Lapsuuden ja nuoruuden lihaskunto ja luuterveys : lihaskunto lasten ja nuorten luuterveyden seulonnassa

he purpose of this thesis was to investigate association between muscular fitness and bone health. In addition, it was investigated if it is possible to define cut-points for muscular fitness tests to identify girls and boys at increased bone health risk. The data used in this study was a part from the study by University of Eastern Finland, Physical Activity and Nutrition in Children. The analysis in this thesis was made by using assessments from the baseline, 2-year follow-up and 8-year follow-up assessments. At the time of baseline assessments children were on the first class of Finnish primary school. The analysises included assessments from 451 children (220 girls, 231 boys) at baseline, 357 children (177 girls, 180 boys) from 2-year follow-up, and 238 adolescents (112 girls, 126 boys) from 8-year follow-up. Muscular fitness measurements were handgrip strength per lean mass, standing long jump and 30 seconds sit-up test. Bone health measurements were total body less head bone mineral content (TBLH BMC) and total body less head areal bone mineral density (TBLH aBMD). TBLH BMC and TBLH aBMD were measured using dual-energy X-ray absorptiometry (DXA) -device. The association between muscular fitness and bone health were investigated by using linear regression analysis. Children and adolescence with decreased bone health were determined to have TBLH BMC or TBLH aBMD ≤ -1 standard deviation from the assessment sample. Receiver operating characteristic (ROC) -curve was used to investigate if it was possible to define cut-points for muscle fitness tests to enable separating children and adolescents with increased bone health risk. In this thesis, the associations between muscular fitness and bone health varied by age and muscular fitness test. Standing long jump result under 214,5 cm indicated fair ability to separate the boys with lowered TBLH aBMD from the other boys at 8-year follow-up at the age of 15- 17 years The other muscular fitness tests analysed by ROC-curve indicated poor ability to differentiate children / adolescents with increased bone health risk. TBLH BMC and TBLH aBMD were not assessed relative to children’s height, which may have affected on reliability of the results and the determined cut-points.