title: Exercise tolerance and thermoregulatory responses during cycling in boys and men.
abstract: OBJECTIVE
  Physiological responses to exercise in the heat differ between prepubertal children and young adults. Whether these maturity-related variations imply lower exercise tolerance, inferior thermoregulation, and greater risk for heat injury in the child is uncertain. This study directly compared thermoregulatory and cardiovascular responses as well as endurance performance between prepubertal boys and adult males during steady-load cycling in moderately hot and cool ambient conditions with moderate humidity.
  
  
  METHODS
  Eight prepubertal boys (age 11.7 +/- 0.4 yr) and eight adult men (age 31.8 +/- 2.0 yr) performed steady-load cycling to exhaustion at an intensity equivalent to approximately 65% peak V O2 in both hot (approximately 31 degrees C) and cool (approximately 19 degrees C) environments, with fluid intake ad libitum.
  
  
  RESULTS
  Exercise duration in the heat was shorter for both groups (hot: men 30.46 +/- 8.84 min, boys 29.30 +/- 6.19 min; cold: men 42.88 +/- 11.79 min, boys 41.38 +/- 6.30 min), with no significant difference between men and boys (P > 0.05). Increases in rectal temperature, heart rate, and cardiac index were similar between groups and conditions. Stroke index, mean arterial pressure, and arterial venous oxygen difference were stable and similar in both conditions, without group differences. No significant dehydration was observed in men or boys.
  
  
  CONCLUSIONS
  This study failed to reveal differences in exercise tolerance, thermoregulatory adaptation, or cardiovascular response to exercise in the heat between euhydrated prepubertal boys and adult men.
authors.affiliation: Department of Pediatrics, Baystate Medical Center, Springfield, MA, USA. Thomas.rowland@bhs.org
authors.forename: Thomas
authors.initials: T
authors.lastname: Rowland
authors.forename: Sean
authors.initials: S
authors.lastname: Hagenbuch
authors.forename: David
authors.initials: D
authors.lastname: Pober
authors.forename: Anne
authors.initials: A
authors.lastname: Garrison
mesh_terms: D000328:Adult; D000367:Age Factors; D001642:Bicycling; D001833:Body Temperature Regulation / Q000502:physiology*; D002320:Cardiovascular Physiological Phenomena; D002648:Child; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D006358:Hot Temperature / Q000009:adverse effects; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D014481:United States