title: Haemodynamic responses to physical activity and body posture during everyday life.
abstract: OBJECTIVE
  To determine the relationships between body posture and physical activity and systemic haemodynamics during everyday life.
  
  
  METHODS
  Continuous measurements were performed in 34 subjects (16 hypertensive, 12 male), aged 49 +/- 13 (mean +/- standard deviation) years. Blood pressure (BP) was measured in the brachial artery. Physical activity and posture were measured with four accelerometers. Beat-to-beat values of systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), stroke volume (SV), cardiac output (CO) and systemic vascular resistance (SVR) were computed from the pressure waveforms. Multiple correlation coefficients (R) between activity and haemodynamic variables were computed and responses to physical activity were estimated with random regression models.
  
  
  RESULTS
  The overall percentages of variance in SBP, DBP, HR, SV, CO and SVR explained by activity (R2) were 32, 28, 56, 44, 74, and 45%, respectively. The SBP and HR increased linearly with increasing levels of activity (19 mmHg and 30 beats/min when activity increased 90 percentiles). Other variables showed parabolic relationships. The initial decrease in SV and CO (14 ml and 0.5 l/min) and increase in DBP and SVR (9 mmHg and 2 mmHg min/l) with increasing levels of activity coincided with changes in posture (lying-sitting-standing). The subsequent SV and CO increase (23 ml and 3.7 l/min) and DBP and SVR decrease (8 mmHg and 8 mmHg min/l) coincided with changes in activity (standing-moving generally-walking).
  
  
  CONCLUSIONS
  Our findings show that normal daily posture and activity are only moderate determinants of BP, but main determinants of HR and CO variation.
authors.affiliation: Department of Internal Medicine, Erasmus MC, Rotterdam, The Netherlands. m.cavelaars@erasmusmc.nl
authors.forename: Marinel
authors.initials: M
authors.lastname: Cavelaars
authors.forename: Joke H M
authors.initials: JH
authors.lastname: Tulen
authors.forename: Jan H
authors.initials: JH
authors.lastname: van Bemmel
authors.forename: Paul G H
authors.initials: PG
authors.lastname: Mulder
authors.forename: Anton H
authors.initials: AH
authors.lastname: van den Meiracker
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology*; D003971:Diastole / Q000502:physiology; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D006973:Hypertension / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D013318:Stroke Volume / Q000502:physiology; D013599:Systole / Q000502:physiology; D014655:Vascular Resistance / Q000502:physiology