Sympathetic modulation of blood flow and O2 uptake in rhythmically contracting human forearm muscles
| Autor: | David O. Warner, Michael J. Joyner, Mark A. Warner, L. A. Nauss |
|---|---|
| Rok vydání: | 1992 |
| Předmět: |
Adult
Male Periodicity medicine.medical_specialty Sympathetic Nervous System Adolescent Sympathetic modulation Physiology Hemodynamics Blood Pressure Physical exercise Oxygen Consumption Forearm Physiology (medical) Internal medicine Supine Position medicine Humans business.industry Muscles Nerve Block Blood flow body regions Autonomic nervous system medicine.anatomical_structure Endocrinology Blood pressure Regional Blood Flow Vasoconstriction Peripheral nervous system Cardiology and Cardiovascular Medicine business Muscle Contraction |
| Zdroj: | American Journal of Physiology-Heart and Circulatory Physiology. 263:H1078-H1083 |
| ISSN: | 1522-1539 0363-6135 |
| DOI: | 10.1152/ajpheart.1992.263.4.h1078 |
| Popis: | This study tested the effects of sympathetically mediated changes in blood flow to active muscles on muscle O2 uptake (VO2) in humans. Four minutes of graded (15-80% of maximum voluntary contraction, MVC) rhythmic handgrip exercise were performed. Forearm blood flow (FBF) (plethysmography) and deep vein O2 saturation were measured each minute. Forearm O2 uptake was calculated using the Fick principle. In protocol 1, exercise was performed while supine and again while upright to augment sympathetic outflow to the active muscles. Standing reduced FBF at rest from 3.6 to 2.2 ml.100 ml-1.min-1 (P < 0.05). During light exercise (15-40% MVC) FBF was unaffected by body position. Standing reduced FBF (P < 0.05) from 36.0 to 25.2 ml.100 ml-1.min-1 and forearm VO2 from 38.2 to 28.1 ml.kg-1.min-1 during the final work load. In protocol 2, exercise was performed while supine before and after local anesthetic block of the sympathetic nerves to the forearm. Sympathetic block increased FBF at rest from 3.1 to 8.9 ml.100 ml-1.min-1 (P < 0.05), and FBF was higher during all work loads At 70-80% of MVC sympathetic block increased FBF from 35.4 to 50.7 ml.100 ml-1.min-1 (P < 0.05), and forearm VO2 from 45.5 to 54.2 ml.kg-1.min-1 (P < 0.05). These results suggest that in humans sympathetic nerves modulate blood flow to active muscles during light and heavy rhythmic exercise and that this restraint of flow can limit O2 uptake in muscles performing heavy rhythmic exercise. |
| Databáze: | OpenAIRE |
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