Skeletal muscle tone characteristics in upright, supine and partial water immersion conditions
- Paper number
IAC-06-A1.3.04
- Author
Dr. Ragnar Viir, Rheumatism Foundation Hospital, Finland
- Coauthor
Dr. Arved Vain, Estonia
- Coauthor
Dr. Ahti Virkus, Finland
- Coauthor
Ms. Anne Selart, Student, Estonia
- Coauthor
Ms. Kristiina Rajaleid, Student, Sweden
- Year
2006
- Abstract
Introduction. Elimination of gravitational loading in longitudinal direction is key approach in horizontal or head-down bed rest studies. However, the gravitational force still acts on the subject in the horizontal plane. In water immersion (WI) model the loading differential is eliminated and the support function is distributed homogeneously. The goal of this paper is to investigate the difference of relaxed muscle tone characteristics between the standing (ST), sitting (SI), supine rest position (SR) and while being horizontal in partial posterior neck level thermo-neutral water immersion (PWI), and to discuss the results for WI and sedentary life studies. Method. Upper Trapezius (UT) muscle tone (the natural oscillation frequency at relaxation (FREQ) [Hz]), stiffness (STIFF) [N/m] and elasticity (reciprocal of logarithmic decrement of dampening, DECR) in ST, SI, SR, PWI and Tibialis Anterior (TA) muscle FREQ, STIFF and DECR in SR and PWI measures from 15 women were recorded by myometric method (Vain, U S Patent No. 6,132,385). This non-invasive method induces and then records oscillation of the muscle tissue by a short mechanical impact with minimal energy, avoiding neural and non-elastic reactions. Results. No significant difference was detected between ST and SI, but change from upright to SR diminished UT FREQ 33.33 % and STIFF 42.12 %, while DECR did not change. Changing from SR to PWI, UT FREQ decrease 3.12 %, DECR increased 24.25 % and STIFF decreased 3.72%, while TA muscle FREQ decreased 5.53 %, DECR increased 12.57% and STIFF decreased 9.72%. Discussion. We observed a significant quantitative decrease in FREQ and STIFF of UT muscle as a result of unloading of muscular support function, while going from upright to supine rest position. Further, the decrease of tone, stiffness and elasticity (increase of logarithmic decrement of dampening) is more pronounced in partial water immersion than in supine rest condition. These results are in line with classic weightlessness studies of the correlation between the skeletal muscle tone decrease and various degree of support elimination like immersion and bed rest. Our results and study approach might also give insights for better understanding the role of sitting immobility and cumulative monotonous support function loading of skeletal muscle in daily sedentary life.
- Abstract document
- Manuscript document
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