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.
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Official URL: http://www.springerlink.com/content/qwu5571272411vu4/
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.
|Title:||Energy metabolism in intensively exercising calf muscle under a simulated orthostasis|
|Journal or Publication Title:||Pflügers Archiv, European Journal of Physiology|
|In ISI Web of Science:||Yes|
|Page Range:||pp. 1153-1163|
|Keywords:||Muscle physiology, Energy metabolism, Magnetic resoance spectroscopy, Orthostasis, Lower body negative pressure,|
|HGF - Research field:||Aeronautics, Space and Transport|
|HGF - Program:||Space|
|HGF - Program Themes:||W FR - Forschung unter Weltraumbedingungen|
|DLR - Research area:||Space|
|DLR - Program:||W FR - Forschung unter Weltraumbedingungen|
|DLR - Research theme (Project):||W - Vorhaben Beschleunigungsinduzierte Effekte (old)|
|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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