title: Changes in heart rate and R-wave amplitude with posture.
abstract: BACKGROUND
  Effect of gravity on heart rate and blood pressure are well documented but the effect of posture on R-wave amplitude has not been studied.
  
  
  OBJECTIVE
  To investigate the effect of posture on the heart rate (HR) and R-wave amplitude (RWA).
  
  
  METHODS
  The electrocardiograph (ECG) was recorded in 20 young subjects on two occasions. A 5 minute recording of resting ECG was taken with the subject adopting the following postural cycle: lying, sitting, standing, sitting and lying positions.
  
  
  RESULTS
  The standing HR was significantly higher than that in sitting and lying positions, but the RWA was significantly lower in standing compared to the sitting and lying postures. The HR significantly increased at the initial phase of postural changes, irrespective of the position. For example, the HR increased from lying to sitting (66.6+/-2.3 to 85.0+/-10.9 beat x min(-1)) but also increased when changed from sitting to lying (70.6+/-10.6 to 85.2+/-8.7 beat x min(-1)).
  
  
  CONCLUSIONS
  Body posture has an effect on HR and RWA. The changes are probably related to orthostatic haemodynamic stress as well as changes in cardiac electrical axis. Whether the cause of the initial increase in the HR during postural change was attributed to skeletal muscle reflex or venous return requires further investigation.
authors.affiliation: Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Kowloon, Hong Kong.
authors.forename: A Y M
authors.initials: AY
authors.lastname: Jones
authors.forename: C
authors.initials: C
authors.lastname: Kam
authors.forename: K W
authors.initials: KW
authors.lastname: Lai
authors.forename: H Y
authors.initials: HY
authors.lastname: Lee
authors.forename: H T
authors.initials: HT
authors.lastname: Chow
authors.forename: S F
authors.initials: SF
authors.lastname: Lau
authors.forename: L M
authors.initials: LM
authors.lastname: Wong
authors.forename: J
authors.initials: J
authors.lastname: He
mesh_terms: D000328:Adult; D004562:Electrocardiography; D005260:Female; D006321:Heart / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D011187:Posture / Q000502:physiology*