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Type: Journal article
Title: Aging alters muscle reflex control of autonomic cardiovascular responses to rhythmic contractions in humans.
Author: Sidhu, S.
Weavil, J.
Venturelli, M.
Rossman, M.
Gmelch, B.
Bledsoe, A.
Richardson, R.
Amann, M.
Citation: American Journal of Physiology: Heart and Circulatory Physiology, 2015; 309(9):H1479-H1489
Publisher: American Physiology Society
Issue Date: 2015
ISSN: 0363-6135
Statement of
Simranjit K. Sidhu, Joshua C. Weavil, Massimo Venturelli, Matthew J. Rossman, Benjamin S. Gmelch, Amber D. Bledsoe, Russell S. Richardson and Markus Amann
Abstract: We investigated the influence of aging on the group III/IV muscle afferents in the exercise pressor reflex-mediated cardiovascular response to rhythmic exercise. Nine old (OLD; 68 ± 2 yr) and nine young (YNG; 24 ± 2 yr) males performed single-leg knee extensor exercise (15 W, 30 W, 80% max) under control conditions and with lumbar intrathecal fentanyl impairing feedback from group III/IV leg muscle afferents. Mean arterial pressure (MAP), cardiac output, leg blood flow (QL), systemic (SVC) and leg vascular conductance (LVC) were continuously determined. With no hemodynamic effect at rest, fentanyl blockade during exercise attenuated both cardiac output and QL ∼17% in YNG, while the decrease in cardiac output in OLD (∼5%) was significantly smaller with no impact on QL (P = 0.8). Therefore, in the face of similar significant ∼7% reduction in MAP during exercise with fentanyl blockade in both groups, LVC significantly increased ∼11% in OLD, but decreased ∼8% in YNG. The opposing direction of change was reflected in SVC with a significant ∼5% increase in OLD and a ∼12% decrease in YNG. Thus while cardiac output seems to account for the majority of group III/IV-mediated MAP responses in YNG, the impact of neural feedback on the heart may decrease with age and alterations in SVC become more prominent in mediating the similar exercise pressor reflex in OLD. Interestingly, in terms of peripheral hemodynamics, while group III/IV-mediated feedback plays a clear role in increasing LVC during exercise in the YNG, these afferents seem to actually reduce LVC in OLD. These peripheral findings may help explain the limited exercise-induced peripheral vasodilation often associated with aging. aging until the age of 80 years after which there is a more marked decline. Obesity and short stature are associated with reduced androgen status. Research into the age-related decline in androgen status should focus on the progressive accumulation of age-related comorbidities to better inform optimal clinical trial design.
Keywords: Leg
Muscle, Skeletal
Cardiovascular System
Femoral Artery
Autonomic Nervous System
Analgesics, Opioid
Cardiac Output
Regional Blood Flow
Muscle Contraction
Quadriceps Muscle
Cardiovascular Physiological Phenomena
Young Adult
Arterial Pressure
Rights: Copyright © 2015 the American Physiological Society
DOI: 10.1152/ajpheart.00433.2015
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