title: Physically active lifestyle enhances vagal-cardiac function but not central autonomic neural interaction in elderly humans.
abstract: The cause of the age-related impairment of arterial baroreflex function remains ill-defined; moreover, it is unknown whether this impairment results from aging per se or from an inactive lifestyle associated with aging. In this study, we sought to: 1) determine whether elderly individuals who maintained an active lifestyle had an enhanced carotid baroreflex function as compared with their sedentary counterparts; and 2) determine whether this difference was due in part to altered function of the arterial baroreceptor and/or altered central modulation. Eight healthy, sedentary (SED, 68+/-2 yr) and eight physically active (ACT, 68+/-1 yr) elderly men with peak O(2) consumption 25.5+/-1.2 vs 35.7+/-2.4 ml/min/kg (P<0.01), respectively, were assessed with carotid baroreceptor (CBR) function using 5s pulses of neck pressure or suction (ranging from +40 to -80 Torr) delivered to the carotid sinus region at rest and during lower body negative pressure (LBNP) of -15 and -40 Torr. Changes in heart rate (HR) and mean arterial pressure (MAP) were assessed for CBR-HR and CBR-MAP gains, respectively. Overall CBR-HR gains in a range of approximately 120 mmHg of carotid sinus pressure were greater (P<0.01) in ACT than SED at rest and during LBNP. The derived peak CBR-HR slopes between ACT and SED at rest were -0.32+/-0.07 vs -0.11+/-0.02 bpm/mmHg (P=0.007), respectively. However, there was no statistical difference (P=0.37) in CBR-MAP gains between the groups. Neither CBR-MAP (P=0.08) nor CBR-HR (P=0.41) gain was augmented by LBNP in the elderly.
  
  
  CONCLUSIONS
  Active lifestyle enhances the CBR-HR reflex sensitivity as a result of the improved vagal-cardiac function in elderly people. Aging is associated with an absence of central autonomic interaction in the control of blood pressure regardless of physical fitness.
authors.affiliation: Department of Integrative Physiology, University of North Texas Health Science Center at Fort Worth, Fort Worth, Texas 76107, USA. xshi@hsc.unt.edu
authors.forename: Xiangrong
authors.initials: X
authors.lastname: Shi
authors.forename: Frederick A
authors.initials: FA
authors.lastname: Schaller
authors.forename: Nancy
authors.initials: N
authors.lastname: Tierney
authors.forename: Patrick
authors.initials: P
authors.lastname: Chanthavong
authors.forename: Shande
authors.initials: S
authors.lastname: Chen
authors.forename: Peter B
authors.initials: PB
authors.lastname: Raven
authors.forename: Michael L
authors.initials: ML
authors.lastname: Smith
mesh_terms: D000368:Aged; D002320:Cardiovascular Physiological Phenomena; D002490:Central Nervous System / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D006321:Heart / Q000502:physiology; D006339:Heart Rate; D006801:Humans; D008019:Life Style; D008297:Male