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Role of axial and support unloading in development of hypogravitational motor syndrome

Elena S. Tomilovskaya1*, Ilya V. Rukavishnikov1, Tatiana A. Shigueva1, Tatyana B. Kukoba1, Inna S. Sosnina1, Lyubov E. Amirova1 and Inessa B. Kozlovskaya1
  • 1 Institute of Biomedical Problems (RAS), Russia

Dry Immersion (DI) studies that were performed for years at the Institute of Biomedical Problems have shown that support withdrawal is followed by the development of hypogravitational motor syndrome signs (HMS), similar to those observed after space flights: postural muscle atonia and atrophy, hyperreflexia of spinal reflexes, voluntary movement discoordination, postural and locomotor alterations, back pain etc. (Kozlovskaya et al., 1988; 2007; Miller et al., 2004; Shenkman et al., 2017). Daily mechanical stimulation of the soles during DI eliminates the mentioned effects almost to full extent (Grigoriev et al., 2004; Kozlovskaya et al., 2007). Basing on these results it was concluded that support afferentation plays the role of trigger in development of HMS. However it is necessary to take into account that withdrawal of weight in weightlessness and DI is followed not only by supportlessness but also by axial unloading. So the aim of this work was to study the effects of supportlessness coupled with axial loading to define the role of axial load on HMS development. Twenty healthy volunteers divided into 2 groups took part in the study. No influences except 5-days DI was used in the group which served as a control. The subjects of experimental group in DI every day for 4 hours were wearing "Penguin" axial loading suit that provided the 16-18 kg axial load on the body – from the shoulders to the ankles. Parameters of the postural and locomotor activities, the spinal stretch reflexes, the accuracy of voluntary movements, intervertebral discs height, back pain intensity, tone and force-velocity properties of leg and back muscles have been studied. All the mentioned signs of HMS were observed in the control group: the tone of postural muscles sharply decreased, hypereflexia of stretch reflexes was observed, muscle strength and endurance decreased, postural stability was altered, voluntary movement coordination declined. Results of the experiments confirmed our previous suggestion that muscular atonia provides the development of movement disorders, back pain and other phenomena such as increase of height, elongation of the spine and height of intervertebral disks, etc. (Rukavishnikov et al., 2016; Treffel et al., 2016). Back extensor muscles atonia and significant increase in the intervertebral disk height were registered in the lumbar spine projection; at the same localization all test subjects reported the symptoms of back pain. In the experimental group the intensity of back pain was significantly lower (p=0.0028 for DI1, p=0.006 for DI2 and p=0.0004 for DI3 – by ANOVA repeated measures with Bonferroni correction) (Fig.1). Figure 1. Back pain intensity in the course of Dry Immersion in 2 groups. * - significant difference compared to the baseline; @ - significant difference between groups (p<0.01). Height increase and the decline of force-velocity properties of back and neck muscles were also significantly lower than in the group without countermeasures (p<0.05). However for the leg muscles the changes were similar to the control group. Spinal reflex facilitation (Fig.2), accuracy of hand voluntary movements’ decrease and other HMS signs were not significant in this group. Slight tendency to H-reflex threshold decrease was registered in this group, however the changes were not significant (p=0.062). Figure 2. Changes of spinal reflex characteristics in 2 groups in the course of Dry Immesion. A – Changes in the threshold of H-reflex; B – Changes in peak amplitude of H-response. Blue lines – the group of “pure” immersion with no countermeasures; red dotted lines – the group of 4 hours daily axial loading in the course of Dry immersion. * - p<0.05 compared to baseline values; @ - significant difference between group (p<0.05). There were not revealed significant difference between groups in parameters of postural and locomotor coordination. The results of the study have shown that axial unloading in microgravity plays significant role in development of HMS. However it reveals more tight connections of avail loading to muscles of the body when the support reactions are involved to a great extent in the control of leg muscles state and locomotor and postural functions.

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Acknowledgements

The study is supported by RFBR № 16-29-08320-OFI-m.

References

1. Grigoriev, A.I., Kozlovskaya, I.B., and Shenkman, B.S. (2004). Role of support afferentation in organizing the tonic muscular system. Russian physiology J. by I.M. Sechenov. 5, 508-521. 2. Kozlovskaya, I., Dmitrieva, I., Grigorieva, L. et al. (1988). Gravitational mechanisms in the motor system. Studies in real and simulated weightlessness. In: Stance and Motion. Eds. V.S. Gurfinkel, M. Ye. Ioffe. J. Massion Plenum. New York, 37-48. 3. Kozlovskaya, I.B., Sayenko, I.V., Sayenko, D.G. et al. (2007). Role of support afferentation in control of the tonic muscle activity. Acta Astronaut. 60, 285–294. 4. Miller, T.F., Saenko, I.V., Popov, D.V. et al. (2004). Effect of mechanical stimulation of the support zones of soles on the muscle stiffness in 7-day dry immersion. J. Gravit. Physiol. 11, 135–136. 5. Rukavishnikov, I.V., Amirova, L.E., Kukoba, T.B., Tomilovskaya, E.S., Kozlovskaya, I.B. (2017). Effects of gravitational unloading on back muscles tone. Human Physiology, 43:3, 291-300. 6. Shenkman, B.S., Grigoriev, A.I., Kozlovskaya, I.B. (2017). Gravity mechanisms in tonic motor system. Neurophysiological and muscle aspects. Human Physiology. 43, 5: 578-590. 7. Treffel, L., Mkhitaryan, K., Gellee, S., Gauquelin-Koch, G., Gharib, C., Blanc, S., Millet, C. (2016). Intervertebral disc swelling demonstrated by 3D and water content magnetic resonance analyses after a 3-day dry immersion simulating microgravity. Front. Physiol. 7: 605.

Keywords: dry immersion, hypogravitational motor syndrome, Back Pain, axial loading, support unloading, H-Reflex, microgravity

Conference: 39th ISGP Meeting & ESA Life Sciences Meeting, Noordwijk, Netherlands, 18 Jun - 22 Jun, 2018.

Presentation Type: Extended abstract

Topic: Bones and Muscles

Citation: Tomilovskaya ES, Rukavishnikov IV, Shigueva TA, Kukoba TB, Sosnina IS, Amirova LE and Kozlovskaya IB (2019). Role of axial and support unloading in development of hypogravitational motor syndrome. Front. Physiol. Conference Abstract: 39th ISGP Meeting & ESA Life Sciences Meeting. doi: 10.3389/conf.fphys.2018.26.00019

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Received: 02 Dec 2018; Published Online: 16 Jan 2019.

* Correspondence: Dr. Elena S Tomilovskaya, Institute of Biomedical Problems (RAS), Moscow, Russia, finegold@yandex.ru