Published Online
on January 27, 2003

A more recent version of this article appeared on February 11, 2003

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Submitted on November 15, 2002
Revised on December 16, 2002
Accepted on December 17, 2002

Aging and the Exercise Pressor Reflex in Humans

Troy A. Markel BA, Joseph C. Daley III MD, Cynthia S. Hogeman BSN, RN, Michael D. Herr PhD, Mazhar H. Khan MD, Kristen S. Gray MS, Allen R. Kunselman MA, and Lawrence I. Sinoway MD^*

From the Cardiology Division (T.A.M., C.S.H., M.D.H., M.H.K., K.S.G., L.I.S.), the Pulmonary, Allergy and Critical Care Division (J.C.D.), and the Department of Health Evaluation Sciences, (A.R.K.), Penn State College of Medicine, Hershey, Pa; and VA Medical Center, Lebanon, Pa (L.I.S.).

^* To whom correspondence should be addressed. E-mail: lsinoway{at}psu.edu.

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).

Methods and 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 (%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.

Key words: aging • exercise • reflex • blood flow

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