title: Aging and the exercise pressor reflex in humans.
abstract: BACKGROUND
  Blood flow limitation to exercising muscles engages the muscle reflex during exercise, evoking an increase in heart rate (HR), blood pressure (BP), and muscle sympathetic nerve activity (MSNA).
  
  
  RESULTS
  In the current study, we examined forearm flow and autonomic responses to ischemic handgrip in young and older subjects. We studied 6 younger subjects (mean age 23.5+/-2.2 years) and 7 older subjects (mean age 65.0+/-2.4 years). Subjects performed rhythmic handgrip (thirty 1-sec contractions/min) at 30% maximal voluntary contraction during six 1-minute stages: freely perfused exercise (E1) and exercise with forearm pressure of +10, +20, +30, +40, and +50 mm Hg (E2 through E6). We measured HR, BP, MSNA, forearm flow velocity, forearm venous oxygen saturation, H(+), and lactate. Compared with E1, ischemic exercise (E2 through E6) increased HR, BP, and MSNA, reduced forearm velocity, lowered venous oxygen saturation, and raised venous lactate and H(+). Compared with the younger subjects, the older subjects had attenuated BP at E6, attenuated MSNA indices (%(Delta)bursts, bursts/100 heart beats and signal averaged MSNA), attenuated H(+) at E6, a trend toward higher levels of oxygen saturation, and similar forearm velocity and HR responses.
  
  
  CONCLUSIONS
  Aging attenuates the muscle reflex.
authors.affiliation: Cardiology Division, Penn State College of Medicine, Hershey, PA, USA.
authors.forename: Troy A
authors.initials: TA
authors.lastname: Markel
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Daley
authors.forename: Cynthia S
authors.initials: CS
authors.lastname: Hogeman
authors.forename: Michael D
authors.initials: MD
authors.lastname: Herr
authors.forename: Mazhar H
authors.initials: MH
authors.lastname: Khan
authors.forename: Kristen S
authors.initials: KS
authors.lastname: Gray
authors.forename: Allen R
authors.initials: AR
authors.lastname: Kunselman
authors.forename: Lawrence I
authors.initials: LI
authors.lastname: Sinoway
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000502:physiology*; D001783:Blood Flow Velocity / Q000502:physiology; D001784:Blood Gas Analysis; D001794:Blood Pressure / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D005542:Forearm / Q000098:blood supply / Q000502:physiology; D018737:Hand Strength; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D005082:Physical Exertion / Q000502:physiology; D012016:Reference Values; D012018:Reflex / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology; D013564:Sympathetic Nervous System / Q000502:physiology
chemical_list: D019344:Lactic Acid