Effects of exercise training on α-adrenergic mediated pressor responses and baroreflex function in older subjects

R. J. Spina, R. E. Bourey, T. Ogawa, A. A. Ehsani

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10 Scopus citations

Abstract

Endurance exercise training increases maximal O2 uptake (V̇O2max) in older subjects, and training also improves cardiac function in older men. Although the effects of training on β-adrenergic responses have been investigated, little information is available regarding the effects of α- adrenergic responses and baroreflex function in older men and women. The purpose of the study was to determine whether endurance exercise training can affect α-adrenergic responses and baroreflex function in the elderly. We studied 13 men and women, 63 ± 4 yrs old (mean ± SE). V̇O2max was determined during treadmill exercise. Baroreflex function was determined from the change in heart rate (HR) relative to the change in systolic blood pressure (ΔHR/ΔSBP) during infusion of phenylephrine. V̇O2max was increased by 23% (1.9 ± 0.16 vs 2.34 ± 0.20 l/min; p < .01) in response to training. Maximal heart rate did not change, but HR during submaximal exercise at the same absolute exercise intensity was 17% lower after training. Resting heart rate was slower in the trained state. During α- adrenergic stimulation induced by graded doses of phenylephrine infusion, heart rate was lower after training because of training-induced bradycardia at rest. However, the elevation in systolic blood pressure (ΔSBP) and mean blood pressure (ΔMBP) from basal levels in response to a given dose of phenylephrine were significantly larger (ΔSBP: 18 ± 3 vs 26 ± 3 mmHg, p < .01; and ΔMBP 10 ± 2 vs 15 ± 3 mmHg, p < .01) after than before training. The doses of phenylephrine needed to raise systolic and diastolic blood pressure to comparable levels (SBP: 20 ± 3 and 21 ± 3 mmHg; DBP: 10 ± 2 and 11 ± 2 mmHg) were significantly smaller (p < .025 after training (SBP 0.64 ± 0.04 vs 0.44 ± 0.07 mg/min; DBP: 0.67 ± 0.04 vs 0.40 mg/min). The change in HR relative to the change in SBP (ΔHR/ΔSBP) was decreased from .67 ± .02 to .34 ± .06 in response to training (p < .05). The results suggest that endurance exercise training can enhance the α-adrenergic mediated vasopressor responses and reduce baroreflex function in older subjects. The increased pressor responses may protect against the possible adverse effects of reduced baroreflex function in the elderly.

Original languageEnglish
Pages (from-to)B277-B281
JournalJournals of Gerontology
Volume49
Issue number6
DOIs
StatePublished - 1994

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