title: Thermoregulation in boys and men exercising at the same heat production per unit body mass.
abstract: OBJECTIVE
  Child-adult thermoregulatory comparisons may be biased by differences in metabolic heat production ([Formula: see text]). We compared thermoregulatory responses of boys and men exercising at two intensities prescribed to elicit either a fixed [Formula: see text] per unit body mass (BM) or a fixed absolute [Formula: see text].
  
  
  METHODS
  Ten boys (10-12 years) and 10 men (19-25 years) performed 4 × 20-min cycling at a fixed [Formula: see text] per BM (W kg(-1)) at 35 °C and 35 % relative humidity (MENREL). Men also cycled (MENABS) at the same absolute [Formula: see text] (in W) as the boys.
  
  
  RESULTS
  [Formula: see text] was lower in boys compared with MENREL, but similar to MENABS (mean ± SD, 233.6 ± 38.4, 396.5 ± 72.3, 233.6 ± 34.1 W, respectively, P < 0.001). Conversely, [Formula: see text] per unit BM was similar between boys and MENREL, and lower in MENABS (5.7 ± 1.0, 5.6 ± 0.8 and 3.3 ± 0.3 W kg(-1), respectively; P < 0.001). The change in rectal temperature was similar between boys and MENREL (0.6 ± 0.2 vs. 0.7 ± 0.2 °C, P = 0.92) but was lower in MENABS (0.3 ± 0.2 °C, P = 0.004). Sweat volume was lower in boys compared to MENABS (500 ± 173 vs. 710 ± 150 mL; P = 0.041), despite the same evaporative heat balance requirement (E req) (199.1 ± 34.2 vs. 201.0 ± 32.7 W, P = 0.87).
  
  
  CONCLUSIONS
  Boys and men demonstrated similar thermoregulatory responses to 80 min of exercise in the heat performed at a fixed [Formula: see text] per unit BM. Sweat volume was lower in boys compared to men, despite similarities in absolute [Formula: see text] and E req.
authors.affiliation: Child Health & Exercise Medicine Program, Department of Pediatrics, McMaster University, 1280 Main Street West, HSC 3N27G, Hamilton, ON, L8S 4K1, Canada.
authors.forename: Gabriela T
authors.initials: GT
authors.lastname: Leites
authors.affiliation: Child Health & Exercise Medicine Program, Department of Pediatrics, McMaster University, 1280 Main Street West, HSC 3N27G, Hamilton, ON, L8S 4K1, Canada.|Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Giovani S
authors.initials: GS
authors.lastname: Cunha
authors.affiliation: Child Health & Exercise Medicine Program, Department of Pediatrics, McMaster University, 1280 Main Street West, HSC 3N27G, Hamilton, ON, L8S 4K1, Canada.
authors.forename: Joyce
authors.initials: J
authors.lastname: Obeid
authors.affiliation: Child Health & Exercise Medicine Program, Department of Pediatrics, McMaster University, 1280 Main Street West, HSC 3N27G, Hamilton, ON, L8S 4K1, Canada.
authors.forename: Boguslaw
authors.initials: B
authors.lastname: Wilk
authors.affiliation: Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Flavia
authors.initials: F
authors.lastname: Meyer
authors.affiliation: Child Health & Exercise Medicine Program, Department of Pediatrics, McMaster University, 1280 Main Street West, HSC 3N27G, Hamilton, ON, L8S 4K1, Canada. timmonbw@mcmaster.ca.
authors.forename: Brian W
authors.initials: BW
authors.lastname: Timmons
mesh_terms: D000293:Adolescent; D000328:Adult; D000375:Aging / Q000502:physiology*; D001833:Body Temperature Regulation / Q000502:physiology; D002648:Child; D003198:Computer Simulation; D004734:Energy Metabolism / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D018869:Heat-Shock Response / Q000502:physiology*; D006801:Humans; D008297:Male; D008954:Models, Biological; D005082:Physical Exertion / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013546:Sweating / Q000502:physiology*; D055815:Young Adult
keywords: Children; Dehydration; Exercise; Sweating; Temperature regulation