Dr.Hab., Professor D.V. Syshko¹
PhD, Associate Professor Z.N. Zevreeva¹
PhD M.N. Klemparskaya¹
E.V. Perekotiy^1
1V.I. Vernadsky Crimean Federal University, Simferopol

Keywords: hearing impairments, body balance, stabilography, vestibular stressors, center of body mass.

Introduction. There is a symbiotic relationship between the auditory analyzer and motor function. Auditory deprivation causes the vestibular and motor sensory systems malfunction, which affects the bodily coordination and balancing abilities. Body balance is associated with realization of the motor function, coordination abilities and spatiotemporal perception [5]. There is evidence for the peculiarities of vegetative reaction in the deaf while they maintain their postures and body balance [7]. Therefore, the research data on biomechanical indicators of body balance in hearing impaired children are relevant from the standpoint of both fundamental and applied science. Body balance is a generalized criterion for assessing man’s functional state, in hearing impaired people in particular. Consideration of the body balance characteristics while evaluating man’s functional state will help improve the process of adaptation of the sensory systems that provide movement coordination [4]. The peculiarities of functioning of the sensory systems and compensations predetermine the peculiarities of the motor sphere of children diagnosed with various disorders in the system of analyzers, in particular, the auditory one, and require a differentiated approach to the selection of informative research methods. Stabilometry is one of such methods for objective characterization of body balance [6]. This method is used to detect shifting of the center of body mass when exposed to a stabilometric test [3]. The body tremor features in an upright position, their determination and assessment are of particular value, both scientific and practical.

Objective of the study was to determine the effects of vestibular stressors on the body balancing ability in hearing impaired children.

Methods and structure of the study. Subject to the study were 10 boys – students of the boarding school for deaf and hearing impaired children, 1-3 types, all aged 13-14 years old (middle school age) and having different degrees of auditory deprivation. The body balance characteristics were tested in the following way: the subject was to remain upright on the stabilometric platform, after which his body balance indicators were recorded. During vestibular stimulation in a Barany chair, Voyachek test was carried out (10 rotations in 20 sec, head tilted forward at the angle of 30⁰, eyes closed, when the platform stopped the subject straightened his head and opened his eyes). The body balance characteristics were re-registered. The ST-150 complex (Moscow) was used during the experiment. The center of body mass, i.e. the center of pressure, on the plane of support and its shift, was recorded for 60 sec in each position - with open and closed eyes. These indicators were measured in the XY coordinate system. The following body balance characteristics were determined and processed: the area of statokinesiogram, S, mm2; the square of migratory oscillations of the pressure center - L, mm; the center of pressure movement area in the sagittal axis - Y, mm; the center of pressure movement area in the frontal axis - X, mm; energy costs for the postural control needs - A, J [3].

Results and discussion. Examination of hearing impaired children involves rather informative postural tests that help determine the features of the body balance control mechanisms, but they are generally aimed to evaluate the biological value of maintaining postural balance and cannot provide an accurate and qualitative assessment of the equilibrium function and functional state of the body. The analysis of biomechanical indicators in the orthograde posture gives a quantitative estimation of the degree of postural control violation. The indicators presented in Fig. 1 provide significant data on the body balance biomechanics. The study of the oscillations of the center of pressure in the hearing impaired children revealed that the indicators characterizing their body balancing ability in the orthograde posture, such as the area of ​​the statokinesiogram and the range of oscillations of the center of pressure in the frontal axis, changed significantly. The area of ​​statokinesiogram in the hearing impaired children decreased significantly (p≤0.05) under the influence of vestibular stressors - from 232.91+42.07 to 168.77+16.77 mm² with open eyes and from 208.82+44.53 to 189.92+40.96 mm² with closed ones, respectively. However, not all indicators changed statistically significantly after rotations in the Barany chair. It is known that the area of ​​ statokinesiogram (S) is defined as the area of ​​an ellipse that contains 90 or 95% of all points of square of migratory oscillations of the pressure center [1]. Consequently, the decrease of this indicator testifies to the economization of body balancing in children with auditory deprivation after vestibular stimulation. The detected phenomenon of this apparently paradoxical response to vestibular stressors in the hearing impaired children is of great academic interest. However, to some extent, these data compare favorably to the previously obtained data on the vestibulovegetative reactions in hearing impaired children. It has been established that, in contrast to hearing children, the central haemodynamic indices in hearing impaired children change insignificantly after vestibular stimulation [7].

Fig. 1.  Square (range) of migratory oscillations of pressure center in sagittal and frontal axis before and after vestibular stimulation in hearing impaired children

It should be noted that the square of migratory oscillations of the center of pressure after vestibular stimulation, both with open and closed eyes, did not change significantly. The center of pressure movement area in the sagittal axis also did not change significantly after vestibular stimulation, neither with open nor closed eyes. There were statistically significant changes in the center of pressure movement area in the frontal axis towards reduction (p≤0.05). Therefore, reduction in the area of ​​statokinesiogram in children under the influence of vestibular stressors was mainly due to the reduced movement area of the center of pressure in the frontal axis. This can be probably associated with the fact that rotations in the Barany chair during the Voyachek test, when the head is tilted forward, also occurs in the frontal axis. Therefore, adequately rated postural stimulants of the vestibular semicircular channels in the frontal axis were found to improve the static body balancing ability, since the area of statokinesiogram and center of pressure movement area in the frontal axis are reduced. However, data objectification requires understanding the biological "value" of this sustainability. In this view, it is the amount of energy spent on the migration of the pressure center in hearing impaired children after vestibular stimulation that is of interest (Fig. 2).

Fig. 2. Energy costs for body balance in children with hearing impairments in postural control tests

Thus, the energy cost A for the orthograde postural control in the children with hearing impairments prior to vestibular stimulations was 1.77±0.31 J with open eyes, and it amounted to 2.79±0.3 J (p≤0.05) after vestibular stimulation. While with closed eyes this indicator was equal to 1.39+0.23 J at rest, and 2.89±0.53 J after vestibular stimulation. Consequently, the data obtained suggest that static balance maintenance in children with auditory deprivations after vestibular stimulation requires more energy for muscle tone redistribution. However, the biomechanic rates of the postural balancing ability increase, since the area of ​​statokinesiogram (S, mm²) decreases in a similar manner to the center of pressure movement area in the frontal axis (X, mm). Adequately rated postural stimulants of the vestibular semicircular channels in the frontal axis were found to improve the static body balancing ability albeit associated with extra energy costs for the postural control needs. The study findings compare favorably to the data obtained by R.I. Danilova [2], according to which the proprioceptive sensory system functionality is a compensatory mechanism for maintaining body balance in children with hearing impairments. This gives grounds for using such stimuli and stressors for optimization of the vestibular and proprioceptive analyzer systems activity in children with hearing impairments. In turn, this optimization can be considered as a factor to expand the adaptation potential of children with auditory deprivations.

Conclusions:

1. The body balance indicators in children with hearing impairments after vestibular stimulation vary depending on the axis of the stimulant of the semicircular channels with the body mass movement area reduced in the frontal axis (p≤0.05) and with the area of statokinesiogram reduced as well (p≤0.05).
2. The postural control test using vestibular stressors leads to the improvement of biomechanical indicators of static stability in hearing impaired children.
3. Adequately rated postural stimulants of the vestibular semicircular channels in the frontal axis were found to improve the static body balancing ability albeit associated with extra energy costs for the postural control needs (p≤0.05).
4. Vestibular analyzer stimuli and stressors optimize the activity of the vestibular and proprioceptive analyzer systems, which expands the adaptation potential of children with hearing impairments.

References

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Corresponding author: syshko@list.ru

Abstract

The study was designed to test postural control ability in children with hearing impairments. The orthograde balancing ability was rated prior to and after the postural control tests in the 13-14 year-old boys (n=10) with auditory impairments. The body balancing ability in the sample was found to vary depending on the axis of the stimulant of the semicircular channels with body mass movement area reduced in the frontal axis (pЈ0.05), and with the square of migratory oscillations reduced as well (pЈ0.05). The postural balance irritant was found to facilitate the biomechanic rates of the postural balancing ability being optimized in the sample. Adequately rated postural stimulants of the vestibular semicircular channels in the frontal axis were found to improve the static body balancing ability albeit associated with extra energy costs for the postural control needs (with pЈ0.05).