title: Cardiovascular autonomic control during short-term thermoneutral and cool head-out immersion.
abstract: BACKGROUND
  Moderately cold head-out water immersion stimulates both baro- and cold-receptors, and triggers complex and contradictory effects on the cardiovascular system and its autonomic nervous control.
  
  
  OBJECTIVE
  To assess the effects of water immersion and cold on cardiovascular status and related autonomic nervous activity.
  
  
  METHODS
  Hemodynamic variables and indexes of autonomic nervous activity (analysis of heart rate and blood pressure variability) were evaluated in 12 healthy subjects during 3 exposures of 20 min each in the upright position, i.e., in air (AIR, 24-25 degrees C), and during head-out water immersion at 35-36 degrees C (WIn) and 26-27 degrees C (WIc).
  
  
  RESULTS
  Plasma noradrenaline, systolic and diastolic blood pressure, and total peripheral resistances were reduced during WIn compared to AIR (263.9 +/- 39.4 vs. 492.5 +/- 35.7 pg x ml(-1), 116.5 +/- 3.7 and 65.4 +/- 1.7 mmHg vs. 140.8 +/- 4.7 and 89.8 +/- 2.8 mmHg, 14.1 +/- 1.0 vs. 16.3 +/- 0.9 mmHg x L(-1) x min, respectively) while they were increased during WIc (530.8 +/- 84.7 pg ml(-1), 148.0 +/- 7.0 mmHg, 80.8 +/- 3.0 mmHg, and 25.8 +/- 1.9 mmHg x L(-1) x min, respectively). The blood pressure variability was reduced to the same extent during WIc and Win compared to AIR. Heart rate decreased during WIn (67.8 +/- 2.7 vs. 81.2 +/- 2.7 bpm during AIR), in parallel with an increased cardiac parasympathetic activity. This pattern was strengthened during WIc (55.3 +/- 2.2 bpm).
  
  
  CONCLUSIONS
  Thermoneutral WI lowered sympathetic activity and arterial tone, while moderate whole-body skin cooling triggered vascular sympathetic activation. Conversely, both WI and cold triggered cardiac parasympathetic activation, highlighting a complex autonomic control of the cardiovascular system.
authors.affiliation: Université de Franche Comté, Physiologie, Faculté de Médecine, Besançon, France. mourotlaurent@hotmail.com
authors.forename: Laurent
authors.initials: L
authors.lastname: Mourot
authors.forename: Malika
authors.initials: M
authors.lastname: Bouhaddi
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Gandelin
authors.forename: Sylvie
authors.initials: S
authors.lastname: Cappelle
authors.forename: Gilles
authors.initials: G
authors.lastname: Dumoulin
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Wolf
authors.forename: Jean Denis
authors.initials: JD
authors.lastname: Rouillon
authors.forename: Jacques
authors.initials: J
authors.lastname: Regnard
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001127:Arginine Vasopressin / Q000097:blood; D009320:Atrial Natriuretic Factor / Q000097:blood; D001341:Autonomic Nervous System / Q000378:metabolism / Q000502:physiology*; D001831:Body Temperature; D002307:Cardiography, Impedance; D002320:Cardiovascular Physiological Phenomena; D002319:Cardiovascular System / Q000294:innervation; D002395:Catecholamines / Q000097:blood; D003080:Cold Temperature; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D007101:Immersion; D008297:Male; D011187:Posture / Q000502:physiology; D013057:Spectrum Analysis; D014867:Water
chemical_list: D002395:Catecholamines; D014867:Water; D001127:Arginine Vasopressin; D009320:Atrial Natriuretic Factor