V.A. Klendar¹
Associate Professor, PhD N.A. Gross^1
1Federal Research Center of Physical Culture and Sport, Moscow

Keywords: children with impairments, heart rate variability, hemodynamics, adaptive responses.

Introduction. Improvement of motion coordination mechanisms along with high stability of vegetative reactions promoting homeostasis are essential for better understanding of motor functions as a factor that ensures the maintenance of vertical spatial stability.

Rehabilitation by means of exercise therapy requires physical loads to be adequate to the age of sick children, their capabilities and physical fitness level.

Heart rate variability (HRV) analysis is a non-invasive method of assessing the conditionality of the autonomic nervous system (ANS) divisions and bodily adaptation resources. Therefore, the implementation and application of this method is beneficial for the bodily functionality and functional reserve rating in application to the children diagnosed with infantile cerebral palsy (ICP).

The heart rate variability analysis application to profile the age- and gender-specific variations in the functional adaptation of the children with motor disorders gives the means to individualize the adaptation process design to effectively control and prevent disadaptation conditions.

Objective of the study was to identify the peculiarities of the state of adaptation mechanisms in the children with ICP during spatial postural control.

Methods and structure of the study. Orthostatic test is one of the simplest and most informative functional tests used to rate the reserve capacities of the body’s regulation systems. The study applied the heart rate variability analysis to estimate relative spectral indices (HF,%, LF,%, VLF,%) and stress index (SI), which reflects the degree of centralization of heart rhythm and heart rate control.

The study of hemodynamic reactivity in the children with impairments involved the group of children (n=22) aged 2-15 years diagnosed with ICP of different forms. The ECG-signal was registered in the prone position in the II standard lead using the diagnostic device "Varicard 2.51”. ECG was registered in the supine (horizontal) position and during orthostasis, for 5 min in each position. The active orthostatic test was used as a functional test. During the examination, the children were divided into 3 groups based on age periodization: under 3 years old, 4-7 years old, 8-15 years old; gender type (nG=13, nW=7) and type of autonomic nervous regulation (ANR) of the vegetative state: parasympathetic - at LF/HF < 0.5; balanced – at 0.5 < LF/HF < 1; sympathetic - at LF/HF > 1.0.

Results and discussion. Based on the heart rhythm response to the orthostatic test and spectral indices of HRV in the three study groups, the children’s functional state and adaptive reserves were assessed (Table 1).

Table 1. Changes in spectral indices of HRV in children with ICP from three age groups during orthostatic test.

It is the sympathetic and neurohumoral responses that prevail in the picture of the initial adaptive response rates affecting the heart rhythm of the children with impairments from two age groups (under 3 and 4-7 y.o.).

In the age group of 8-15, it was the sympathico-parasympathetic impact that was more pronounced at the low values of neurohumoral regulation, that is, it was the autonomous adaptive mechanisms that had the predominant regulatory influence, which can be explained by the onset of puberty in this age period.

Therefore, the vegetative regulation of the initial state at rest in the supine position in all age groups of children with impairments is generally characterized by decreased parasympathetic influence and increased tone of the sympathetic division of the ANS.

Increasing values of vagal influence and vasomotor center during orthostasis against decreasing regulatory influence of the central structures testifies to the adequacy of the adaptive response of the innate adaptation mechanisms in this age period (under 3 y.o.), and the predominance of the sympathico-humoral type of regulation indicates the low adaptive reserve and energy deficient state.

In the age group of 4-7, we also observed increasing values of vagal influence and vasomotor center against decreasing regulatory influence of the central structures, which is indicative of the adequate response of the innate adaptation mechanisms in this age period and its reserve available.

In the children of 8-15 years of age, the drastic changes towards the decrease in the values of vagal and neurohumoral heart rate regulation during orthostasis indicate the failure of adaptive responses, as evidenced by significant activation of the central mechanisms of regulation, which also testifies to a hyperadaptive reaction.

The determining influence of the sympathetic and central regulatory mechanisms on the body position in the age group under 3 may be indicative of the immaturity of the mechanisms of regulation, and in the age group of 8-15 – of the depletion of adaptation mechanisms. The indices of reactivity of the adaptation mechanisms to the orthostatic test in the older age group of children with ICP proves the presence of energy-deficient states, which corresponds to the decrease of adaptive reserves at this age.

The general age tendency in the spectral characteristics during the orthostatic test is characterized by the shift of the regulatory influence of the autonomous centres (vagal and vasomotor) on the central (neurohumoral) one. This shift is due to the depletion of the protective adaptative-trophic effect of the vagus nerve, which manifests itself as decreased stress tolerance and determines the energy deficient state, associated with hypokinesia, which increases with age. Wherein, it is the central structures of the CNS that take on the role of hemodynamic change regulator. The dynamics of disregulatory manifestations is due to age increment and reduced motor load.

The spectral characteristic values that reflect the overall reactivity of the adaptation mechanisms, are decreased or inadequately high as compared to those in healthy children in the same age periods.

There are gender differences in response to the orthostatic test. They reduplicate the inadequate type of response to orthostasis in children with motor disorders – increasing sympathico-parasympathetic responses and are characterized by reduced neurohumoral influence - manifestation of energy deficiency. In boys changing their body position, it is the sympathetic mechanisms with the predominance of the central ones that are determining, in girls - autonomous. The state of reactivity of adaptation mechanisms to a changing body position is more advanced in girls (Table 2).

Table 2. Spectral indices in children with ICP during orthostasis.

During the HRV analysis, 20 children of 3-15 years of age diagnosed with ICP, who had different types of predominating autonomic nervous regulation, were observed to demonstrate different mechanisms of activation of the regulatory systems in response to the orthostatic test, as presented in Table 3.

Table 3. HRV spectral analysis indices in 3-15-year-old children with ICP with different types of ANR in response to orthostasis

Legend: 1(V) – vagotonic type of ANR; 2(N) – normotonic; 3(S) – sympathicotonic.

Conclusion. The HRV analysis has enabled to detect the changes in the heart rhythm frequency components and make quantitative evaluation of their effect on the rhythm dynamics.

The sympathicotonics demonstrated an atypical reaction with an increasing vagotonic influence, activation of the vasomotor centre and a reduced ergotropic influence, which indicates the failure of adaptive reactions by hypoergic type.

The children with predominating sympathetic nerve effects on the heart rhythm and influence of the central structure regulators are characterized by reduced adaptive capabilities of the body. The sympathetic type of reactivity, which is the most unfavorable adaptive type, is marked by an atypical response to orthostasis.

The fact that the ICP children demonstrate the base normotonic and vagotonic types of response to external stress stimulation does not mean that they have the expected balanced adaptive response, although the original vegetative status is a genetically determined and constant physiological state.

The altered reactivity to the orthostatic test in the children with ICP, even where physiologically effective types of ANR are present, is due to motor responsiveness sagging, which, with age, results in asthenization of the nervous system, imbalances of the higher vegetative centres functionality and poor physical fitness. All this results in the negative changes in responsiveness rates and the growing inefficiency of adaptive responses.

References

1. Berseneva I.A. Otsenka adaptatsionnykh vozmozhnostey organizma u shkolnikov na osnove analiza variabelnosti serdechnogo ritma v pokoe i pri ortostaticheskoy probe. Avtoref. dis. kand. biol. nauk [Estimation of adaptive capabilities of schoolchildren based on analysis of heart rate variability at rest and during orthostatic test. PhD Diss. abstr.], 2000, 22 p.
2. Goncharova G.A., Gross N.A., Berkutova I.Y. Otsenka stepeni adaptatsii fiziologicheskikh mekhanizmov organizma u detey-invalidov pri fizicheskikh nagruzkakh [Evaluation of physiological adaptation mechanisms in children with disabilities during exercise]. Vestnik sportivnoy nauki, 2014, no. 6, pp. 46-48.
3. Klendar V.A., Gross N.A. Osobennosti vegetativnoy regulyatsii serdechnogo ritma u detey s NODA, pri primenenii metodov fizicheskoy reabilitatsii s dvigatelnymi rezhimami raznoy napravlennosti [Features of autonomic regulation of heart rate in children with locomotor system disorders in application of methods of physical rehabilitation with multi-purpose motor modes]. Vestnik sportivnoy nauki, 2015, no. 2, pp. 41-45.

Corresponding author: info@vniifk.ru

Abstract

The study applied the heart rate variability analysis as non-invasive method to rate the autonomic nervous system conditionality and bodily adaptation resources, and demonstrated the method being beneficial for the bodily functionality and functional reserve rating in application to the children diagnosed with infantile cerebral palsy (ICP). The HR variability analysis application to profile the age- and gender-specific variations in the functional adaptation of the children with motor disorders give the means to individualize the adaptation process design to effectively control and prevent disadaptation conditions.

Furthermore, the HR variability analysis in application to the ICP children’s spatial postural control studies provided data on different elements of the regulator mechanisms and general adaptation responses. The motor responsiveness sagging with age was found to result in imbalances of the higher vegetative centres functionality and poor physical fitness as verified by the negative changes in responsiveness rates and the growing inefficiency of adaptive responses.