Anna-Liisa Parm will defend her thesis "Bone mineralization in rhythmic gymnasts before puberty: associations with selected anthropometrical, body compositional and hormonal parameters" on 29 August 2012 at 12 o'clock in the Senate's Hall of the University of Tartu, applying for the degree of Doctor of Philosophy in exercise and sport sciences.
Supervisors: Professor Toivo Jürimäe and Professor Jaak Jürimäe.
Opponent: Professor Sigitas Kamandulis (Lithuanian Academy of Physical Education).
Osteoporosis is a major global public health concern. Individuals who achieve a higher peak bone mass during childhood might prevent osteoporosis in later life. Factors predicting bone mineral density in children are genetic factors, nutrition habits, body composition, physical activity level, endocrine status, and timing of pubertal maturation. Body composition affects bone by mechanical loading and hormones (leptin, adiponectin, ghrelin). These hormones predict bone mineral density by body composition and central nervous system. Fat free mass correlates positively with bone mineral density, but it has been found that fat mass can be a positive or negative independent determinant of bone mass. Regular high-impact weight-bearing physical activity is certainly one of the main factors for bone development. Rhythmic gymnastics seems to be especially osteogenic in children, probably due to high-volume, high-impact training and the involvement at a relatively early age (3-4 years). The relationships between athletes' bone mineral density and factors mentioned before have been extensively studied, however, there is few information how intensive physical activity is related to bone mineral density in prepubertal gymnasts whose body mass is lower than in inactive controls. The aim of the thesis was to investigate possible associations of specific anthropometrical, body compositional and hormonal values with bone mineral parameters in prepubertal rhythmic gymnasts and untrained controls. Gymnasts had significantly higher bone mineral density and lower body mass and leptin concentration than controls. In rhythmic gymnasts bone mineral density was related with fat mass and in untrained controls with fat free mass, leptin and ghrelin concentration. So it can be assumed that high-impact activity has an explicit effect on bone mineralization, although gymnasts have lower body mass and leptin conentration compared to untrained controls.