The Secret Sauce? Taking the Mystery Out of Scaling-Up School-Based Physical Activity Interventions.

Over the last 4 decades, physical activity researchers have invested heavily in determining "what works" to promote healthy behaviors in schools. Single and multicomponent school-based interventions that target physical education, active transportation, and/or classroom activity breaks effectively increased physical activity among children and youth. Yet, few of these interventions are ever scaled-up and implemented under real-world conditions and in diverse populations. To achieve population-level health benefits, there is a need to design school-based health-promoting interventions for scalability and to consider key aspects of the scale-up process. In this opinion piece, we aim to identify challenges and advance knowledge and action toward scaling-up school-based physical activity interventions. We highlight the key roles of planning for scale-up at the outset, scale-up pathways, trust among partners and program support, program adaptation, evaluation of scale-up, and barriers and facilitators to scaling-up. We draw upon our experience scaling-up effective school-based interventions and provide a solid foundation from which others can work toward bridging the implementation-to-scale-up gap.

Long-Term Change in Bone Mineral Density in Women Living With HIV: A 10-Year Prospective Controlled Cohort Study.

Women living with HIV (WLWH) may be at higher risk for osteoporosis and fragility fractures. However, limited prospective data describe long-term trajectories of bone mineral density (BMD) in WLWH versus women without HIV. Thus, in this prospective study, we aimed to compare 10-year change in areal BMD (aBMD) between WLWH (n = 49; 36.8 ± 8.8 years; 96% pre/perimenopausal) and HIV-negative women (population-based controls; n = 49; 41.9 ± 9.2 years; 80% pre/perimenopausal). In an exploratory analysis, we compared fracture history between WLWH and controls. Outcomes were lumbar spine (L1 to L4), total hip, and femoral neck aBMD at baseline and follow-up, which occurred at 13 and 10 years in WLWH and controls, respectively. We fit multivariable regression models to compare baseline and 10-year change in aBMD between groups, adjusting for osteoporosis risk factors. Within WLWH, we examined associations between aBMD and HIV-related factors, including combination antiretroviral therapy (cART) duration. WLWH were diagnosed 6.5 ± 3.7 years before baseline, 80% were on cART for 241 ± 142 weeks, and 49% had HIV plasma viral load <40 copies/mL. Before and after adjusting for osteoporosis risk factors, baseline and 10-year change in aBMD did not differ between WLWH and controls at any site. At baseline, more WLWH than controls reported a history of low-trauma fracture (30% versus 10%, p < 0.05) and major osteoporotic fracture (17% versus 4%, p < 0.05). During follow-up, the number of WLWH and controls with incident fragility fracture was not significantly different. Lifetime cART duration and tenofovir use were not associated with aBMD 10-year percent change. Higher CD4 count at baseline was positively associated with femoral neck aBMD 10-year percent change. Long-term aBMD change in this small WLWH cohort paralleled normal aging, with no evidence of influence from cART use; however, these results should be interpreted with caution given the small sample size. Larger cohort studies are needed to confirm these findings. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

What is the 'voltage drop' when an effective health promoting intervention for older adults-Choose to Move (Phase 3)-Is implemented at broad scale?

BACKGROUND: Choose to Move (CTM), an effective health-promoting intervention for older adults, was scaled-up across British Columbia, Canada. Adaptations that enable implementation at scale may lead to 'voltage drop'-diminished positive effects of the intervention. For CTM Phase 3 we assessed: i. implementation; ii. impact on physical activity, mobility, social isolation, loneliness and health-related quality of life (impact outcomes); iii. whether intervention effects were maintained; iv) voltage drop, compared with previous CTM phases. METHODS: We conducted a type 2 hybrid effectiveness-implementation pre-post study of CTM; older adult participants (n = 1012; mean age 72.9, SD = 6.3 years; 80.6% female) were recruited by community delivery partners. We assessed CTM implementation indicators and impact outcomes via survey at 0 (baseline), 3 (mid-intervention), 6 (end-intervention) and 18 (12-month follow-up) months. We fitted mixed-effects models to describe change in impact outcomes in younger (60-74 years) and older (≥ 75 years) participants. We quantified voltage drop as percent of effect size (change from baseline to 3- and 6-months) retained in Phase 3 compared with Phases 1-2. RESULTS: Adaptation did not compromise fidelity of CTM Phase 3 as program components were delivered as intended. PA increased during the first 3 months in younger (+1 days/week) and older (+0.9 days/week) participants (p<0.001), and was maintained at 6- and 18-months. In all participants, social isolation and loneliness decreased during the intervention, but increased during follow-up. Mobility improved during the intervention in younger participants only. Health-related quality of life according to EQ-5D-5L score did not change significantly in younger or older participants. However, EQ-5D-5L visual analog scale score increased during the intervention in younger participants (p<0.001), and this increase was maintained during follow-up. Across all outcomes, the median difference in effect size, or voltage drop, between Phase 3 and Phases 1-2 was 52.6%. However, declines in social isolation were almost two times greater in Phase 3, compared with Phases 1-2. CONCLUSION: Benefits of health-promoting interventions-like CTM-can be retained when implemented at broad scale. Diminished social isolation in Phase 3 reflects how CTM was adapted to enhance opportunities for older adults to socially connect. Thus, although intervention effects may be reduced at scale-up, voltage drop is not inevitable.

A 4-Yr Mixed Longitudinal Study of Health Behaviors and Fat Mass Accrual during Adolescence and Early Adulthood.

PURPOSE: Physical activity (PA), sedentary time (SED), and energy intake (EI) are associated with fat mass accrual in children and youth. Previous studies relied primarily on cross-sectional designs and proxy measures of body composition such as body mass index. We aimed to prospectively investigate associations between PA, SED, EI, and total body fat mass accrual using dual-energy x-ray absorptiometry. METHODS: This analysis of the mixed longitudinal Healthy Bones III Study included data from 312 participants (138 boys age 9 to 21 yr at baseline). For each participant, we acquired a maximum of four annual total body dual-energy x-ray absorptiometry scans from which we determined fat mass (in kilograms; n = 748 observations). We assessed total PA, moderate-to-vigorous PA (MVPA) and SED with accelerometers (ActiGraph GT1M) and measured EI via 24-h dietary recall. We fit sex-specific multilevel models adjusting for maturity (years from age at peak height velocity (APHV)), weight status, ethnicity, total PA, MVPA, SED, and EI. RESULTS: Boys and girls demonstrated divergent trajectories of fat mass accrual; rate of fat mass accrual in girls was four times greater than boys at APHV and increased across adolescence, whereas boys' fat mass plateaued after APHV. In boys, within-person change in MVPA negatively predicted fat mass independent of SED; each annual increase in MVPA of 6 min·d -1 was associated with a 0.21-kg lower fat mass. In girls, between-person average MVPA negatively predicted fat mass accrual independent of SED; greater MVPA of 4 min·d -1 across adolescence was associated with a 0.31-kg lower fat mass. CONCLUSIONS: MVPA demonstrates an independent and negative effect on fat mass in boys and girls. Given different trajectories of fat mass accrual and movement behaviors between boys and girls, PA interventions aimed at preventing obesity in youth may benefit from a sex and gendered approach.

Pragmatic Evaluation of Older Adults' Physical Activity in Scale-Up Studies: Is the Single-Item Measure a Reasonable Option?

Convergent validity and responsiveness to change of the single-item physical activity measure were assessed in adults aged 60 years and older, at baseline (n = 205) and 6 months (n = 177) of a health promotion program, Choose to Move. Spearman correlations were used to examine associations between physical activity as measured by the single-item measure and the Community Health Activities Model Program for Seniors (CHAMPS) questionnaire at baseline and for 6-month change in all participants and for sex and age (60-74 years, and ≥75 years) subgroups. Effect size assessed responsiveness to change in physical activity for both tools. Baseline physical activity by the single-item measure correlated moderately with physical activity by the CHAMPS questionnaire in all participants and subgroups. Correlations were weaker for change in physical activity. Effect size for physical activity change was larger for the single-item measure than for the CHAMPS questionnaire. The single-item measure is a valid, pragmatic tool for use in intervention and scale-up studies with older adults.

Status Quo or Drop-Off: Do Older Adults Maintain Benefits From Choose to Move-A Scaled-Up Physical Activity Program-12 Months After Withdrawing the Intervention?

BACKGROUND: Choose to Move is one of few scaled-up health-promoting interventions for older adults. The authors evaluated whether Choose to Move participants maintained their intervention-related gains in physical activity (PA), mobility, and social connectedness 12 months after the intervention ended. METHODS: The authors assessed PA, mobility, loneliness, social isolation, and muscle strength via questionnaire and objective measures in 235 older adults at 0 months (baseline), 6 months (end of intervention), and 18 months (12-months postintervention). The authors fitted linear mixed models to examine the change in each outcome from 6 to 18 months (primary objective) and 0 to 18 months (secondary objective) and reported by age group (60-74 and ≥75 y). RESULTS: In younger participants, PA decreased between 6 and 18 months, but remained significantly higher than at baseline. Intervention-related benefits in loneliness, social isolation, mobility, and muscle strength were maintained between 6 and 18 months in the younger participants. Older participants maintained their intervention benefits in loneliness, mobility, and muscle strength. When compared with baseline values, PA levels in older participants were unchanged, whereas social isolation increased. CONCLUSIONS: Older adults maintained some, but not all, health benefits of Choose to Move 12 months after the intervention ended. Long-term commitments are needed to deliver effective health-promoting interventions for older adults if benefits are to be maintained.

Scaling up Action Schools! BC: How Does Voltage Drop at Scale Affect Student Level Outcomes? A Cluster Randomized Controlled Trial.

Action Schools! BC (AS! BC) was scaled-up from an efficacy trial to province-wide delivery across 11 years (2004-2015). In this study we: (1) describe strategies that supported implementation and scale-up; (2) evaluate implementation (teachers' physical activity (PA) delivery) and student's PA and cardiorespiratory fitness (CRF) within a cluster randomized controlled trial during years 2 and 3 of scale-up; and (3) assess relationships between teacher-level implementation and student-level outcomes. We classified implementation strategies as process, capacity-building or scale-up strategies. Elementary schools (n = 30) were randomized to intervention (INT; 16 schools; 747 students) or usual practice (UP; 14 schools; 782 students). We measured teachers' PA delivery (n = 179) using weekly logs; students' PA by questionnaire (n = 30 schools) and accelerometry (n = 9 schools); and students' CRF by 20-m shuttle run (n = 25 schools). INT teachers delivered more PA than UP teachers in year 1 (+33.8 min/week, 95% CI 12.7, 54.9) but not year 2 (+18.8 min/week, 95% CI -0.8, 38.3). Unadjusted change in CRF was 36% and 27% higher in INT girls and boys, respectively, compared with their UP peers (year 1; effect size 0.28-0.48). Total PA delivered was associated with change in children's self-reported MVPA (year 1; r = 0.17, p = 0.02). Despite the 'voltage drop', scaling-up school-based PA models is feasible and may enhance children's health. Stakeholders must conceive of new ways to effectively sustain scaled-up health promoting interventions if we are to improve the health of students at a population level. Clinical Trials registration: NCT01412203.

Playing-Related Musculoskeletal Disorders, Risk Factors, and Treatment Efficacy in a Large Sample of Oboists.

OBJECTIVES: During their lifetimes, a majority of musicians experience playing-related musculoskeletal disorders (PRMD). PRMD prevalence is tied to instrument choice, yet most studies examine heterogeneous groups of musicians, leaving some high-risk groups such as oboists understudied. This paper aims to (1) ascertain the prevalence and nature of PRMDs in oboists, (2) determine relevant risk factors, and (3) evaluate the efficacy of treatment methods in preventing and remedying injuries in oboe players. METHODS: A 10-question online questionnaire on PRMDs and their treatments was completed by 223 oboists. PRMDs were compared across gender, weekly playing hours, career level, age, and years of playing experience. RESULTS: Of all respondents, 74.9% (167/223) reported having had at least one PRMD in their lifetime. A majority of these injuries (61.9% of all respondents) were of moderate to extreme severity (5 or higher on a scale of 1 to 10). Females (mean = 5.88) reported significantly more severe injuries than males. No significant effects of career level (i.e., professional vs. student vs. amateur), age, or years of playing experience were observed. We found significant non-linear relationships between weekly playing hours and PRMD prevalence and severity. Injuries were most commonly on the right side of the body, with the right thumb, wrist, hand, and forearm being most affected in frequency and severity. Of those injuries for which recovery information was provided, only 26.1% of injuries were "completely recovered." The perceived effectiveness of a few treatments (physical therapy, rest, stretching, occupational therapy, massage) tended to be ranked more highly than others. CONCLUSION: The oboists in this study experienced high rates of PRMD, particularly in the right upper extremities. Females and those playing 7-9 and 16-18 h per week reported a significantly higher severity of injuries than other groups.

Physical activity is good for older adults-but is programme implementation being overlooked? A systematic review of intervention studies that reported frameworks or measures of implementation.

OBJECTIVE: To examine older adult physical activity (PA) intervention studies that evaluated implementation and/or scale-up. Research question 1: What implementation and/or scale-up indicators (specific, observable and measurable characteristics that show the progress of implementation) were reported? Research question 2: What implementation and/or scale-up frameworks were reported? Research question 3: Did studies evaluate the relationship between implementation or scale-up of the intervention and individual level health/behaviour outcomes? If yes, how? DESIGN: Systematic review. DATA SOURCES: Publications from electronic databases and hand searches (2000 to December 2019). ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Any PA intervention studies with community-dwelling older adult participants (mean age ≥60 years). Required indicators: (a) Must report amount of PA as an outcome, with validated self-report or objective measures, and (b) Must have reported at least one implementation or scale-up framework and/or one implementation or scale-up indicator. RESULTS: 137 studies were included for research question 1, 11 for question 2 and 22 for question 3. 137 studies reported an implementation indicator: 14 unique indicators. None were specified as indicators for scale-up evaluation. 11 studies were guided by an implementation or scale-up framework. 22 studies described a relationship between an implementation indicator and an individual-level health outcome. CONCLUSION: There is need for implementation research that extends beyond analysis at the individual level, includes clearly defined indicators and provides a guiding framework to support PA initiatives in older adults. Such implementation studies should evaluate factors in the broader context (eg,political, environmental) that influence scale-up. PROSPERO REGISTRATION: CRD42018091839.

Deficits in bone strength, density and microarchitecture in women living with HIV: A cross-sectional HR-pQCT study.

PURPOSE: With the advent of combined antiretroviral therapy (cART), life expectancy has increased among persons living with HIV, but so too has risk for comorbidities including osteoporosis and fragility fracture. To explore whether HIV status and cART influence three-dimensional measures of BMD, bone microarchitecture and strength we aimed to compare these outcomes between women living with HIV (WLWH; n = 50; 50.4 ± 1.2 years, 44% postmenopausal) and without HIV (controls; n = 50; 51.8 ± 1.2 years, 52% postmenopausal). METHODS: Outcomes were lumbar spine, total hip and femoral neck areal BMD by DXA; distal radius and tibia trabecular BMD, thickness and number, and cortical BMD and area by HR-pQCT; and finite element analysis-derived bone strength (failure load). Multivariable regression analysis compared bone outcomes between groups adjusting for known osteoporosis risk factors. Within WLWH, we examined associations between bone outcomes and HIV-related factors including disease severity and cART duration. RESULTS: WLWH were diagnosed 20 ± 4 years ago, were on cART for 123 ± 37 months and 80% had HIV plasma viral load <40 copies/mL. For women ≥50 years (n = 61), total hip aBMD T-Score was lower among WLWH than controls. Adjusted distal radius trabecular BMD and thickness and distal tibia trabecular BMD and failure load were 8-19% lower in WLWH than controls (p < 0.05). Cortical BMD and area did not differ between groups at either site. Lifetime cART duration and current plasma viral load were not associated with bone outcomes in WLWH; however, previous treatment with tenofovir was negatively associated with distal radius trabecular BMD and trabecular number and LS aBMD T-score. CONCLUSIONS: WLWH have compromised BMD, bone microarchitecture and strength vs. controls of similar age and reproductive status. Treatment with tenofovir may contribute to bone deficits in WLWH.

Body fat accrual trajectories for a sample of Asian-Canadian and Caucasian-Canadian children and youth: A longitudinal DXA-based study.

BACKGROUND: Body fat accrual trajectories can be used to monitor trends in body fat mass and identify potential health risks. Currently, no body fat percent (BF%) centile distance and velocity curves exist for Canadian youth. OBJECTIVES: To develop sex-specific and ethnic-specific BF% centile distance and velocity curves for White and Asian-Canadian youth. METHODS: We utilized 4734 observations from 944 participants (female = 487; Asian = 532) to create sex-specific BF% velocity curves for age 10 to 18 years and sex-specific and ethnic-specific BF% percentile distance curves for ages 9 to 18 years for White and Asian children. BF% was derived from whole body DXA scans. RESULTS: BF% centile distance curves for Asian and White girls were similar. BF% at most centiles plateaued around age 16 for Asian but not for White boys. Velocity curves for boys declined from age 11 to 13 years and then increased until age 18 years. For girls from 10 to 15 years, velocity curves converged towards the 50th centile then remained flat from 16 to 18 years. CONCLUSIONS: BF% distance and velocity centiles can be used to identify when an individual veers from an average BF% accrual trajectory. In future, these curves may be used to investigate differences in fat mass and accrual across Canada.

Feasibility and safety of a 6-month exercise program to increase bone and muscle strength in children with juvenile idiopathic arthritis.

BACKGROUND: Arthritis in childhood can be associated with muscle weakness around affected joints, low bone mass and low bone strength. Exercise is recognized as an important part of management of children with juvenile idiopathic arthritis (JIA) but the exercise prescription to best promote bone and muscle health is unknown. We therefore aimed to: 1. assess feasibility and safety of a 6-month home- and group-based exercise program for children with JIA; 2. estimate the effect of program participation on bone mass and strength, muscle function and clinical outcomes and 3. determine if any positive changes in bone and muscle outcomes are maintained 6 months later. METHODS: We recruited 24 children with JIA who were part of the Linking Exercise, Physical Activity and Pathophysiology in Childhood Arthritis (LEAP) study to participate in a 6-month home-based exercise program involving jumping and handgrip exercises, resistance training and one group exercise session per month. We assessed lumbar spine bone mass (dual energy X-ray absorptiometry), distal tibia and radius bone microarchitecture and strength (high-resolution peripheral quantitative computed tomography), muscle function (jumping mechanography, dynamometry) and clinical outcomes (joint assessment, function, health-related quality of life) at baseline, 6- and 12-months. Adherence was assessed using weekly activity logs. RESULTS: Thirteen children completed the 6-month intervention. Participants reported 9 adverse events and post-exercise pain was rare (0.4%). Fatigue improved, but there were no other sustained improvements in muscle, bone or clinical outcomes. Adherence to the exercise program was low (47%) and decreased over time. CONCLUSION: Children with JIA safely participated in a home-based exercise program designed to enhance muscle and bone strength. Fatigue improved, which may in turn facilitate physical activity participation. Prescribed exercise posed adherence challenges and efforts are needed to address facilitators and barriers to participation in and adherence to exercise programs among children with JIA. TRIAL REGISTRATION: Data of the children with JIA are from the LEAP study (Canadian Institutes of Health Research (CIHR; GRANT# 107535 ). http://www.leapjia.com/.

Physical activity, but not sedentary time, influences bone strength in late adolescence.

Physical activity is essential for optimal bone strength accrual, but we know little about interactions between physical activity, sedentary time, and bone outcomes in older adolescents. Physical activity (by accelerometer and self-report) positively predicted bone strength and the distal and midshaft tibia in 15-year-old boys and girls. Lean body mass mediated the relationship between physical activity and bone strength in adolescents. PURPOSE: To examine the influence of physical activity (PA) and sedentary time on bone strength, structure, and density in older adolescents. METHODS: We used peripheral quantitative computed tomography to estimate bone strength at the distal tibia (8% site; bone strength index, BSI) and tibial midshaft (50% site; polar strength strain index, SSIp) in adolescent boys (n = 86; 15.3 ± 0.4 years) and girls (n = 106; 15.3 ± 0.4 years). Using accelerometers (GT1M, Actigraph), we measured moderate-to-vigorous PA (MVPAAccel), vigorous PA (VPAAccel), and sedentary time in addition to self-reported MVPA (MVPAPAQ-A) and impact PA (ImpactPAPAQ-A). We examined relations between PA and sedentary time and bone outcomes, adjusting for ethnicity, maturity, tibial length, and total body lean mass. RESULTS: At the distal tibia, MVPAAccel and VPAAccel positively predicted BSI (explained 6-7% of the variance, p < 0.05). After adjusting for lean mass, only VPAAccel explained residual variance in BSI. At the tibial midshaft, MVPAAccel, but not VPAAccel, positively predicted SSIp (explained 3% of the variance, p = 0.01). Lean mass attenuated this association. MVPAPAQ-A and ImpactPAPAQ-A also positively predicted BSI and SSIp (explained 2-4% of the variance, p < 0.05), but only ImpactPAPAQ-A explained residual variance in BSI after accounting for lean mass. Sedentary time did not independently predict bone strength at either site. CONCLUSION: Greater tibial bone strength in active adolescents is mediated, in part, by lean mass. Despite spending most of their day in sedentary pursuits, adolescents' bone strength was not negatively influenced by sedentary time.

Sex-, Ethnic-, and Age-Specific Centile Curves for pQCT- and HR-pQCT-Derived Measures of Bone Structure and Strength in Adolescents and Young Adults.

There are presently no adolescent centile curves for bone parameters at the tibial midshaft using peripheral quantitative computed tomography (pQCT) or at the distal radius and tibia using high-resolution pQCT (HR-pQCT). Thus, we aimed to develop sex-, ethnic-, site-, and age-specific centile curves for pQCT and HR-pQCT-derived bone outcomes for youth and young adults aged 10 to 21 years. We acquired pQCT scans (XCT3000 or XCT2000) at the tibial midshaft (50% site) and HR-pQCT scans (XtremeCT) at the distal radius (7% site) and tibia (8% site) in a convenience sample of participants in the mixed-longitudinal University of British Columbia Healthy Bones III Study. We scanned 778 10- to 21-year-olds annually for a maximum of 11 years using pQCT (413 girls, 56% Asian; 365 boys, 54% Asian; n = 3160 observations) and 349 10- to 21-year-olds annually for a maximum of 4 years using HR-pQCT (189 girls, 51% Asian; 165 boys, 50% Asian; n = 1090 observations). For pQCT, we report cortical bone mineral density (BMD), total bone cross-sectional area, and polar strength-strain index. For HR-pQCT, we report standard measures (total BMD, trabecular number, thickness, and bone volume fraction) and automated segmentation measures (total bone cross-sectional area, cortical BMD, porosity, and thickness). We applied finite element analysis to estimate failure load. We applied the lamda, mu, sigma (LMS) method using LMS ChartMaker Light (version 2.5, The Institute of Child Health, London, UK) to construct LMS tables and centile plots. We report sex- and age-specific centiles (3rd, 10th, 25th, 50th, 75th, and 97th) for whites and Asians for pQCT bone parameters at the tibial midshaft and HR-pQCT bone parameters at the distal radius and tibia. These centile curves might be used by clinicians and scientists to interpret values or better understand trajectories of bone parameters in clinical populations, those from different geographic regions or of different ethnic origins. © 2018 American Society for Bone and Mineral Research.

Bone Strength in Girls and Boys After a Distal Radius Fracture: A 2-Year HR-pQCT Double Cohort Study.

We recently reported impaired bone strength in girls with low- to moderate-energy distal radius fractures (Fx) compared with girls with no history of forearm fractures (Non-Fx). We aimed to determine whether bone strength deficits observed at baseline were still present after 2 years. We assessed bone strength, microarchitecture, and bone mineral density (BMD) of the non-fractured (Fx) and non-dominant (Non-Fx) distal radius (7% site) at baseline, 12, and 24 months using high-resolution pQCT (Scanco Medical, Brüttisellen, Switzerland) in 104 girls (aged 11.0 ± 1.7 years; 47 Fx, 57 Non-Fx) and 157 boys (aged 12.7 ± 1.7 years; 86 Fx, 71 Non-Fx). Bone outcomes included total area (Tt.Ar) and bone mineral density (Tt.BMD), trabecular bone volume ratio (BV/TV), thickness (Tb.Th), separation (Tb.Sp), and number (Tb.N), and cortical BMD (Ct.BMD), thickness (Ct.Th), and porosity (Ct.Po). We used finite element analysis to estimate bone strength (failure load [F.Load]; ultimate stress [U.Stress]; load-to-strength ratio). We used sex-specific mixed-effects models to compare bone outcomes between Fx and Non-Fx over 2 years. In girls, those with fractures had 18% to 24% lower U.Stress and 5% to 9% lower Tt.BMD than Non-Fx at all time points (p < 0.017). In secondary analysis by fracture degree, girls with low-energy (LE) fractures had 19% to 21% lower F.Load, 25% to 47% lower U.Stress, 11% to 14% lower Tt.BMD, and 11% to 15% lower BV/TV than Non-Fx at all time points (p < 0.017). In contrast, boys' bone outcomes were similar between Fx and Non-Fx at all time points. In secondary analysis by fracture degree, boys with LE fractures had 10% lower Tt.BMD and 10% lower Ct.Th compared with Non-Fx at 12 months only. Deficits in distal radius bone strength and trabecular bone microarchitecture appear to track across 2 years after a forearm fracture in girls but not in boys. Longer follow-up is needed to determine whether deficits persist into adulthood in women and how they may influence future risk of fragility fracture. © 2017 American Society for Bone and Mineral Research.

Bouts of Vigorous Physical Activity and Bone Strength Accrual During Adolescence.

PURPOSE: We examined the influence of vigorous physical activity (VPA) bout frequency on bone strength accrual across adolescence, independent of total volume of VPA. METHODS: We measured VPA (6 metabolic equivalents; total volume and bout frequency <5 min in duration) annually using waist-worn accelerometers (ActiGraph GT1M) in 309 adolescents (9-20 y at baseline: 99, <13 y; 126, 13-18 y; 84, >18 y) over a maximum of 4 years. We applied finite element analysis to high-resolution peripheral quantitative computed tomography scans of the distal tibia (8% site) to estimate bone strength (failure load; F.Load, Newtons). We fit a mixed effects model with maturity offset (years from age at peak height velocity) as a random effect and sex, ethnicity, tibia length, lean body mass, and VPA (volume and bout frequency) as fixed effects. RESULTS: VPA volume and bout frequency were positively associated with F.Load across adolescence; however, VPA volume did not predict F.Load once VPA bout frequency was included in the model. Participants in the upper quartile of VPA bout frequency (∼33 bouts per day) had 10% (500 N) greater F.Load across adolescence compared with participants in the lowest quartile (∼9 bouts per day; P = .012). Each additional daily bout of VPA was associated with 21 N greater F.Load, independent of total volume of VPA. CONCLUSION: Frequent VPA should be promoted for optimal bone strength accrual.

Physical Activity, Sedentary Time, and Bone Strength From Childhood to Early Adulthood: A Mixed Longitudinal HR-pQCT study.

Bone strength is influenced by bone geometry, density, and bone microarchitecture, which adapt to increased mechanical loads during growth. Physical activity (PA) is essential for optimal bone strength accrual; however, less is known about how sedentary time influences bone strength and its determinants. Thus, our aim was to investigate the prospective associations between PA, sedentary time, and bone strength and its determinants during adolescence. We used HR-pQCT at distal tibia (8% site) and radius (7% site) in 173 girls and 136 boys (aged 9 to 20 years at baseline). We conducted a maximum of four annual measurements at the tibia (n = 785 observations) and radius (n = 582 observations). We assessed moderate-to-vigorous PA (MVPA) and sedentary time with accelerometers (ActiGraph GT1M). We aligned participants on maturity (years from age at peak height velocity) and fit a mixed-effects model adjusting for maturity, sex, ethnicity, leg muscle power, lean mass, limb length, dietary calcium, and MVPA in sedentary time models. MVPA was a positive independent predictor of bone strength (failure load [F.Load]) and bone volume fraction (BV/TV) at the tibia and radius, total area (Tt.Ar) and cortical porosity (Ct.Po) at the tibia, and negative predictor of load-to-strength ratio at the radius. Sedentary time was a negative independent predictor of Tt.Ar at both sites and Ct.Po at the tibia and a positive predictor of cortical thickness (Ct.Th), trabecular thickness (Tb.Th), and cortical bone mineral density (Ct.BMD) at the tibia. Bone parameters demonstrated maturity-specific associations with MVPA and sedentary time, whereby associations were strongest during early and mid-puberty. Our findings support the importance of PA for bone strength accrual and its determinants across adolescent growth and provide new evidence of a detrimental association of sedentary time with bone geometry but positive associations with microarchitecture. This study highlights maturity-specific relationships of bone strength and its determinants with loading and unloading. Future studies should evaluate the dose-response relationship and whether associations persist into adulthood. © 2017 American Society for Bone and Mineral Research.

Sex Differences and Growth-Related Adaptations in Bone Microarchitecture, Geometry, Density, and Strength From Childhood to Early Adulthood: A Mixed Longitudinal HR-pQCT Study.

Sex differences in bone strength and fracture risk are well documented. However, we know little about bone strength accrual during growth and adaptations in bone microstructure, density, and geometry that accompany gains in bone strength. Thus, our objectives were to (1) describe growth related adaptations in bone microarchitecture, geometry, density, and strength at the distal tibia and radius in boys and girls; and (2) compare differences in adaptations in bone microarchitecture, geometry, density, and strength between boys and girls. We used HR-pQCT at the distal tibia (8% site) and radius (7% site) in 184 boys and 209 girls (9 to 20 years old at baseline). We aligned boys and girls on a common maturational landmark (age at peak height velocity [APHV]) and fit a mixed effects model to these longitudinal data. Importantly, boys showed 28% to 63% greater estimated bone strength across 12 years of longitudinal growth. Boys showed 28% to 80% more porous cortices compared with girls at both sites across all biological ages, except at the radius at 9 years post-APHV. However, cortical density was similar between boys and girls at all ages at both sites, except at 9 years post-APHV at the tibia when girls' values were 2% greater than boys'. Boys showed 13% to 48% greater cortical and total bone area across growth. Load-to-strength ratio was 26% to 27% lower in boys at all ages, indicating lower risk of distal forearm fracture compared with girls. Contrary to previous HR-pQCT studies that did not align boys and girls at the same biological age, we did not observe sex differences in Ct.BMD. Boys' superior bone size and strength compared with girls may confer them a protective advantage. However, boys' consistently more porous cortices may contribute to their higher fracture incidence during adolescence. Large prospective studies using HR-pQCT that target boys and girls who have sustained a fracture are needed to verify this. © 2016 American Society for Bone and Mineral Research.

Reexamining the Surfaces of Bone in Boys and Girls During Adolescent Growth: A 12-Year Mixed Longitudinal pQCT Study.

We revisit Stanley Garn's theory related to sex differences in endocortical and periosteal apposition during adolescence using a 12-year mixed longitudinal study design. We used peripheral quantitative computed tomography to examine bone parameters in 230 participants (110 boys, 120 girls; aged 11.0 years at baseline). We assessed total (Tt.Ar, mm(2)), cortical (Ct.Ar, mm(2)), and medullary canal area (Me.Ar, mm(2)), Ct.Ar/Tt.Ar, cortical bone mineral density (Ct.BMD, mg/cm(3)), and polar strength-strain index (SSIp , mm(3)) at the tibial midshaft (50% site). We used annual measures of height and chronological age to identify age at peak height velocity (APHV) for each participant. We compared annual accrual rates of bone parameters between boys and girls, aligned on APHV using a linear mixed effects model. At APHV, boys demonstrated greater Tt.Ar (ratio = 1.27; 95% confidence interval [CI] 1.21, 1.32), Ct.Ar (1.24 [1.18, 1.30]), Me.Ar (1.31 [1.22, 1.40]), and SSIp (1.36 [1.28, 1.45]) and less Ct.Ar/Tt.Ar (0.98 [0.96, 1.00]) and Ct.BMD (0.97 [0.96, 0.97]) compared with girls. Boys and girls demonstrated periosteal bone formation and net bone loss at the endocortical surface. Compared with girls, boys demonstrated greater annual accrual rates pre-APHV for Tt.Ar (1.18 [1.02, 1.34]) and Me.Ar (1.34 [1.11, 1.57]), lower annual accrual rates pre-APHV for Ct.Ar/Tt.Ar (0.56 [0.29, 0.83]) and Ct.BMD (-0.07 [-0.17, 0.04]), and similar annual accrual rates pre-APHV for Ct.Ar (1.10 [0.94, 1.26]) and SSIp (1.14 [0.98, 1.30]). Post-APHV, boys demonstrated similar annual accrual rates for Ct.Ar/Tt.Ar (1.01 [0.71, 1.31]) and greater annual accrual rates for all other bone parameters compared with girls (ratio = 1.23 to 2.63; 95% CI 1.11 to 3.45). Our findings support those of Garn and others of accelerated periosteal apposition during adolescence, more evident in boys than girls. However, our findings challenge the notion of greater endocortical apposition in girls, suggesting instead that girls experience diminished endocortical resorption compared with boys.