Dr.Biol., Professor O.L. Nifontova¹
Dr.Biol., Associate Professor A.A. Govorukhina¹
Dr.Med., Professor O.A. Malkov¹
Dr.Biol., Professor O.G. Litovchenko²
Postgraduate V.Z. Konkov^1
1Surgut State Pedagogical University, Surgut
²Surgut State University, Surgut

Keywords: schoolchildren, physical development, cross-country skiing.

Background. Children's physical development rate is commonly considered one of the key criteria of children's population health affected by a variety of internal and external growth factors. Adaptation mechanisms of the young population living in the extreme Russian Yugra Far North conditions are exposed to the climate-specific stressors [5]. Children and adolescents are naturally most vulnerable to such stressors due to the morphological and functional transformation processes in their organs and body systems being still in progress [2].

It is cross-country skiing that is one of the most popular and accessible sport disciplines for both the adolescent and junior population in the Russian Far North [6]. In the studies of the underage body adaptability to athletic training under the extreme conditions of the Russian Yugra Far North the authors have long given a high priority due to the effects of the environment-specific stressors affecting every physiological system.

Objective of the study was to profile the 9-11 year-old schoolchildren’s physical progress rates versus their progress in cross-country skiing.

Methods and structure of the study. Subject to the study were 110 boys of 9-11 years of age residing in the Russian Yugra Far North and split up into the following 6 groups: (1) 9 year-old beginner skiers in their first training year (n=17); (2) 10 year-old skiers in the second training year (n=19); (3) 11 year-old skiers in the third training year (n=20); and (4, 5, 6) reference groups of 9, 10 and 11 year-old non-sporting peers (n=24, n=15, n=15), respectively. The study was performed at the end of the training year (March-April) at the health offices of the Surgut regional sport schools with the following standard and common tests being applied: key anthropometric measurements to obtain body length (BL), body mass (BM) and chest circumference (CC) indices; body surface area (S) indices; Quetelet body mass (mass/length) indices (KI); sthenia indices (SI) and Pignet indices (PI). The test data were analysed using the standard Microsoft Excel 2007 spreadsheets and STATISTICA 10.0 software toolkit. The data distribution normality was checked using the Shapiro-Wilk test. The normally distributed data arrays were tested by the Student’s t-distribution parametric data test of independent samples; and the abnormally distributed data arrays were subject to the Mann-Whitney non-parametric test. The data differences were rated as significant if р<0.05/ 0.01/ 0.001.

Study results and discussion. The subjects’ physical development process was rated by the key anthropometric data including BL, BM and CC, with the comparative data given in Table 1 hereunder.

Body length (BL) is considered a key characteristic of the bodily growth process and somatic maturity level [3]. It is common knowledge that boys come to the first growth leap being 4-5 years of age with the growth pace then falling to reach its minimum at the age of 9 followed by a steady growth period till 13. Since the 8^th year, the yearly BL increment normally averages some 5 cm/year [1]. The subject 9-11 year-old boys’ growth variation analysis showed each of the group falling within the age-specific physiological norm [1]. The maximal body length increment of 5.82 cm/year was found in the 11 year-old sporting subjects versus the 6.55 cm/year increment in the 10 year-old non-sporting peers (p=0.004). The study found statistically significant intergroup differences in the 11 year-old subjects, with the sporting subjects’ body length estimated to exceed that of the non-sporting ones by 4.83 cm (p=0.032).

Table 1. Anthropometrics of the 9-11 year-old boys residing in the Russian Yugra Far North (M±σ)

*Sporting versus non-sporting subjects’ test data difference is significant if p<0.05 hereinafter

By the body mass (BM) indices (considered the most labile being dependent on a wide variety of factors [5]), the group of 11 year-old racing skiers was tested to exceed the norm by 1.65 kg [1] versus all the other groups that were within the norm. The normal BM yearly increment in the 5-12 year-olds is known to make up 3 kg/year [1]. Our tests showed the following BM yearly increments in the subjects: 1.86 kg/year and 3.99 kg/year in the non-sporting 10 and 11 year-olds, respectively; versus 1.31 kg/year and 8.71 kg/year in the 10 and 11 year-old racing skiers, respectively (p=0.004).

The chest circumference (CC) rating tests showed some excess of the age-specific norm both in the 11 year-old sporting and 9/11 year-old non-sporting subjects [1]. Furthermore, the sporting subjects were tested with the highest yearly increment of the inhale/ exhale/ resting CC in the 11 year-old subjects making up 7.09 cm/year, 7.71 cm/year (p=0.001) and 8.24 cm/year (p=0.001), respectively; versus their non-sporting peers tested with the insignificant CC increments under 3 cm/year. Furthermore, we found the statistically significant intergroup differences (p=0.025) in the exhale CC in the 10 year-olds with the highest rates found in the non-sporting ones. It is a common knowledge that the BL/BM anthropometrical measurements provide fairly accurate characteristics of the environment-specific body morphology types [4]. We found the Quetelet indices (QI) growth with age both in the sporting and non-sporting subjects in correlation with the natural body specific mass growth profile [7]. The QI in the 9-11 sporting year-olds was tested to grow by 53.97 g/cm (p=0.001) versus 30.6 g/cm in the non-sporting peers (p=0.016): see Table 2.

The Pignet index is a characteristic of the body growth proportionality and one or another body type [4]. Our tests showed the PI variations being age-unspecific and indicative of the week body type dominating in every group (both sporting and non-sporting) under the study. It should be noted that the sporting subjects were tested with the highest variations of the PI, with the PI growth in the 9 sporting year-olds found significant (p=0.024).

Table 2. Physical development rates of the 9-11 year-old boys residing in the Russian Yugra North (M±σ)

Note: 1) parametric Student’s t-criterion, M±σ; 2) non-parametric Mann-Whitney criterion, Md (Q₁-Q₃).

The sthenia indices (SI) were applied to profile the growth processes in the subjects. Every group was classified with the mesomorphic body type based on these indices. The sthenia indices showed a significant drop by the age of 11 both in the sporting (p=0.001) and non-sporting groups (p=0.035), the finding being indicative of a growing pace of the transversal growth processes.

Having analysed the body surface (S) rates, we found the growth of the S rates with age being within the norm and making up by 0.2 m² in the sporting 9-11 year-olds (p<0,001) versus 0.12 m² in their non-sporting peers (p=0.002).

Conclusion. Having analysed the physical development rates of the 9-11 year-old boys residing in the Russian Yugra Far North we found the aggregate physicality of both the racing skiers and non-sporting subjects being on the rise. The study found that the non-sporting schoolchildren showed the first signs of the “growth leap” by the age of 10 versus their sporting peers who were one year later in this aspect (11 years of age). This finding may be explained by the effect of physical load. The physical development indices showed domination of the weak body types in every group, with some dominance of the mesomorphic body type and some distortion of the growth processes in favour of the transversal body dimensions.

References

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Corresponding author: physical_science@surgpu.ru

Abstract

The study analysed the physical development rates of 9-11 year-old male residents (n=110) of the Russian Yugra North versus their track records in cross country skiing. The subjects were split up into the following six groups: (1) 9 year old beginner (first-year) ski racers; (2) 10 year old second-year ski racers; (3) 11 year old third-year racing skiers; and (4, 5, 6) three reference groups of the 9, 10 and 11 year old non-sporting peers. The study found that the non-sporting schoolchildren showed the first signs of the “growth leap” by the age of 10 versus their sporting peers who were one year later in this aspect (11 years of age). This finding may be explained by the effect of physical load. The physical development indices showed domination of the weak body types in every group, with some dominance of the mesomorphic body type and some distortion of the growth processes in favour of the transversal body dimensions.