As indoor athletes, competitive gymnasts and swimmers can face the problem of a potential vitamin D deficiency. In the last decades, indoor sports participants have been faced with the problem of an institutionalized lifestyle and, in some places, a lower exposure to sun, which is also associated with the geographical area with a lower or higher UV index, especially in autumn, winter, and early spring (from October to April), when the day is shorter and the clock shifts to winter time. The problem with gymnasts and swimmers lies in daily trainings in the gym and pool and in the daily rest between two trainings, which can be spend more or less institutionally. The investigators wanted to examine the vitamin D status related to bone mineral density, body composition and various cardiovascular markers among young competitive gymnasts and swimmers after winter time. The investigators want to potentially give more solid but sensible recommendations for trainers, athletes, parents and sports doctors when it comes to vitamin D supplementations for indoor female athletes.

In this cross-sectional survey, the investigators will document vitamin D and the status of other micronutrients related to bone mineral density, body composition and a variety of risk factors for chronic non-communicable diseases.

The investigators hypothesize that there exists a serious problem of vitamin D deficiency among indoor athletes related to bone health, injuries and general health - especially when they are not using supplements. It is well known that vitamin D may improve athletic performance in vitamin D-deficient athletes.

International and national-level female gymnasts and swimmers that will be enrolled will sign an informed consent statement for the inclusion in this survey and the choice to participate in the study will be made by coaches and participants themselves and, in the event of females under 18 years of age, also by their parents, in accordance with the Helsinki declaration.

The investigators plan to enroll at least 30 female participants (15 gymnasts and 15 swimmers) who compete on an international and national level and are older than 12 years of age.

The investigators will measure the athletes' biochemistry in overnight fasted state (micronutrients, including vitamin D (25(OH)D), B12, Ca, Fe, Mg, K and P, lipids, liver enzymes, glucose, creatinine, etc.), their seated blood pressure status, bone mineral density (also segmental) and body composition, using Dual-energy X-ray absorptiometry (DXA), their dietary choice and nutrition intake status, using standardized Food frequency questionnaire (FFQ), their training characteristics, injury status and menstrual status. Athletes who are using vitamin D supplements or who have attended a one-month training camp in the southern geographical zone (Africa) will serve us as control group.

Inclusion Criteria:

• international and national level
• Signed informed consent for participation in the study

Exclusion Criteria:

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Sport