title: Chronotropic incompetence in persons with down syndrome.
abstract: OBJECTIVE
  To investigate the chronotropic response to exercise through peak heart rate and the Chronotropic Response Index (CRI) in participants with Down syndrome (DS) and in nondisabled control participants.
  
  
  METHODS
  Comparative study describing the acute exercise heart rate response.
  
  
  METHODS
  University sports medicine facility.
  
  
  METHODS
  Twenty participants with DS (mean age +/- standard deviation, 24.2+/-3.5y) and 20 control participants without disabilities (age, 21.2+/-2.8y).
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  Maximal treadmill exercise tests with metabolic and heart rate measurements. Maximal heart rate and the CRI were considered main outcomes.
  
  
  RESULTS
  The peak oxygen consumption (41.7 vs 31.8mL. kg(-1).min(-1)) and peak heart rate (165+/-14.7 vs 192+/-7.7 beats/min) were significantly lower in participants with DS than in controls (P<.05). The CRI was below normal (.84+/-.25) in participants with DS and was normal (.97+/-.07) in controls.
  
  
  CONCLUSIONS
  Both the CRI and the peak heart rates were indicative of chronotropic incompetence in participants with DS, but not in controls. The CRI of the participants with DS was similar to that reported for nondisabled populations who have a true chronotropic response to exercise. The CRI indicated that the low peak heart rate in our participants with DS was a true chronotropic response.
authors.affiliation: Physical Activity and Sports Sciences Department, Fundacío Blanquera, University Ramon Llull, Barcelona, Spain.
authors.forename: Myriam
authors.initials: M
authors.lastname: Guerra
authors.forename: Natalia
authors.initials: N
authors.lastname: Llorens
authors.forename: Bo
authors.initials: B
authors.lastname: Fernhall
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D004314:Down Syndrome / Q000378:metabolism / Q000534:rehabilitation*; D015444:Exercise; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D010101:Oxygen Consumption