PhD, Associate Professor R.V. Kuchin¹
Dr.Biol., Associate Professor M.V. Stogov¹
PhD, Associate Professor N.D. Nenenko¹
PhD, Associate Professor N.V. Chernitsyna¹
Associate Professor T.A. Maksimova^1
1Yugra State University, Khanty-Mansiysk

Keywords: bone mineral density, sports activities, climatic conditions, young women.

Introduction. Industrial development of the northern regions of the Russian Federation causes a significant influx of migrants who are generally poorly adapted to new climatic and geographical conditions. In comparison with other tissues of human body, bone tissue is characterized by slower adaptation to new environments.  Research has shown that migrants moving from south to north and their descendants have lower bone mineral density relating to the permanent residents of the region in question [1,6,9]. These observations correlate with other research papers that show that residents of northern European regions relative to those of southern regions demonstrate symptoms of bone mass loss more often and also have a higher frequency of limb bone fracture, with the trend more presented in females [4,7,11].

We believe that one of the generally accessible and large scale methods to prevent bone mass loss may be the increase in physical activity of migrants and their descendants. A large body of evidence in this respect suggests that sports activities boost mineral density of bone tissue, reduce incidence of osteopenia and osteoporosis, including that in adolescents and young women [2,3,5,15,17]. It is equally obvious that different kinds of sports may have varying effect on bone mass gain [8,12,14].

Thus, existing literature data give reason to believe that engaging in sports activities may represent a method to prevent bone mass loss in young women – descendants of migrants to the northern regions of Russia. Urgency of this research is also related to the fact that the issue of early bone mass loss in the first-generation descendants of newly arrived population is still largely unseen. However, as migratory flows continue to intensify, this problem could reach mass proportions soon enough.

Objective of this research was to assess bone tissue condition and adaptation of body systems in young females – descendants of migrants to the climatic and geographical conditions of the northern regions of the Russian Federation in the context of their athletic specializations.

Materials and methods. The base study included 60 young women who were born and permanently reside in the city of Khanty-Mansiysk. Köppen-Geiger climate classification — Dfc: snow climate, fully humid, cool summer and cold winter and T_min > −38°C [15].

Entry criteria for young women: age from 18 to 24, place of birth: KM, place of permanent residence: KM, first generation of migrants from the central part of the Russian Federation, ethnicity: Russian, 5–10^th day of menstrual cycle (follicular phase).

The entire cohort of the subjects included in the research was divided into four groups depending on the their physical activity and athletic specialization.

Group 1 (n=15) included young women who had not been engaged in regular sports activities. Average age – 20.2±0.5. Group 2 (n=15) included young women engaged in ski sports for 5–8 years. Average age – 20.0±1.2. Group 3 (n=15) included young women engaged in volleyball for 5–8 years. Average age – 20.6±1.0. Group 4 (n=15) included young women engaged in martial arts (judo) for 5–8 years. Average age – 20.8±0.5. Thus, all groups of subjects in the research were comparable in terms of age and length of involvement in athletic activities.

The experimental group (reference group, RG) included 15 young women who had not been engaged in regular sports activities and lived in the city of Tyumen. Köppen-Geiger climate classification – Dfb: snow climate, fully humid, warm summer and at least 4 T_mon≥ +10°C [15]. Average age of subjects in this group — 20.8±0.6.

The screening was based on the ethical principles of the Declaration of Helsinki wherein each subject submitted a signed voluntary informed consent for involvement in the research.

Bone Tissue Densitometry. The mineral density of skeleton segments was assessed using dual energy X-ray absorptiometry with the X-ray bone densitometer by GE Medical Systems Lunar Prodigy. The mineral density was measured in the lumbar part of the spine (L2-L4) and the proximal area of the femur.

Biochemical Examination. All subjects underwent biochemical examination of their blood serum. Blood serum was examined for calcium concentration (total and ionized calcium), activity of bone alkaline phosphatase, concentration of type I collagen carboxyterminal telopeptide, osteocalcin, calcitonin, parathyroid hormone, testosterone, estradiol, cortisone and 1,25(OH)₂D. The quantitative determination of bone turnover markers and hormones was performed using the ELISA test in the ELx808 reader by BIO-TEK Instruments Inc (USA) with the help of reagent kits by IDS (Immunodiagnosticsystems, UK), Nordic Bioscience Diagnostics (Denmark), DIAsource ImmunoAssays S.A. (Belgium). The concentration of total calcium and the activity of alkaline phosphatase, parathyroid hormone, testosterone, cortisone and estradiol was determined in the Beckmen&Coulter automatic analyzers (UniCel DхL 800 and DxC 800). Ionized calcium was assessed using the Ultra STP pHOxUltra blood gas/electrolyte analyzer.

Statistical Analysis. The obtained data are represented in tables as the arithmetic mean and the standard deviation (Xi±SD). Normality of the selections was determined using the Shapiro-Wilk test. Significance of differences in parameters between two groups was assessed depending on the normality of compared selections using either the parametric Student's t-test or the non-parametric Wilcoxon's W-test. Significance of multiple inter-group differences was determined using the Newman-Keuls test.

Results. Bone Tissue Densitometry. Research results have demonstrated that young women not engaged in sports and residing in KM (group 1) had an insignificantly lower mineral density in the examined skeleton segments relating to their counterparts of the same age from reference group (Table 1).

Biochemical Screening. Most serum parameters in group 1 subjects had differences in the central tendency values as compared to the reference group: higher concentration of carboxyterminal telopeptide, osteocalcin, parathyrin, bone alkaline phosphatase, estradiol and low level of active vitamin D (Table 2). Vitamin D levels in the blood serum in young group 1 women were on average 3.2 times lower (p<0.05) while the carboxyterminal telopeptide concentration was 1.7 times higher (p<0.05) than those in the reference group.

Analysis of metabolite level and bone-turnover regulators in young women residing at KM and engaged in sports revealed that group 2 subjects (skiing) had significantly higher levels of carboxyterminal telopeptide, osteocalcin, calcitonin and active vitamin D and a lower concentration of testosterone in blood serum (p<0.05) as compared to group 1 subjects. The last two parameters also had significant difference from average values in subjects from groups 3–4 (p<0.05). Group 3 subjects (volleyball) had significantly higher concentration of carboxyterminal telopeptide, osteocalcin, calcitonin in blood and lower level of cortisone (p<0.05) as compared to group 1. Group 4 subjects also had significantly higher levels of carboxyterminal telopeptide, osteocalcin and calcitonin (p<0.05) as compared to average values for group 1. In addition, concentration of calcitonin in blood serum in this group was significantly different from that in groups 2–3 (p<0.05).

The conducted research confirms our assumptions regarding female KM residents – first-generation descendants of migrants not engaged in sports. They have demonstrated symptoms of delay in bone mineralization relating to their counterparts residing in less severe climate. Due to this delay, young women not engaged in sports and reside at KM may fail to reach peak bone mass. Hence, early symptoms of osteopenia and osteoporosis may be expected to develop in female residents of the region.

The comparative study of obtained data gives us reason to believe that sports activities effectively help prevent these changes. Thus, groups of subjects engaged in sports (groups 2–4) had higher levels of carboxyterminal telopeptide, osteocalcin and calcitonin in blood serum as compared to the young women with usual physical activity levels (group 1). These parameters include both osteolysis and osteogenesis markers. We may assume that this attests to the highly active bone turnover which is quite possible in young women engaged in sports [10].

The observations below are related to the difference registered in subjects depending on their athletic specializations. Thus, group 2 subjects (skiing) demonstrated a significantly higher level of active vitamin D as compared to groups 3–4 which is to be expected as outdoor sports contribute to this [16]. Results for group 3 subjects (volleyball) were characterized by a lower level of stress hormone — cortisone — and a higher value of BMD.

Conclusion. Therefore, this research has demonstrated that young women – descendants of migrants not engaged in sports and permanently residing at KM have a delay in bone mineral uptake as compared to their counterparts engaged in sports and counterparts residing in middle latitudes. These changes are primarily caused by the low level of exposure to sunlight coupled with insufficient physical activity.

Increased physical activity demonstrated by young women engaged in various sports neutralizes the BMD abnormality found in young women with usual physical activity levels. Engagement in sports activities in a northern region results in anabolic phenomena in bone tissue, including via stimulation of mechanisms that regulate calcium turnover. Therefore, the osteotropic effect observed in young women engaged in sports proves that physical exercise can be used to prevent structural and functional changes in bone tissue seen in young women who are descendants of newly arrived population in northern regions of the Russian Federation. Moreover, volleyball may also be quite efficient for this cohort.

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Corresponding author: kuchin_r@mail.ru

Abstract

This research has tested a hypothesis regarding sports activities preventing disorders of bone mineralization in females in the conditions of the northern regions of Russia. The base study included young women aged 18–24 (the first generation of migrants from the central part of Russia) permanently residing in the city of Khanty-Mansiysk (Russia). Group 1 (n=15) included young women not engaged in regular sports activities. Group 2 (n=15) included young women practicing skiing. Group 3 (n=15) included young women engaged in volleyball. Group 4 (n=15) included young women engaged in judo. The reference group included 15 young women doing sports and living in the city of Tyumen (Russia). Group 1 subjects had symptoms of delay in bone mineral density (BMD) compared to their peers residing in less severe climate. Young women doing sports did not have these symptoms. Young female volleyball players had the highest BMD values. Young women – descendants of migrants doing sports permanently residing in the northern regions of Russia have no disorders of bone mineralization compared to their peers doing sports.