The Relationship between Physical Activity and Bone during Adolescence Differs according to Sex and Biological Maturity

This study examines the relationships between bone mass, physical activity, and maturational status in healthy adolescent boys and girls. Methods. Ninety-nine early high-school (Year 9) students were recruited. Physical activity and other lifestyle habits were recorded via questionnaire. Anthropometrics, muscle power, calcaneal broadband ultrasound attenuation (BUA), bone mineral content (BMC), and lean tissue mass were measured. Maturity was determined by Tanner stage and estimated age of peak height velocity (APHV). Results. Boys had greater APHV, weight, height, muscle power, and dietary calcium than girls (P < .05). Boys exhibited greater femoral neck BMC and trochanteric BMC while girls had higher BUA and spine BMAD (P < .05). Physical activity and vertical jump predicted BMAD and BUA most strongly for boys whereas years from APHV were the strongest predictor for girls. Conclusion. Sex-specific relationships exist between physical activity, maturity and bone mass during adolescence

Seasonal change in bone, muscle and fat in professional rugby league players and its relationship to injury: A cohort study

OBJECTIVES: To examine the anthropometric characteristics of an Australian National Rugby League team and identify the relationship to type and incidence of injuries sustained during a professional season. It was hypothesised that body composition would not change discernibly across a season and that injury would be negatively related to preseason bone and muscle mass. DESIGN: A repeated measure, prospective, observational, cohort study. SETTING: Griffith University, Gold Coast, Australia. PARTICIPANTS: 37 professional male Australian National Rugby League players, 24.3 (3.8) years of age were recruited for preseason 1 testing, of whom 25 were retested preseason 2. PRIMARY AND SECONDARY OUTCOME MEASURES: Primary outcome measures included biometrics; body composition (bone, muscle and fat mass; dual-energy x-ray absorptiometry; XR800, Norland Medical Systems, Inc); bone geometry and strength (peripheral quantitative CT; XCT 3000, Stratec); calcaneal broadband ultrasound attenuation (BUA; QUS-2, Quidel); diet and physical activity history. Secondary outcome measures included player injuries across a single playing season. RESULTS: Lean mass decreased progressively throughout the season (pre=81.45(7.76) kg; post=79.89(6.72) kg; p≤0.05), while whole body (WB) bone mineral density (BMD) increased until mid-season (pre=1.235(0.087) g/cm(2); mid=1.296(0.093) g/cm(2); p≤0.001) then decreased thereafter (post=1.256(0.100); p≤0.001). Start-of-season WB BMD, fat and lean mass, weight and tibial mass measured at the 38% site predicted bone injury incidence, but no other relationship was observed between body composition and injury. CONCLUSIONS: Significant anthropometric changes were observed in players across a professional rugby league season, including an overall loss of muscle and an initial increase, followed by a decrease in bone mass. Strong relationships between anthropometry and incidence of injury were not observed. Long-term tracking of large rugby league cohorts is indicated to obtain more injury data in order to examine anthropometric relationships with greater statistical power

Are Bone and Muscle Changes from POWER PE, an 8-month In-school Jumping Intervention, Maintained at Three Years?

Our aim was to determine if the musculoskeletal benefits of a twice-weekly, school-based, jumping regime in healthy adolescent boys and girls were maintained three years later. Subjects of the original POWER PE trial (n = 99) were contacted and asked to undergo retesting three years after cessation of the intervention. All original measures were completed including: sitting height, standing height, weight, calcaneal broadband ultrasound attenuation (BUA), whole body, hip and spine bone mineral content (BMC), lean tissue mass, and fat mass. Physical activity was recorded with the bone-specific physical activity questionnaire (BPAQ) and calcium intake was estimated with a calcium-focussed food questionnaire. Maturity was determined by Tanner staging and estimation of the age of peak height velocity (PHV). Twenty-nine adolescents aged 17.3±0.4 years agreed to participate. Three years after the intervention, there were no differences in subject characteristics between control and intervention groups (p>0.05). Three-year change in weight, lean mass, and fat mass were similar between groups (p>0.05). There were no significant group differences in three-year change in BUA or BMC at any site (p>0.05), although the between-group difference in femoral neck BMC at follow-up exceeded the least significant change. While significant group differences were not observed three years after cessation of the intervention, changes in bone parameters occurred in parallel for intervention and control groups such that the original benefits of the intervention observed within the treatment group were sustained

Sequence-based prediction for vaccine strain selection and identification of antigenic variability in foot-and-mouth disease virus

Identifying when past exposure to an infectious disease will protect against newly emerging strains is central to understanding the spread and the severity of epidemics, but the prediction of viral cross-protection remains an important unsolved problem. For foot-and-mouth disease virus (FMDV) research in particular, improved methods for predicting this cross-protection are critical for predicting the severity of outbreaks within endemic settings where multiple serotypes and subtypes commonly co-circulate, as well as for deciding whether appropriate vaccine(s) exist and how much they could mitigate the effects of any outbreak. To identify antigenic relationships and their predictors, we used linear mixed effects models to account for variation in pairwise cross-neutralization titres using only viral sequences and structural data. We identified those substitutions in surface-exposed structural proteins that are correlates of loss of cross-reactivity. These allowed prediction of both the best vaccine match for any single virus and the breadth of coverage of new vaccine candidates from their capsid sequences as effectively as or better than serology. Sub-sequences chosen by the model-building process all contained sites that are known epitopes on other serotypes. Furthermore, for the SAT1 serotype, for which epitopes have never previously been identified, we provide strong evidence - by controlling for phylogenetic structure - for the presence of three epitopes across a panel of viruses and quantify the relative significance of some individual residues in determining cross-neutralization. Identifying and quantifying the importance of sites that predict viral strain cross-reactivity not just for single viruses but across entire serotypes can help in the design of vaccines with better targeting and broader coverage. These techniques can be generalized to any infectious agents where cross-reactivity assays have been carried out. As the parameterization uses pre-existing datasets, this approach quickly and cheaply increases both our understanding of antigenic relationships and our power to control disease

Characterisation of the Mechanical Loads and Metabolic Intensity of the CAPO Kids Exercise Intervention for Healthy Primary School Children

Sedentarism is associated with obesity and other chronic diseases at all ages. Increasing physical activity with in-school interventions, focusing on energy expenditure and bone loading reduces risk of a number of costly chronic diseases. The aim of the current study was to characterise the metabolic and musculoskeletal load intensity of the recent successful CAPO Kids exercise intervention. Pre and early pubertal children (10.4 ± 0.5 years old) from the CAPO Kids trial wore an armband sensor to estimate energy expenditure during a 10-minute CAPO Kids session. Eleven participants performed manoeuvres from the session on a force platform to determine vertical ground reaction forces. In total, 28 boys and 20 girls had armband measures and 11 boys and girls undertook GRF testing. The energy expenditure associated with the 10-minute session was 39.7 ± 9.3 kcal, with an average of 4 kcal·min-1. The intensity of physical activity was ‘vigorous’ to ‘very vigorous’ for 34% of the session. Vertical ground reaction forces of the CAPO Kids manoeuvres ranged from 1.3 ± 0.2 BW (cartwheels) to 5.4 ± 2.3 BW (360° jump). CAPO Kids generates adequate load intensity to stimulate positive health adaptations in both metabolic and musculoskeletal systems of pre and early pubertal children

Baseline, 8-month, and 44-month femoral neck BMC (A), lumbar spine BMC (B), whole body BMC (C), and calcaneal BUA (D) for intervention (open circles) and control subjects (closed circles).

<p>Key: BMC, bone mineral content; BUA, broadband ultrasound attenuation. * represents significant difference with baseline measure. ∧ represents significant difference with 8-month measure.</p

Subject characteristics (mean ± SD) for controls and intervention subjects three years post-intervention (n = 29).

<p>Key: APHV, Age of peak height velocity; BMI, body mass index; BPAQ, bone-specific physical activity questionnaire.</p

Bone and body composition values at baseline, 8 months, and 44 months (mean ± SD) for controls and intervention subjects based on intention-to-treat analysis (n = 99).

<p>Key: BUA, broadband ultrasound attenuation; FN BMC, femoral neck bone mineral content; LS BMC, lumbar spine bone mineral content; WB BMC, whole body bone mineral content.</p>*<p>represents significant difference with baseline measure.</p