affiliation: a Applied Physiology Laboratory, Department of Kinesiology, Health Promotion and Recreation , University of North Texas , Denton , TX 76203 , USA.|b Department of Biological Sciences , University of North Texas , Denton , TX 76203 , USA.
authors.forename: Anthony A
authors.initials: AA
authors.lastname: Duplanty
authors.affiliation: a Applied Physiology Laboratory, Department of Kinesiology, Health Promotion and Recreation , University of North Texas , Denton , TX 76203 , USA.|b Department of Biological Sciences , University of North Texas , Denton , TX 76203 , USA.
authors.forename: Hui-Ying
authors.initials: HY
authors.lastname: Luk
authors.affiliation: a Applied Physiology Laboratory, Department of Kinesiology, Health Promotion and Recreation , University of North Texas , Denton , TX 76203 , USA.|b Department of Biological Sciences , University of North Texas , Denton , TX 76203 , USA.
authors.forename: Danielle E
authors.initials: DE
authors.lastname: Levitt
authors.affiliation: c Department of Kinesiology , University of Connecticut , Storrs , CT 06269 , USA.
authors.forename: Lawrence E
authors.initials: LE
authors.lastname: Armstrong
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology*; D006358:Hot Temperature; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D006813:Humidity; D006854:Hydrocortisone / Q000097:blood*; D015850:Interleukin-6 / Q000097:blood*; D008297:Male; D008875:Middle Aged; D010807:Physical Endurance / Q000502:physiology; D013739:Testosterone / Q000097:blood*
chemical_list: C508600:IL6 protein, human; D015850:Interleukin-6; D019382:Human Growth Hormone; D013739:Testosterone; D006854:Hydrocortisone
keywords: Cycling; endocrine; endurance; exercise