Publikationsserver der RWTH Aachen University
Einfluss kurzzeitiger Immobilisation in 6 Kopftieflage auf die Kinetik des Muskelabbaus
Abstract
dc:descriptionThe aim of this study was to analyse, if there are any changes in muscle turnover after a short term bed rest in a -6° head down tilt position. Simultaneously with the measurements of the marker of muscle mass and breakdown such as kreatinine, 3 Methylhistidine, urea, serum protein and serum amino acid concentrations, we also determined a calf circumference and above all maximum voluntary plantar flexion force as a marker of muscle size and function. Eight healthy, male test subjects participated in this study which was performed in a randomized crossover design. Each of the two study phases consisted of 2 dietary adaptation days (ambulatory) and 11 days (24 h/day) in the metabolic ward [Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany]. The metabolic ward days were divided into a 4-day ambulatory period, a 6-day intervention period: either bed rest [-6° headdown tilt (HDT)] or non-bed rest, and 1 recovery day. The same sequence was repeated after a four day break. During both 11-day periods in the ward, constant room temperature (24°C) and relative humidity (50%) were ensured. Both study phases were identical with respect to environmental conditions, study protocol, and diet. During the bed rest phase, subjects were kept in bed for 24 h and were not allowed to elevate their heads > 30° from horizontal. Horizontal movement was allowed. All activities, including showering and weighing, were carried out either in horizontal or in the 6° HDT position. During the non-bed rest phase, the subjects were allowed to walk around in the ward. The volunteers received a diet according to dietary reference intake values of German association of nutrition. To avoid any impact of nutrients other than the controlled foods, the menu as well as the meal frequency and the dietary energy intake was identical during both phases. The data of our short-term bed rest study in a crossover design show that unloading of weightbearing muscles does not lead to increased excretion of markers of muscle mass, like creatinine, or of muscle breakdown, like urea and 3-Me-His excretion. Together with the unchanged excretion of these parameters, neither serum protein concentration nor serum amino acid concentration increased. The weight loss of all test persons was due to the fluid shift and changed fluid balance caused by increased urin excretion at the beginning of the immobilisation phase. There was a significant decrease of the 3,98% in the size of the calf muscles in the intervention group in comparisson with the non-bed rest group. The maximum voluntary calf muscle force velocity also showed a significant decrease by 6,2%. These results prove that after a short immobilisation in -6°HDT a significant decrease in the function of the calf muscles appear without a corresponding biochemical correlation.Therefore we conclude that- a short term immobilisation by means of a 6 day bed rest in a head down tilt position do not inevitably lead to a significant rise in muscle protein breakdown, - any change in muscle mass during bed rest is therefore most likely associated with a decrease in skeletal muscle protein synthesis rather than in protein breakdown, - the changes in serum amino acid concentration can not be varified without the measurement of the protein synthesis flows,- in future studies tracer dilution techniques and a longer term immobilisation phases should be included to analyse additional dynamic changes in protein metabolism.
Degree
thesis:*- Grantor dc:publisher
- Publikationsserver der RWTH Aachen University
- Year dc:date
- 2008
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Tomic, Aleksandra
- Contributors dc:contributor
-
- Gerzer, Rupert
Subjects
dc:subject × 15Rights
dc:rights- Statement dc:rights
-
- info:eu-repo/semantics/openAccess
- Language dc:language
- ger