BACKGROUND: The aim of this cross-sectional study was to examine the ability of a children's physical activity questionnaire (cPAQ) to assess physical activity levels and bone health status of school children.
METHODS: Subjects consisted of 90 pre-pubertal and early pubertal children aged 9-10 years. Components of physical activity were assessed using metabolic intensity (METPA) scores and mechanical bone strain (MECHPA) scores. An Actical accelerometer was used to validate METPA scores among a sub-sample of 57 children. Reliability was assessed by test-retesting all children after a 7 day interval. Whole body bone mineral content (BMC) was measured using dual-energy X-ray absorptiometry.
RESULTS: The reliability of cPAQ for assessment of various categories of physical activity was moderate to high (r ranged from 0.55 to 0.68, P < 0.001). Agreement was fair for repeated use of the cPAQ (Cohen's kappa = 0.32, P < 0.001). Bland-Altman plots show cPAQ had fair agreement only for moderate activity (mean difference 35.4 min/week; 95% limits of agreement -434.0 to +504.9 min/week). Approximately 69.6% of children were correctly classified (into the same or adjacent quartiles) according to the quartiles of BMC for METPA score, and 58.7% were correctly classified according to MECHPA score. Only 10.9% and 12.0% of children were grossly misclassified as compared to METPA and MECHPA scores, respectively.
CONCLUSIONS: The cPAQ has reasonable validity in assessing moderate physical activity, and it demonstrates good ability to accurately classify children according to BMC. It fails, however, to assess other activity levels, suggesting that objective measurement is still a better method of assessment of physical activity among primary school children.
The effects of deconditioning on exercise-induced bone gains in rats were investigated in 12-week-old female WKY rats performing a standard jumping exercise regimen for either 8, 12 or 24 weeks, followed by sedentary periods of either 24, 12 or 0 weeks, respectively. Age-matched controls received no exercise over the same period. At the end of the training/sedentary period, the tibiae were harvested for analyses of bone parameters. Gains in tibial fat-free dry weight decayed within 12 weeks of deconditioning, but gains in tibial ultimate bending force (strength), maximum diameter and cortical area were still present at 12 weeks of deconditioning. With the exception of cortical area, all other exercise-induced bone gains decayed by the 24th week of deconditioning. It appears that the decay in exercise-induced bone gains in strength, physical and morphological properties is not uniform, and that gains in fat-free dry weight seem to decay earlier.
Between 1976 and 1979, hand radiographs of 112 Malay children, 55 males and 57 females aged from 12 to 28 months, from higher socio-economic class families were obtained and studied by two radiologists. These children were part of a longitudinal study on growth and development. A total of 268 hand and wrist radiographs were taken, which the radiologists read independently of each other using the Greulich and Pyle Atlas. The bone age was then compared with the chronological age and the difference, if any, was noted and 'scored'. It was found that 83.4% of cases for males and 94.8% of cases for females matched within the +/- 6 months discrepancy range. For practical purposes therefore, our population may use the Greulich-Pyle Atlas with a good degree of confidence. Typical hand radiographs of male and female Malay children at 12, 18 and 24 months of age are also presented and these may be used as standards for Malaysian children at the respective age groups.
In this study the surface properties of two particulate coral and polyhydroxybutrate (PHB) were studied in order to characterize them prior to use in composite production. Coral powder and PHB particle were evaluated using scanning electron microscopy and confocal laser scanning microscopy, to measure surface porosity and pores size. The results showed that coral powder has multiple pleomorphic micropores cross each others give appearance of micro-interconnectivity. Some pore reached to 18 microm with an average porosity of 70%. PHB revealed multiple different size pores extended to the depth, with an average some times reach 25 microm and porosity 45%. These findings demonstrate that both coral and PHB have excellent pores size and porosity that facilitate bone in growth, vascular invasion and bone development. We believe that incorporation of coral powder into PHB will make an excellent composite scaffold for tissue engineering.
Chronic psychological stress affects many body systems, including the skeleton, through various mechanisms. This review aims to provide an overview of the factors mediating the relationship between psychological stress and bone health. These factors can be divided into physiological and behavioural changes induced by psychological stress. The physiological factors involve endocrinological changes, such as increased glucocorticoids, prolactin, leptin and parathyroid hormone levels and reduced gonadal hormones. Low-grade inflammation and hyperactivation of the sympathetic nervous system during psychological stress are also physiological changes detrimental to bone health. The behavioural changes during mental stress, such as altered dietary pattern, cigarette smoking, alcoholism and physical inactivity, also threaten the skeletal system. Psychological stress may be partly responsible for epigenetic regulation of skeletal development. It may also mediate the relationship between socioeconomic status and bone health. However, more direct evidence is required to prove these hypotheses. In conclusion, chronic psychological stress should be recognised as a risk factor of osteoporosis and stress-coping methods should be incorporated as part of the comprehensive osteoporosis-preventing strategy.