PhD Elżbieta Huk-Wieliczuk
Jozef Pilsudski University of Physical Education in Warsaw, Warsaw
Faculty of Physical Education and Health in Biala Podlaska, Poland

Corresponding author: fizkult@teoriya.ru

Abstract 

An excessive volume and intensity of physical effort which takes place during sports training, and many years of playing career are not protected against the development of osteoporosis.

Objective of the study was to assess the current bone mineral density in female professional volleyball players and the intake of selected dietary components, compared with women not practising sport. 

Research methods and structure. The study included 40 female students from the University of Physical Education in Biala Podlaska. Bone mineral density (BMD) was determined in the humerus and in the whole skeleton using Dual Energy X-ray Absorptiometry (DEXA) method. The study was carried out using the HORIZON Ci device (USA). Using this device basic anthropometric indicators were measured: body weight (kg), body height (cm), Body Mass Index in kg/m²   and fat tissue content in %. Nutritional assessment was made on the basis of three diet-related interviews, each of which focused on a period of 24 hours (two working days and one day off). Most portions that were consumed were verified with the use of “Products and meals photo album” prepared by the National Food and Nutrition Institute in Warsaw. The amounts of proteins, calcium,  phosphorus, magnesium and vitamin D in daily food rations were calculated with “Dieta.5.0” software (NFNI). The obtained results were compared with the nutritional norms [7]  taking into account age, gender and physical activity. The norm at the level of estimated average requirement (EAR) was applied for all the analysed nutrients except vitamin D (according to nutritional recommendations, the norm at the level of adequate intake (AI) was used).

Results and conclusions. The presented study provides evidence for positive effect of physical activity on bone tissue metabolism in junior female professional volleyball players. It is recommended to constantly monitor bone parameters of junior female athletes in the period of reaching their peak bone mass is advisable in terms of prevention of osteoporosis as female athletes are at increased risk of this disease. Such a monitoring should be multifaceted, taking into account the nutrition model and hormonal diagnosis.

Keywords: female volleyball players, BMD, dietary factors.

Introduction.  Osteoporosis has been considered by the WHO as a civilisation disease, and defined as an ‘epidemic of the 21st century’. It is a systemic skeletal disease characterized by the loss of bone mass and its disrupted architecture. It has a latent course and its clinical symptoms are most often manifested in the form of increased bone fragility and an increased risk of fractures [1, 2].  Many scientific studies demonstrate a number of osteoporosis risk factors, including those modifiable, which are associated with life style [3, 4].  Physical effort is one of its elements. Regular physical activity with a training load undertaken in childhood and during the period of adolescence improves the metabolic profile, decreases the risk of obesity, improves the functioning of the cardiovascular system, and prevents the development of diabetes [5, 6]. In addition, it exerts an effect on bone mineral density. However, females who are highly active physically are not protected against the occurrence of cardiovascular diseases, or disorders of bone tissue metabolism, compared to those who undertake moderate exercises. This situation is due to an excessive volume and intensity of physical effort which takes place during sports training, and many years of playing career.

Objective of the study was to assess the current mineral bone density (the whole skeleton, the right and left humerus) in players professionally training volleyball, and consumption of the selected dietary components, compared to women who do not practice sports.  

Research methods and structure. The study included 20 female students from the University of Physical Education who professionally trained volleyball, aged 19-21. The training period in the examined female athletes was 7.713.85. The players trained 5 days a week, on average (5.360.48), and their weekly training load was 9.573.08 hours. The control group were women who were not highly active physically (students of cosmetology from the University in Biała Podlaska). The women were informed of the objectives and  methodology also how the survey was conducted. The participation was voluntary and the participants could withdraw from the experiment at any time. All procedures were approved by the Ethics  Committee for Scientific Research at Jozef Pilsudski University of Physical Education in Warsaw. Bone mineral density (BMD) was  determined in the humerus and in the whole skeleton using Dual Energy X-ray Absorptiometry (DEXA) method. The study was carried out using the HORIZON Ci device (USA). Using this device basic anthropometric indicators were measured: body weight (kg), body height (cm), Body Mass Index in kg/m²   and fat tissue content in %. Nutritional assessment was made on the basis of three diet-related interviews, each of which focused on a period of 24 hours (two working days and one day off). Most portions that were consumed were verified with the use of “Products and meals photo album” prepared by the National Food and Nutrition Institute in Warsaw. The amounts of proteins, calcium,  phosphorus, magnesium and vitamin D in daily food rations were calculated with “Dieta.5.0” software (NFNI). The obtained results were compared with the nutritional norms [7]  taking into account age, gender and physical activity. The norm at the level of estimated average requirement (EAR) was applied for all the analysed nutrients except vitamin D (according to nutritional recommendations, the norm at the level of adequate intake (AI) was used). The presented work includes initial results of research realised within the scientific project titled “Assessment of bone parameters in women practising different sports”, which was approved by the Ethics Committee for Scientific Research at Jozef Pilsudski University of Physical Education in Warsaw. Statistical analysis was performed with the use of one-way ANOVA, where the level of significance was set at p < 0.05.

Results. Table 1 presents anthropometric characteristics of the examined females. It was found that the mean body weight was considerably higher in volleyball players (66.17 kg), compared to the non-training group (62.5 kg) – by 5.9 %. However, an opposite relationship was noted taking into account the BMI. The examined females from both groups were characterized by age-appropriate amount of body fat, with its higher percentage observed in non-training women.

Table 1. Somatic characteristics of female athletes and controls

Table 2. Bone mineral density (BMD) in female volleyball players and controls.

Table 3.  Selected  nutrients in  daily food rations  of female athletes and controls  

* mean percentage of realisation of the norm at the level of estimated average requirement (EAR) and level of adequate intake (AI) for the group are given in brackets.

Discussion. Physical activity properly adjusted from the aspect of its form and intensity, pursued with the maintenance of dietary recommendations, prevents the loss of BMD and in this way reduces the risk of bone fractures. Various types of physical exercises exert a different effect on the bone remodelling [8]. Sports involving impact loading, including gymnastics, volleyball, basketball, and aerobic show a much higher osteogenic effect than sports which do not require such loading, e.g. cycling, rowing and swimming. Many of these scientific reports concern female players who have ended their sports career. The presented study provides evidence for positive effect of physical activity on bone tissue metabolism in the junior female professional volleyball players.  It was found that in the female athletes who professionally practice this sport discipline aged 19-21, the bone characteristics were higher in both humerus bones, and in the whole skeleton. The results obtained are in accordance with a study by Valente-dos-Santos et al. [9] conducted among volleyball players aged 14-17 from Portuguese clubs. The researchers observed that the whole-skeleton mineral density in the junior volleyball players was 1.184 g/cm² , and was significantly higher compared to females practising swimming, within the range of 5.5%.

Diet is one of the most important factors modifying the mineralization of the bone tissue. A great role in the osteoporosis prevention is ascribed to an appropriate content of calcium and vitamin D in the diet.  The conducted studies indicted that daily food rations of both volleyball players and young women from the control group did not supply the recommended amount of calcium and vitamin D, compliant with nutritional standards.  Calcium deficiency in combination with the vitamin D deficiency, with the disturbed process of intestinal absorption results in an increased resorption of bone tissue. Farrokhyar [10] assessed the vitamin D deficiency scale analyzing the 25(OH)D blood levels; its deficiency was observed in as many as 56% of sports persons, and it was conditioned by the geographic location.  It is also important for the proper bone mineralization to maintain calcium-phosphate homeostasis; therefore, the ratio between these elements in food should be 1:1. In our study this homeostasis was disturbed. Magnesium plays an important role in many basic processes within the cell, muscle contractility, in mineral homeostasis of the body and skeleton. It may affect the formation of hydroxyapatite crystals and result in an increase in the mineral bone density. The abnormalities observed in the diet of young females need to be corrected. 

Conclusions. It is recommended to constantly monitor bone parameters of the junior female athletes in the period of reaching their peak bone mass is advisable in terms of prevention of osteoporosis as female athletes are at increased risk of this disease. Such a monitoring should be multifaceted, taking into account the nutrition model and hormonal diagnosis.

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