Augmented sympathetic tone alters muscle metabolism with exercise: lack of evidence for functional sympatholysis
Deutscher übersetzter Titel: | Ein erhoehter sympathischer Tonus veraendert den Muskelstoffwechsel unter koerperlicher Belastung: das Fehlen eines Hinweises auf funktionelle Sympatholyse |
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Autor: | Shoemaker, J.K.; Pandey, P.; Herr, M.D.; Silber, D.H.; Yang, Q.X.; Smith, M.B.; Gray, K.; Sinoway, L.I. |
Erschienen in: | Journal of applied physiology |
Veröffentlicht: | 82 (1997), 6, S. 1932-1938, Lit. |
Format: | Literatur (SPOLIT) |
Publikationstyp: | Zeitschriftenartikel |
Medienart: | Gedruckte Ressource |
Sprache: | Englisch |
ISSN: | 8750-7587, 0021-8987, 0161-7567, 1522-1601 |
Schlagworte: | |
Online Zugang: | |
Erfassungsnummer: | PU199707205667 |
Quelle: | BISp |
Abstract des Autors
It is unclear whether sympathetic tone opposes dilator influences in exercising skeletal muscle. We examined high levels of sympathetic tone, evoked by lower body negative pressure (LBNP, -60 mmHg) on intramuscular pH and phosphocreatine (PCr) levels (31P-nuclear magnetic resonance spectroscopy) during graded rhythmic handgrip (30 contractions/min; ca. 17, 34, 52 and 69% maximal voluntary contraction). Exercise was performed with LBNP and without LBNP (Control). At the end of exercise, LBNP caused lower levels of muscle pH (6.59+/-0.09) compared with Control (6.78+/-0.05; P<0.05). PCr recovery, an index of mitochondrial respiration, was less during the recovery phase of the LBNP trial. Exercise mean arterial pressure was not altered by LBNP. The protocols were repeated with measurements of forearm blood flow velocity and deep venous samples (active forearm) of hemoglobin (Hb) saturation, pH, and lactate. With LBNP, mean blood velocity was reduced at rest, during exercise, and during recovery compared with Control (P<0.05). Also, venous Hb saturation and pH levels during exercise and recovery were lower with LBNP and lactate was higher compared with Control (P<0.05). We conclude that LBNP enhanced sympathetic tone and reduced oxygen transport. At high workloads, there was a greater reliance on nonoxidative metabolism. In other words, sympatholysis did not occur. Verf.-Referat