Sprint and upper limbs power field tests for the screening of low bone mineral density in children

Abstract

Background: The possibility of carrying out screening, with acceptable accuracy, of a child’s bone mass status based on a physical fitness test can advance the concept of health-related physical fitness. In addition, the relevance of the applicability of this type of screening in educational environments is mainly due to the difficulty of direct assessments of bone health indicators. This study aimed to propose cut-off points for physical fitness tests based on children’s bone health indicators.Methods: This is a two-phase cross-sectional study. Phase-1: 160 children (6–11 years-old) performed the 20-m sprint test (20-mST) and the 2 kg medicine ball throw test (2 kgMBTT). Areal bone mineral density (aBMD) and content was assessed by DXA. The area under the ROC curve greater than 70% was considered valid. Phase-2: It was carried out a secondary analysis in a sample with 8,750 Brazilians (6–11 years-old). The percentile values (identified in phase-1) were used to identify the values of the cut-off points in the unit of measurement of the tests. The validation of the cut-off points found was by odds ratio values and p ≤ 0.05.Results: Phase 1: The areas under the ROC curve were 0.710, 0.712 (boys and girls–20-mST), 0.703, and 0.806 (boys and girls–2 kgMBTT) with total spine and pelvis aBMD as the outcome. Phase 2: From percentile values, we find valid cut-off points in the Brazilian sample (OR > 3.00; p < 0.001) for boys and girls. Values ranged between 5.22 s–4.00 s to 20-mST and between 125.0 cm–160.0 cm to 2 kgMBTT. Conclusion. The 20-mST and the 2 kgMBTT presented sufficient accuracy for the screening of children aged between 6 and 11 years with greater chances of having low aBMD in the total spine and pelvis, with valid cut-off points.

Secular trends in the physical fitness of Brazilian youth: Evidence that fitness is declining for the majority but not for a fit minority

“…It is also difficult to compare the results relating to medicine ball throw performance to prior studies, as no prior work examining secular trends in physical fitness appears to have examined measures of upper body power [16][17][18]20 despite the medicine ball throw test being clinically relevant as a marker of children's bone health. 24 These temporal trends might have been anticipated, given the significant rise in BMI over the current time span. The five physical fitness test that declined over time/ years are weight/mass dependent (all five tests require the child to perform the test while carrying, limited by, their own body weight).…”

“…The reasons for this anomaly, in contrast to the other physical fitness tests employed in this study is unknown. It is also difficult to compare the results relating to medicine ball throw performance to prior studies, as no prior work examining secular trends in physical fitness appears to have examined measures of upper body power 16–18,20 despite the medicine ball throw test being clinically relevant as a marker of children's bone health 24 …”

“…For speed assessment, we used the 20-meters sprint test, as prior research identified this test as valid for screening low bone density in Brazilian children (ROC curves were 0.710 for boys, and 0.712 for girls). 24 The researcher demarcates a 20-meter runway with three parallel lines on the ground as follows: the first (start line), the second, 20 m away from the first (timeline) and the third line, marked by two meters from the second (finish line) to serve as a finishing reference for the student in an attempt to avoid deceleration before crossing the timeline. The appraiser must start the stopwatch when the participant takes the first step and touches the ground for the first time and the stopwatch will be stopped when the participant, crosses the second line (timeline).…”

“…For upper muscle power assessment, we used the 2 kg medicine ball throw test, this test proved to be valid for screening low bone density in Brazilian children (ROC curves were 0.703 for boys, and 0.806 for girls). 24 The child sits with knees extended, legs together and back fully supported by the wall. The child holds the medicine ball to their chest with elbows bent.…”