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Energy metabolism in intensively exercising calf muscle under a simulated orthostasis

Zange, Jochen and Beisteiner, Mareike and Müller, Klaus and Shushakov, Vladimir and Maassen, Norbert (2008) Energy metabolism in intensively exercising calf muscle under a simulated orthostasis. Pflügers Archiv, European Journal of Physiology, 455 (6), pp. 1153-1163. Springer Verlag.

Full text not available from this repository.

Official URL: http://www.springerlink.com/content/qwu5571272411vu4/

Abstract

We conducted non-invasive methods to investigate the mechanisms how an orthostasis improves fatigue resistance in human calf muscle during intense exercise. Eleven healthy volunteers performed two series of ten intervals of maximum dynamic exercise (15 s) and recovery (45 s) at almost horizontal body position under both, control conditions (CON) and lower body negative pressure (LBNP, -40 mbar). As from the second work interval, LBNP significantly improved fatigue resistance shown as a lower reduction in work and in contraction velocity (P < 0.01). During each work interval, EMG showed a small increase in amplitude (P < 0.01) and a steep drop by 20% in median frequency (P < 0.01). Under LBNP, both EMG parameters completely recovered during subsequent rest, whereas under CON recovery was incomplete (P < 0.01). During the first work interval, consumption of phosphocreatine (PCr) was almost the same for both conditions. In periods of recovery under LBNP, resynthesis of PCr and inorganic phosphate were significantly faster. PCr reached 10 to 20% higher levels (P < 0.01). LBNP caused an initial increase in intracellular pH (0.08 U (P < 0.01)). The subsequent time courses of pH were similar for CON and LBNP. During work, pH steeply increased by about 0.3 U. During subsequent recovery, pH dropped to values between 6.3 and 6.5. LBNP caused significantly higher levels of total haemoglobin and oxy-haemoglobin (P < 0.05). A simulated orthostasis increased fatigue resistance during high intense interval exercise because of a faster PCr resynthesis and may be because of improvements in the maintenance of motoneuronal activity.

Document Type:Article
Title:Energy metabolism in intensively exercising calf muscle under a simulated orthostasis
Authors:
AuthorsInstitution or Email of Authors
Zange, JochenUNSPECIFIED
Beisteiner, MareikeUNSPECIFIED
Müller, KlausUNSPECIFIED
Shushakov, VladimirMedizinische Hochschule Hannover
Maassen, NorbertMedizinische Hochschule Hannover
Date:March 2008
Journal or Publication Title:Pflügers Archiv, European Journal of Physiology
Refereed publication:Yes
In ISI Web of Science:Yes
Volume:455
Page Range:pp. 1153-1163
Publisher:Springer Verlag
Status:Published
Keywords:Muscle physiology, Energy metabolism, Magnetic resoance spectroscopy, Orthostasis, Lower body negative pressure,
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W FR - Forschung unter Weltraumbedingungen (old)
DLR - Research area:Space
DLR - Program:W FR - Forschung unter Weltraumbedingungen
DLR - Research theme (Project):W - Vorhaben Beschleunigungsinduzierte Effekte (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Aerospace Medicine > Space Physiology
Deposited By: Dr.rer.nat. Jochen Zange
Deposited On:18 Feb 2008
Last Modified:27 Apr 2009 14:27

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