Assessment of relaxed and isometrically contracted skeletal muscle visco-elasticity in water immersion ergo-tub
- Paper number
IAC-08.A1.2.14
- Author
Dr. Ragnar Viir, University of Tartu, Estonia
- Coauthor
Dr. Alar Veraksitš, University of Tartu, Estonia
- Coauthor
Ms. Kristiina Rajaleid, Stockholm University, Sweden
- Coauthor
Prof. Mati Pääsuke, University of Tartu, Estonia
- Coauthor
Dr. Ahti Virkus, Mediverkko OY, Finland
- Year
2008
- Abstract
Purpose: On the land, the performance can be improved by training via neural and muscular adaptation - the first weeks of training mainly result in neural adaptations, while muscular adaptation requires more time. During spaceflight, the function of the musculoskeletal system, as well as other organ-systems, needs to be preserved against the subversive effect of zero-G. Regular exercise is required, but artificial gravity is proper countermeasure to resist changes in space. Weightlessness has been found to work also as a model for aging (1). Bed Rest (BR) and Partial Water Immersion (PWI) models simulate microgravity on the Earth and provoke prompt changes in the visco-elastic properties of the skeletal muscle. Visco-elastic properties of the muscle indeed are affected by the contraction (2, 3). Recently we have described upper trapezius (UT) and tibialis anterior (TA) muscles’ visco-elastic response to brief horizontal BR and PWI (4). Here we demonstrate differences in visco-elastic properties between relaxed and contracted state of the UT and TA muscles during PWI. Methods: Subjects: 18 healthy working-age females participated in study. Measurements: Frequency (Hz) and logarithmic decrement of damping mechanical oscillation and stiffness (N/m) from relaxed and contracted UT and TA muscles in PWI and in dry condition were recorded by myometric method (5) in a special ergotub. Results: Significant differences of the state of the UT in different conditions were detected individually; except for 1 person in relaxed and 2 people in contracted state of the TA, 4 people had non-significant difference in relaxed and 3 people in contracted state of UT. Due to large intra-individual variation, the differences are not statistically significant for the whole group. Discussion: Muscle’s visco-elasticity is related to third filament-system, particularly associated to stiffness and elasticity properties of the intra-sarcomere structures (6). Decrease in the amount of titin under microgravity substantially contributes to the so called hypogravity muscle syndrome (7). Understanding of Frank-Starling mechanism has recently been upgraded with an important role of myocardial elasticity (8), and the passive elasticity of the same titin filament-system provides the diaphragm with power of recoil (9). Registering the visco-elastic properties will enhance the understanding of the systemic elasticity of the musculoskeletal support system. This is in line with the tensegrity theory, which inter-relates the nano-, micro-, macro- and organ-system levels to structurally and functionally complete biological organism (10). As recently shown in orthopaedic rehabilitation (11), simply measuring the skeletal muscle quality (expressed by muscle visco-elastic properties) could be diagnostically as valuable as the characteristics of performance. Gathering information about skeletal muscle’s conditional behavior in supportlessness using myometric test could add relevant insight to existing measurements of the performance and other characteristics. We will further study skeletal muscle properties and performance in PWI combining myometry and underwater EMG with different loadings. 1. Miwa et al. Ageing reduces sympatho-suppressive response to head-out water immersion in humans. Acta Physiol Scand. 1996 2. Bizzini, Mannion. Reliability of a new, hand-held device for assessing skeletal muscle stiffness. Clinical Biomechanics 2003 3. Gavronski et al. Evaluation of viscoelastic parameters of the skeletal muscles in junior triathletes. Physiological Measurement 2007 4. Viir et al. Skeletal muscle tone characteristics in upright, supine and partial water immersion conditions. 57th IAC-06 Valencia A1.3.04 5. Vain. A method and device for recording mechanical oscillations in soft biological tissues, United States Patent No. 6132385, 2000 6. Lieber et al.Cytoskeletal disruption after eccentric contraction-induced muscle injury.Clin Orthop Relat Res. 2002 7. Vikhlyantev et al. Polymorphism of skeletal muscle titin under the extreme conditions of hibernation and microgravity: the diagnostic value of titin isoforms for choosing approaches to the correction of "hypogravity muscle syndrome". Dokl Biochem Biophys. 2006 8. Fukuda, Granzier. Role of the giant elastic protein titin in the Frank-Starling mechanism of the heart. Curr Vasc Pharmacol. 2004 9. Moore et al. Passive properties of the diaphragm in COPD. J Appl Physiol. 2006 10. Ingber. How cells (might) sense microgravity. FASEB J. 1999 11. Lamberg et al. Myotonometry to Detect Risk Factors after Tendon Transfers. International Meeting on Upper Limb in Tetraplegia September 17-20, 2007 Philadelphia, PA
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