title: Baroreflex sensitivity during static exercise in individuals with Down Syndrome.
abstract: BACKGROUND
  Individuals with Down syndrome (DS) have altered heart rate (HR) and blood pressure (BP) responses to orthostatic challenges and isometric handgrip (IHG) exercise, suggesting possible alteration in baroreflex sensitivity.
  
  
  OBJECTIVE
  This study investigated baroreflex sensitivity (BRS) as a potential mechanism contributing to chronotropic incompetence during IHG in persons with DS.
  
  
  METHODS
  Heart rate and BP were continually recorded in 12 individuals with DS and 10 controls, at rest and during 2 min of IHG, at 30% of maximal voluntary contraction (MVC). Spontaneous BRS was derived via the sequence method.
  
  
  RESULTS
  No differences were seen in HR at rest between groups. Systolic BP (SBP) was significantly lower in the DS group at rest (106.1+/- 2.9 vs 116.5+/- 3.9 mm Hg, P < 0.05) and during IHG (123.9+/- 4.6 vs 150.1+/- 5.3 mm Hg, P<0.001). A significant group-by-task interaction was found for both change in HR and change in SBP with IHG, because of an attenuated HR and SBP response to IHG in participants with DS (P<0.05). When controlling for resting SBP, the DS group had a lower BRS at rest (16.0+/-1.7 vs 21.2+/-4.2 ms.mm Hg, P< 0.05) and during IHG (7.8 +/-1.0 vs 12.1+/- 2.6 ms.mm Hg, P< 0.05).
  
  
  CONCLUSIONS
  Individuals with DS have lower BRS at rest and during IHG than controls and this may be related to their attenuated HR response during perturbation.
authors.affiliation: Department of Kinesiology and Community Health University of Illinois at Urbana Champaign Champaign, IL 61820, USA.
authors.forename: Kevin S
authors.initials: KS
authors.lastname: Heffernan
authors.forename: Tracy
authors.initials: T
authors.lastname: Baynard
authors.forename: Styliani
authors.initials: S
authors.lastname: Goulopoulou
authors.forename: Ifigenia
authors.initials: I
authors.lastname: Giannopoulou
authors.forename: Scott R
authors.initials: SR
authors.lastname: Collier
authors.forename: Arturo
authors.initials: A
authors.lastname: Figueroa
authors.forename: Bo
authors.initials: B
authors.lastname: Fernhall
mesh_terms: D000328:Adult; D001145:Arrhythmias, Cardiac / Q000503:physiopathology*; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure; D016022:Case-Control Studies; D004314:Down Syndrome / Q000503:physiopathology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D011311:Pressoreceptors / Q000503:physiopathology*; D013599:Systole; D013997:Time Factors