Bone mineral response to a 7-month randomized controlled, school-based jumping intervention in 121 prepubertal boys: associations with ethnicity and body mass index

Short-termed changes in quantitative ultrasound estimated bone density among young men in an 18-weeks follow-up during their basic training for the Swiss Armed Forces

Background

Quantitative Ultrasound (QUS) methods have been widely used to assess estimated bone density. This study aimed to assess changes in estimated bone density in association with changes in body composition, physical activity, and anthropometry.

Methods

We examined changes in anthropometry, body composition, and physical activity associated with changes in estimated bone mineral density (measured using quantitative ultrasound with a heel ultrasound device indicating broadband ultrasound attenuation BUA and speed of sound SOS) in a follow-up sample of n = 73 young men at the beginning and again 18 weeks later at the end of basic military training.

Results

At the end of the basic training, the subjects were on average significantly heavier (+1.0%), slightly taller (+0.5%) and had a higher fat mass (+6.6%) and grip strength (+8.6%). A significant decrease in mean physical activity (-49.5%) and mean estimated bone density calculated with BUA (-7.5%) was observed in the paired t-test. The results of the multivariable linear regressions (backward selection) show that changes in skeletal muscle mass (delta = 2nd measurement minus 1st measurement) have negative and body weight (delta) have positive association with the speed of sound SOS (delta), while fat mass (delta) and physical activity (delta) had the strongest negative associations with estimated bone mineral density (delta). In particular, we found a negative association between fat mass (delta) and estimated bone mineral density (delta, estimated with BUA).

Conclusion

Our study suggests that estimated bone density from the calcaneus can change within a few months even in young and mostly healthy individuals, depending upon physical activity levels and other co-factors. Further studies including other troop types as control groups as well as on women should follow in order to investigate this public health relevant topic in more depth. To what extent the estimated bone density measurement with quantitative ultrasound is clinically relevant needs to be investigated in further studies.

Peak Loads Associated With High-Impact Physical Activities in Children

Physical activities involving impact loading are important for improving bone strength and mineral density in children. There is little research quantifying impact loads associated with various high-impact activities.

PURPOSE

Examine the magnitude of peak ground reaction forces (pGRF) across different jumping activities in children.

METHODS

Eight children between 8 and 12 years (9.63 [1.49] y; 1.42 [0.08] m; 33.69 [4.81] kg), performed 5 trials of a broad jump, countermovement jump, jumping jack, leap jump, and drop jump on a force plate. The pGRF were determined during the landing phase of each activity and expressed in units of body weight (BW). A repeated-measures analysis of variance was employed to assess differences in pGRF across activities.

RESULTS

Drop jump exhibited the greatest pGRF (3.09 [0.46] BW) in comparison with the vertical jumping jack (2.56 [0.21] BW; P < .001) and countermovement jump (2.45 [0.22] BW; P = .001), as well as the horizontal broad jump (2.25 [0.2] BW; P = .003), and leap jump (2.01 [0.1] BW; P = .002).

CONCLUSION

Peak loads between 2 and 3.1 BW were exhibited across each jump activity, which is moderate compared with magnitudes in most jump interventions seeking to improve bone health. All conditions except drop jump exhibited loading <3 BW, suggesting these activities may not produce sufficient loads to improve bone outcomes.

Exercise in school Physical Education increase bone mineral content and density: Systematic review and meta-analysis

ABSTRACTThis systematic review and meta-analysis aimed to evaluate the effectiveness of interventions through Physical Education (PE) exercises on bone mineral content (BMC) and density (BMD) of children and adolescents. The research was conducted using the online electronic databases PubMed, Science Direct, Web of Science and Scopus (March 2021). The analysis was restricted to school-based studies that examined the effect of PE interventions on BMC and BMD in schoolchildren (<18 years old). Standardised mean differences (SMD) with 95% confidence interval (CI) and random-effects models were calculated. The heterogeneity and inconsistency of the studies were estimated using Cochran's Q-statistic and I², respectively. Twenty-two studies with 2,556 participants were selected. PE interventions were associated with a significant increase in BMC (SMD = 1.348; 95% CI, 1.053-1.643) and BMD (SMD = 0.640; 95% CI, 0.417-0.862). Femoral neck subgroup analysis indicate an increase in BMC for boys (SMD = 1.527; 95% CI, 0.990-2.065) and girls (SMD = 1.27; 95% CI, 0.782-1.767), and in BMD for boys (SMD = 0.518; 95% CI, 0.064-0.972) and girls (SMD = 0.817; 95% CI, 0.349-1.284). Finally, increases are reported in the lumbar spine BMC for boys (SMD = 1.860; 95% CI, 1.018-2.700) and girls (SMD = 1.275; 95% CI, 0.782-1.767). This meta-analysis provides insights into the effectiveness of interventions aimed at including physical exercise in PE on bone mass, suggesting that increasing the proportion of curriculum time allocated to PE may improve students' BMD and BMC, especially in the femoral neck and lumbar spine.

The Effects of Football Practice on Nutritional Status and Body Composition in Children: A Systematic Review and Meta-Analysis

Dietary patterns, exercise, sport, and physical activity have been shown to improve body composition in children. This systematic review with meta-analysis analyzed the effects of practicing football on body composition (fat mass, lean body mass, and bone mineral content) in children. An initial search in PubMed, Web of Science, and SPORTDiscus was carried out in April 2021 to identify relevant articles. Inclusion criteria required children up to 12 years of age with a minimum football intervention duration of 10 weeks. Methodological quality of the articles was evaluated using the PEDro scale. Between the 1803 articles originally founded, only 14 articles were included in the meta-analysis. A total of 1643 subjects between the 14 studies were identified. The review and meta-analysis were conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and used Review Manager and Full Meta-Analysis software. The results between the control and experimental groups showed significantly better lean body mass and fat mass values in the experimental group (p < 0.05). Football practice was positively associated with increases in lean body mass (mean difference of 1.55; 95% CI, 0.96, 2.15), decreases in fat mass (mean difference of -0.81; 95% CI, -1.49, -0.13), and increases in whole body bone mineral content (mean difference of 117.68; 95% CI, 83.69, 151.67). In conclusion, the results of this systematic review with meta-analysis suggest that football positively affects body composition in children. However, further research is needed to confirm the results for bone mineral content.

The Relationships Between Skeletal Muscle Index and Bone Variables in a Group of Young Adults

The purpose of this study was to investigate the relationships between skeletal muscle index (SMI) and bone variables in a group of young adults. Three hundred and thirty-five young adults (129 men and 206 women) whose ages ranged from 18 to 35 yr voluntarily participated in this study. Weight and height were measured, and body mass index (BMI) was calculated. Body composition, bone mineral content (BMC), bone mineral density (BMD), geometric indices of hip bone strength and trabecular bone score (TBS) were determined for each individual by Dual-energy X-ray absorptiometry (DXA). Appendicular skeletal mass (ASM, in kg) was calculated by summing the muscle masses of the 4 limbs, assuming that all nonfat and nonebone mass is skeletal muscle. Skeletal muscle index (SMI) was defined as ASM/height². In young men, SMI was positively correlated to WB BMC (r = 0.63; p < 0.001), WB BMD (r = 0.53; p < 0.001), L1-L4 BMC (r = 0.33; p < 0.001), L1-L4 BMD (r = 0.30; p < 0.001), L1-L4 TBS (r = 0.26; p < 0.01), TH BMC (r = 0.61; p < 0.001), TH BMD (r = 0.46; p < 0.001), FN BMC (r = 0.51; p < 0.001), FN BMD (r = 0.46; p < 0.001), FN cross-sectional area (CSA) (r = 0.56; p < 0.001), FN cross-sectional moment of inertia (CSMI) (r = 0.52; p < 0.001) and FN section modulus (Z) (r = 0.54; p < 0.001) but negatively correlated to FN strength index (SI) (r = -0.24; p < 0.01). In young women, SMI was positively correlated to WB BMC (r = 0.61; p < 0.001), WB BMD (r = 0.60; p < 0.001), L1-L4 BMC (r = 0.35; p < 0.001), L1-L4 BMD (r = 0.33; p < 0.001), L1-L4 TBS (r = 0.29; p < 0.001), TH BMC (r = 0.61; p < 0.001), TH BMD (r = 0.53; p < 0.001), FN BMC (r = 0.45; p < 0.001), FN BMD (r = 0.49; p < 0.001), FN CSA (r = 0.60; p < 0.001), FN CSMI (r = 0.52; p < 0.001), and FN Z (r = 0.40; p < 0.001) but negatively correlated to FN SI (r = -0.20; p < 0.01). The current study suggests that SMI is a positive determinant of bone mineral density and geometric indices of hip bone strength in young adults.

Designing Exercise to Improve Bone Health Among Individuals With Cerebral Palsy

PURPOSE

Individuals with cerebral palsy (CP), ambulatory or not, have less bone strength and density than their peers. Aging individuals with CP are at a higher risk for nontraumatic fractures, progressive deformity, pain, and spinal stenosis. Critical periods for skeletal formation are during prepuberty and adolescence. Applying mechanostat theory to exercise design for individuals with CP may be beneficial.

METHODS

Principles of mechanostat theory, particularly the osteogenic index, is applied to guide the design of exercise programs based on varying levels of physical capacity.

RESULTS

Recommendations are made for optimizing dosing of a variety of interventions for improving bone health among individuals with CP based on mechanostat theory with specific type, number of repetitions, and frequency.

CONCLUSIONS

Researchers and clinicians are called to action to consider the role of exercise throughout the lifespan for all individuals with CP, regardless of level of severity.

The effect of an online exercise programme on bone health in paediatric cancer survivors (iBoneFIT): study protocol of a multi-centre randomized controlled trial

BACKGROUND

New approaches on paediatric cancer treatment aim to maintain long-term health. As a result of radiotherapy, chemotherapy or surgery, paediatric cancer survivors tend to suffer from any chronic health condition. Endocrine dysfunction represents one of the most common issues and affects bone health. Exercise is key for bone mass accrual during growth, specifically plyometric jump training. The iBoneFIT study will investigate the effect of a 9-month online exercise programme on bone health in paediatric cancer survivors. This study will also examine the effect of the intervention on body composition, physical fitness, physical activity, calcium intake, vitamin D, blood samples quality of life and mental health.

METHODS

A minimum of 116 participants aged 6 to 18 years will be randomized into an intervention (n = 58) or control group (n = 58). The intervention group will receive an online exercise programme and diet counselling on calcium and vitamin D. In addition, five behaviour change techniques and a gamification design will be implemented in order to increase the interest of this non-game programme. The control group will only receive diet counselling. Participants will be assessed on 3 occasions: 1) at baseline; 2) after the 9 months of the intervention; 3) 4 months following the intervention. The primary outcome will be determined by dual energy X-ray absorptiometry (DXA) and the hip structural analysis, trabecular bone score and 3D-DXA softwares. Secondary outcomes will include anthropometry, body composition, physical fitness, physical activity, calcium and vitamin D intake, blood samples, quality of life and mental health.

DISCUSSION

Whether a simple, feasible and short in duration exercise programme can improve bone health has not been examined in paediatric cancer survivors. This article describes the design, rationale and methods of a study intended to test the effect of a rigorous online exercise programme on bone health in paediatric cancer survivors. If successful, the iBoneFIT study will contribute to decrease chronic health conditions in this population and will have a positive impact in the society.

TRIAL REGISTRATION

Prospectively registered in isrctn.com: isrctn61195625 . Registered 2 April 2020.

The impact of diet, body composition, and physical activity on child bone mineral density at five years of age-findings from the ROLO Kids Study

Bone health is extremely important in early childhood because children with low bone mineral density (BMD) are at a greater risk of bone fractures. While physical activity and intake of both calcium and vitamin D benefit BMD in older children, there is limited research on the determinants of good bone health in early childhood. The aim of this cross-sectional study was to investigate the impact of diet, physical activity, and body composition on BMD at five years of age. Dietary intakes and physical activity levels were measured through questionnaires. Whole body BMD was measured by dual-energy X-ray absorptiometry in 102 children. Child weight, height, circumferences, skinfolds and serum 25-hydroxyvitamin D (25OHD) concentrations were assessed. There was no association between BMD and dietary calcium, dietary vitamin D, 25OHD, physical activity, or sedentary behaviour. Several measures of body composition were significantly positively associated with BMD; however, neither fat mass nor lean body mass was associated with BMD.Conclusion: Although we found no association between self-reported dietary and lifestyle factors and bone health in early years, increased body size was linked with higher BMD. These findings are important as identifying modifiable factors that can improve bone health at a young age is of utmost importance.What is Known:• Bone health is extremely important in early childhood, as children with low bone mineral density (BMD) are at greater risk of bone fractures.• Physical activity has been found to be beneficial for bone health in adolescents, and body composition has also been associated with BMD in teenage years.• Limited research on the determinants of good bone health in early childhood.What is New:• No association between self-reported lifestyle and dietary factors with bone health in early childhood.• Increased body size was associated with higher BMD at five years of age.

Do teenagers return to normal physical activity levels after limb fractures? A longitudinal, accelerometry-based, activity monitoring study

PURPOSE

This study aimed to elucidate whether levels of physical activity (PA) return to normal after bone healing or whether long-term behavioural changes in PA are to be expected in children and teenagers who have sustained limb fractures.

METHODS

In all, 100 children and teenagers with a first episode of limb fracture and 100 sex- and age-matched healthy controls (CTRL) were recruited for a prospective study. PA in limb fracture patients was assessed at 18-month follow-up using accelerometer measurements, and values were compared with those of CTRL. Time spent in PA at different levels of intensity was determined for each participant and expressed in minutes and as a percentage of total validly measured time.

RESULTS

Mean levels of PA at different levels of intensity by previously injured children and teenagers were similar than CTRL (42 sets of paired data). However, time spent in moderate-to-vigorous PA (MVPA) was lower than 60 minutes among limb-fracture patients at 18-month follow-up.

CONCLUSION

The amount of skeletal loading in children and teenagers returns to normal values by 18 months after limb fracture. Even if time spent in MVPA is not significantly lower in children and teenagers with limb fractures, it no longer reached the international recommendations for school-aged children (MVPA > 60 minutes), which may be interpreted as a lifestyle modification or a behavioural change to avoid new trauma.

LEVEL OF EVIDENCE

II.

Bone Health in Children and Youth with Cystic Fibrosis: A Systematic Review and Meta-Analysis of Matched Cohort Studies

OBJECTIVE

To assess the evidence regarding the differences in areal bone mineral density (aBMD) between children and adolescents with cystic fibrosis (CF) compared with their healthy peers, based on data from longitudinal studies.

STUDY DESIGN

We searched MEDLINE, SPORTDiscus, the Cochrane Library, PEDro (Physiotherapy Evidence Database), and Embase databases. Observational studies addressing the change of aBMD in children with CF and healthy children and adolescents were eligible. The DerSimonian and Laird method was used to compute pooled estimates of effect sizes (ES) and 95% CIs for the change of whole body (WB), lumbar spine (LS), and femoral neck (FN) aBMD.

RESULTS

Six studies with participants with CF and 26 studies with healthy participants were included in the systematic review and meta-analysis. For the analysis in children with CF, the pooled ES for the change of WB aBMD was 0.29 (95% CI -0.15 to 0.74), for the change of LS aBMD was 0.13 (95% CI -0.16 to 0.41), and for the change of FN aBMD was 0.09 (95% CI -0.39 to 0.57). For the analysis in healthy children, the pooled ES for the change of WB aBMD was 0.37 (95% CI 0.26-0.49), for the change of LS aBMD was 0.13 (95% CI -0.16 to 0.41), and for the change of FN aBMD was 0.52 (95% CI 0.19-0.85).

CONCLUSIONS

aBMD development might not differ between children and adolescents with CF receiving medical care compared with their healthy peers. Further longitudinal studies in a CF population during growth and development are required to confirm our findings.

Position Statement: Exercise Guidelines to Increase Peak Bone Mass in Adolescents

Background

An increase in bone mineral density during adolescence increases resistance to fractures in older age. The Korean Society for Bone and Mineral Research and the Korean Society of Exercise Physiology developed exercise guidelines to increase the peak bone mass (PBM) in adolescents based on evidence through a systematic review of previous research.

Methods

Articles were selected using the systematic method, and the exercise guidelines were established by selecting key questions (KQs) and defining the effects of exercises based on evidence through a literature review for selecting the final exercise method. There were 9 KQs. An online search was conducted on articles published since 2000, and 93 articles were identified.

Results

An increase in PBM in adolescence was effective for preventing osteoporosis and fractures in older age. Exercise programs as part of vigorous physical activity (VPA) including resistance and impact exercise at least 5 to 6 months were effective for improving PBM in adolescents. It is recommended that resistance exercise is performed 10 to 12 rep·set⁻¹ 1-2 set·region⁻¹ and 3 days·week⁻¹ using the large muscles. For impact exercises such as jumping, it is recommended that the exercise is performed at least 50 jumps·min⁻¹, 10 min·day⁻¹ and 2 days·week⁻¹.

Conclusions

Exercise guidelines were successfully developed, and they recommend at least 5 to 6 months of VPA, which includes both resistance and impact exercises. With the development of exercise guidelines, the incidence of osteoporosis and fractures in the aging society can be reduced in the future, thus contributing to improved public health.

Bone mineral density in an urban and a rural children population-A comparative, population-based study in Enugu State, Nigeria

INTRODUCTION

Osteoporosis is one of the non-communicable diseases linked to urbanisation. The foundation of osteoporotic fractures stems from childhood. Therefore, studies that promote maximising peak bone mass are strongly advocated. Studies have shown that there are differences in the incidence of osteoporotic fractures in rural and urban communities. No study has investigated urban-rural differences in BMD of Nigerian children. This study, therefore, aimed to investigate urban-rural differences in BMD of Nigerian children and the association with physical activity, demographic and anthropometric variables.

METHODS

In a cross-sectional, study in Enugu, Nigeria, estimated bone mineral density (eBMD) was measured at the calcaneum using the QUS densitometer, Hologic Sahara, in 457 urban (Enugu metropolis) and 559 rural (Nsukka community) children aged 6-14 years. Height, weight and physical activity were measured. Independent sample t-test was used for comparative analysis while Pearson correlation coefficients and multiple regression models were used to examine the relationship between the eBMD and the other parameters.

RESULTS

The mean (S.D) eBMD of the urban children [0.52(0.09) g/cm²] were significantly higher (p < 0.05) than their age- and gender-matched counterparts in the rural areas [0.51(0.08) g/cm²]. Age and weight predicted (p < 0.05) the eBMD in the urban subjects while only age was the predictor (p < 0.05) in the rural subjects. The physical activity pattern had no relationship with eBMD in both urban and rural children in Enugu, Nigeria.

CONCLUSIONS

The eBMD of rural children is lower than that of their age- and gender-matched urban counterparts.

Does Muscular Power Predict Bone Mineral Density in Young Adults?

The aim of this study was to explore the relationships between maximum power and bone variables in a group of young adults. Two hundred and one young adults (53 men and 148 women) whose ages range from 18 to 35 years voluntarily participated in this study. Weight and height were measured, and body mass index was calculated. Body composition, bone mineral content (BMC) and bone mineral density (BMD) were determined for each individual by dual-energy X-ray absorptiometry. Vertical jump was evaluated using a validated field test (Sargent test). The highest vertical jump was selected. Maximum power (P max, in watts) of the lower limbs was calculated accordingly. In young men, maximum power was positively correlated to whole body (WB) BMC (r = 0.65; p < 0.001), WB BMD (r = 0.41; p < 0.01), L1-L4 BMC (r = 0.54; p < 0.001), total hip (TH) BMC (r = 0.50; p < 0.001), femoral neck (FN) BMC (r = 0.35; p < 0.01), FN cross-sectional area (CSA) (r = 0.33; p < 0.05) and FN cross-sectional moment of inertia (CSMI) (r = 0.50; p < 0.001). In young women, maximum power was positively correlated to WB BMC (r = 0.48; p < 0.001), WB BMD (r = 0.28; p < 0.001), L1-L4 BMC (r = 0.34; p < 0.001), TH BMC (r = 0.43; p < 0.001), TH BMD (r = 0.21; p < 0.01), FN BMC (r = 0.42; p < 0.001), FN BMD (r = 0.31; p < 0.001), FN CSA (r = 0.41; p < 0.001), FN CSMI (r = 0.40; p < 0.001) and FN Z (r = 0.41; p < 0.01). The current study suggests that maximum power is a positive determinant of WB BMC, WB BMD, FN CSA, and FN CSMI in young men. It also shows that maximum power is a positive determinant of WB BMC, WB BMD, TH BMD, FN BMD, FN CSA, FN CSMI, and FN Z in young women.

A 9-Month Jumping Intervention to Improve Bone Geometry in Adolescent Male Athletes

PURPOSE

Sports have different effects on bone development and effective interventions to improve bone health of adolescent athletes are needed. The purpose of the study was to investigate the effect of a 9-month jumping intervention on bone geometry and metabolism in adolescent male athletes.

METHODS

Ninety-three adolescent (14.1 yr old) male swimmers (SWI), footballers (FOO), and cyclists (CYC) were randomized to intervention and sport (INT-SWI = 19, INT-FOO = 15, and INT-CYC = 14) or sport only (CON-SWI = 18, CON-FOO = 15, and CON-CYC = 12) groups. Cross-sectional area, cross-sectional moment of inertia (CSMI), and section modulus (Z) at the femoral neck were assessed using hip structural analysis and trabecular texture of the lumbar spine using trabecular bone score. Bone mineral content (BMC) at femoral neck and lumbar spine was assessed using dual-energy x-ray absorptiometry. Serum N-terminal propeptide of procollagen type I, isomer of the carboxy-terminal telopeptide of type 1 collagen, total serum calcium, and 25-hydroxyvitamin D were analyzed.

RESULTS

INT-CYC acquired significantly higher lumbar spine BMC (4.6%) and femoral neck BMC (9.8%) than CON-CYC. INT-CYC acquired significantly higher cross-sectional area (11.0%), CSMI (10.1%), and trabecular bone score (4.4%) than CON-CYC. INT-SWI acquired significantly higher femoral neck BMC (6.0%) and CSMI (10.9%) than CON-SWI. There were no significant differences between INT-FOO and CON-FOO in any bone outcomes. N-terminal propeptide of procollagen type I significantly decreased in CON-SWI, INT-FOO, CON-FOO, and CON-CYC. Carboxy-terminal telopeptide of type 1 collagen significantly decreased in CON-SWI and CON-CYC. The 25-hydroxyvitamin D significantly increased in INT-CYC, CON-CYC, INT-FOO, and CON-FOO.

CONCLUSIONS

A 9-month jumping intervention improved bone outcomes in adolescent swimmers and cyclists, but not in footballers. This intervention might be used by sports clubs to improve bone health of adolescent athletes.

School-based exercise interventions effectively increase bone mineralization in children and adolescents

Osteoporosis and fragility fractures have become major global public health concerns, and they can be prevented by maximizing peak bone mass during childhood and adolescence with weight-bearing physical activity, which can result in stronger and healthier bones that significantly decrease the risk of osteoporosis and fragility fractures in adulthood and the elderly years. From a public health perspective, implementing weight-bearing physical activity for children and adolescents is best achieved with school-based exercise interventions, and a review of school-based exercise interventions was conducted to determine their effectiveness in increasing bone mineral density (BMD) and/or bone mineral content (BMC). Seventeen studies were reviewed, all school-based exercise interventions utilized jumping exercises, and 15 of the 17 studies found at least one significant increase in measures of BMD and/or BMC for the total body, and/or at the hip, vertebrae, and/or wrist. One study that found no significant differences did report significant increases in bone structural strength, and the other study with no significant differences had exercises that measured and reported the lowest ground reaction forces (GRFs) of only 2–3 times body weight (BW), whereas the other studies that showed significant increase(s) in BMD and/or BMC had exercise with measured and reported GRFs ranging from 3.5 × to 8.8 × BW. School-based exercise interventions are time- and cost-efficient and effective in increasing BMD and/or BMC in children and adolescents, but must incorporate high-intensity exercise, such as high-impact jumping of sufficient GRFs, in order to significantly increase bone mineralization for osteoporosis and fragility fracture prevention later in life.

Exercise Early and Often: Effects of Physical Activity and Exercise on Women's Bone Health

In 2011 over 1.7 million people were hospitalized because of a fragility fracture, and direct costs associated with osteoporosis treatment exceeded 70 billion dollars in the United States. Failure to reach and maintain optimal peak bone mass during adulthood is a critical factor in determining fragility fracture risk later in life. Physical activity is a widely accessible, low cost, and highly modifiable contributor to bone health. Exercise is especially effective during adolescence, a time period when nearly 50% of peak adult bone mass is gained. Here, we review the evidence linking exercise and physical activity to bone health in women. Bone structure and quality will be discussed, especially in the context of clinical diagnosis of osteoporosis. We review the mechanisms governing bone metabolism in the context of physical activity and exercise. Questions such as, when during life is exercise most effective, and what specific types of exercises improve bone health, are addressed. Finally, we discuss some emerging areas of research on this topic, and summarize areas of need and opportunity.

Physical Performance Variables and Bone Mineral Density in a Group of Young Overweight and Obese Men

The aim of this study was to explore the relationships between performances obtained in different physical tests and bone parameters (bone mineral density [BMD], bone mineral content, hip geometry indices, and trabecular bone score [TBS]) in a group of young Lebanese overweight and obese adult men. Fifty-two overweight and/or obese (body mass index > 25 kg/m²) young men whose ages range from 18 to 35 yr participated in this study. Weight and height were measured, and body mass index was calculated. Body composition, BMD, cross-sectional area and section modulus (Z) of the femoral neck (FN), and TBS were measured by dual-energy X-ray absorptiometry. Maximum oxygen consumption (VO₂ max, in liter per minute) was determined by direct measurement while exercising on a medical treadmill. One-repetition-maximum half-squat and maximum power (P max) of the lower limbs were measured using validated exercises. Lean mass was a positive determinant of whole-body bone mineral content (r = 0.71, p < 0.001), FN cross-sectional area (r = 0.51, p < 0.001), and FN Z (r = 0.58, p < 0.001). VO₂ max (in liter per minute) was a positive determinant of whole-body BMD (r = 0.47, p < 0.001), total hip BMD (r = 0.43, p < 0.01), and FN BMD (r = 0.42, p < 0.01). VO₂ max (in milliliter per minute per kilogram) was a positive determinant of TBS (r = 0.30, p < 0.05). One repetition maximum was a positive determinant of L1-L4 BMD (r = 0.33, p < 0.05). This study suggests that VO₂ max (in liter per minute) is a positive determinant of BMD, and VO₂ max (in milliliter per minute per kilogram) is a positive determinant of TBS in overweight and obese men.

The effect of a high-impact jumping intervention on bone mass, bone stiffness and fitness parameters in adolescent athletes

This study demonstrates that a 9-month jumping intervention can improve bone mass gains and physical fitness performance in adolescent males participating in non-osteogenic sports, such as swimming and cycling.

PURPOSE

To examine the effect of a jumping intervention on bone mass, bone stiffness and fitness parameters in adolescents involved in different sports.

METHODS

Ninety-three adolescent male swimmers (SWI), footballers (FOO) and cyclists (CYC) were randomised to intervention (INT) and sport (INT-SWI = 19, INT-FOO = 15, INT-CYC = 14) or sport only (CON-SWI = 18, CON-FOO = 15, CON-CYC = 12) groups. The 9-month jumping intervention consisted of 3 levels (12 weeks each) of 20 repetitions per set of counter movement jumps (CMJ) using adjustable weight vests (level 1 = 20 CMJ jumps/set, 0 kg, 3 sets/day, 3 times/week; level 2 = 20 CMJ jumps/set, 2 kg, 4 sets/day, 3 times/week; level 3 = 20 CMJ jumps/set, 5 kg, 4 sets/day, 4 times/week). Total body bone mineral content (BMC) at total body less head (TBLH) was measured using dual-energy X-ray absorptiometry and bone stiffness using quantitative ultrasound. Fitness was assessed using the 20-m shuttle run (20mSRT), CMJ and standing long jump (SLJ) tests.

RESULTS

INT-SWI had significantly higher increase in BMC legs and bone stiffness compared to CON-SWI (4.2-12.7%). INT-CYC had significantly higher increase in BMC at TBLH and legs and bone stiffness compared to CON-CYC (5.0-12.3%). There were no significant differences between INT-FOO and CON-FOO in any bone outcomes (0.9-3.9%). The increase in CMJ performance was significantly higher in INT-SWI (3.1 cm) and INT-CYC (3.2 cm) compared to CON-SWI and CON-CYC groups, respectively.

CONCLUSIONS

A 9-month jumping intervention can improve bone mass, bone stiffness and muscular fitness in adolescent males participating in non-osteogenic sports, such as swimming and cycling.

CLINICAL TRIAL REGISTRATION

ISRCTN17982776.

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.

Investigating the Prevalence of Low Bone Mass in Children of Southern Iran and Its Associated Factors

BACKGROUND

Improving peak bone mass and bone strength in the first years of life and enhancing it during young adulthood could prevent osteoporosis and fractures in the last years of life. We evaluated the prevalence of low bone mass in the lumbar and femoral neck and its associated factors in southern Iranian children.

METHODS

This is a cross-sectional study on healthy Iranian children aged 9 - 18 years old during 2011 - 2012. Dual energy X-ray absorptiometry (DEXA) was used for measuring bone mineral density (BMD). BMD Z-score ≤ -2 was considered as low. Anthropometric data, physical activity, sun exposure, puberty, and mineral biochemical parameters were assessed. Data were analyzed using SPSS v.15.

RESULTS

477 normal children, including 236 (49.5%) girls and 241 (50.5%) boys, aged 13.8 ± 2.7 years were enrolled. Prevalence of low bone mass (LBM) in the femoral and lumbar region was 10.7% and 18.7%, respectively. The prevalence of LBM in femur of girls is twice more than boys. Fat mass index, BMI Z-score, and physical activity were associated with lumbar low bone mass. BMI Z-score and physical activity were associated with femoral low bone mass.

CONCLUSIONS

High prevalence of low bone mineral density in children 9 to 18 years in south of the country is concerned and is needed to plan for prevention and treatment. BMI-Z score, fat mass index, and physical activity were the 3 most important preventive factors in developing low bone mass in children.

Tibial impact accelerations in gait of primary school children: The effect of age and speed

Tibial stress fractures are associated with increased lower extremity loading at initial foot-ground contact, reflected in high peak positive acceleration (>8g) of the tibia in adults. There is no reported data on peak positive acceleration of the tibia in children during walking and running. The aim of this study was to establish tibial peak positive acceleration responses in children across a range of age and gait speeds. Twenty-four children aged 8.5±1.4years with no known gait pathology comprised two age groups; Young (7-9year, n=12) and Older (10-12 years, n=12). Wireless Inertial Measurement Unit comprising a tri-axial accelerometer was securely taped to the anteromedial aspect of the distal tibia to measure peak positive acceleration responses while walking and running on the treadmill at 3 different speeds (20% below baseline, baseline, and 20% above baseline). Results showed significant increase in peak positive acceleration with increased gait speed and greater variability in young children compared to older children. The study suggests that ground impact in walking, but not running, is mature by age 7 years. Future studies should explore strategies using peak positive acceleration responses to monitor ground impact during sport activities and its application in gait retraining.

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.

Plyometric exercise and bone health in children and adolescents: a systematic review

BACKGROUND

Many jumping interventions have been performed in children and adolescents in order to improve bone-related variables and thus, ensure a healthy bone development during these periods and later in life. This systematic review aims to summarize and update present knowledge regarding the effects that jumping interventions may have on bone mass, structure and metabolism in order to ascertain the efficacy and durability (duration of the effects caused by the intervention) of the interventions.

DATA SOURCES

Identification of studies was performed by searching in the database MEDLINE/PubMed and SportDiscus. Additional studies were identified by contacting clinical experts and searching bibliographies and abstracts. Search terms included "bone and bones", "jump*", "weight-bearing", "resistance training" and "school intervention". The search was conducted up to October 2014. Only studies that had performed a specific jumping intervention in under 18-year olds and had measured bone mass were included. Independent extraction of articles was done by 2 authors using predefined data fields.

RESULTS

A total of 26 studies were included in this review. Twenty-four studies found positive results as subjects included in the intervention groups showed higher bone mineral density, bone mineral content and bone structure improvements than controls. Only two studies found no effects on bone mass after a 10-week and 9-month intervention. Moreover, those studies that evaluated the durability of the effects found that some of the increases in the intervention groups were maintained after several years.

CONCLUSIONS

Jumping interventions during childhood and adolescence improve bone mineral content, density and structural properties without side effects. These type of interventions should be therefore implemented when possible in order to increase bone mass in early stages of life, which may have a direct preventive effect on bone diseases like osteoporosis later in life.

Bone Variables in Active Overweight/Obese Men and Sedentary Overweight/Obese Men

The aim of this study was to compare bone variables in active overweight/obese men and sedentary overweight/obese men. Thirty-seven active overweight/obese men and 45 sedentary overweight/obese men participated in this study. Weight and height were measured, and body mass index was calculated. Body composition and bone variables (bone mineral content [BMC], bone mineral density [BMD], geometric indices of hip bone strength, and trabecular bone score) were measured by DXA. Physical activity level, daily calcium intake, daily protein intake, and sleep duration were measured by validated questionnaires. Maximum oxygen consumption (VO₂ max) was determined by direct measurement while exercising on a medical treadmill. One-repetition-maximum half-squat of the lower limbs was measured using a validated protocol. Body weight and body mass index were higher in sedentary overweight/obese men than in active overweight/obese men. In the whole population (n = 82), VO₂ max (in liter per minute), lean mass, and one-repetition-maximum half-squat were positively correlated to BMC, BMD, and geometric indices of hip bone strength (cross-sectional area and section modulus [Z] of the femoral neck [FN]). After adjusting for body weight using a 1-way analysis of covariance, active overweight/obese men displayed higher whole-body BMC, lumbar spine BMD, total hip BMD, FN BMD, FN cross-sectional area, and FN Z values than sedentary overweight/obese men. In conclusion, the current study suggests that physical activity level positively affects bone variables in overweight/obese men. Optimizing lean mass and muscular strength of the lower limbs can help to prevent osteoporosis in overweight and obese men.

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.

No difference in the level of physical activity between children who have or have never sustained a fracture

This study investigates whether children with an acute fracture have a different level of physical activity compared to children who have never sustained a fracture, as measured by the Physical Activity Questionnaire for older children (PAQ-C). The PAQ-C scores of 683 children (295 girls) aged 6-12 years (mean age 9.4 years) who presented to our institution with an acute fracture were compared to the PAQ-C scores of 151 random children (81 girls) aged 6-12 years (mean 9.1 years) in the same area who had never sustained a fracture. Multivariate regression analysis was employed, controlling for age and gender. The mean PAQ-C score of the children who presented to the institution with an acute fracture was 2.85 (95% confidence interval [CI], 2.80-2.91). For the children who had never sustained a fracture, the mean PAQ-C score was 2.78 (95% CI, 2.69-2.87). If there is a true difference in the level of physical activity between children who have or have never sustained a fracture, the PAQ-C questionnaire is not sensitive enough to identify it.

Positive effects on bone mineralisation and muscular fitness after 10 months of intense school-based physical training for children aged 8-10 years: the FIT FIRST randomised controlled trial

OBJECTIVES

We investigated whether musculoskeletal fitness of school children aged 8-10 years was affected by frequent intense PE sessions.

DESIGN AND PARTICIPANTS

295 Danish school children aged 8-10 years were cluster randomised to a small-sided ball game group (SSG) (n=96, four schools, five classes), a circuit strength training group (CST) (n=83, four schools, four classes) or a control group (CON, n=116, two schools, five classes).

INTERVENTION

SSG or CST was performed 3×40 min/week over 10 months. Whole-body dual-energy X-ray absorptiometry (DXA) scans were used to determine areal bone mineral density (aBMD), bone mineral content (BMC) and lean body mass (LBM). Flamingo balance, standing long jump and 20-m sprint tests were used to determine muscular fitness.

RESULTS

Analysis of baseline-to-10 months change scores showed between-group differences in favour of the interventions in whole-body aBMD (SSG vs CON: 8 mg/cm², 95% CI 3 to 13; CST vs CON: 7 mg/cm², 95% CI 2 to 13, p<0.05) and leg BMC (SSG vs CON: 11 g, 95% CI 4 to 18; CST vs CON: 11 g, 95% CI 3 to 18, p<0.05). SSG had higher change scores in leg aBMD compared with CON and CST (SSG vs CON: 19 mg/cm², 95% CI 11 to 39, p<0.05; SSG vs CST: 12 mg/cm², 95% CI 3 to 21, p<0.05), and CST had higher change scores in whole-body BMC compared with CON (CST vs CON: 25 g, 95% CI 10 to 39, p<0.05). Both training types resulted in higher change scores in postural balance (SSG vs CON: 2.4 fewer falls/min, 95% CI 0.3 to 4.5, CST vs CON: 3.6 fewer falls/min, 95% CI 1.3 to 5.9, p<0.05) and jump length (SSG vs CON: 10%, 95% CI 5 to 16%; CST vs CON: 9%, 95% CI 3 to 15%, p<0.05). No between-group differences were observed for sprint performance or LBM (p>0.05).

CONCLUSIONS

In conclusion, 3×40 min/week with SSG or CST over a full school year improves bone mineralisation and several aspects of muscular fitness of children aged 8-10 years, suggesting that well-organised intense physical education classes can contribute positively to develop musculoskeletal health in young children.

TRIAL REGISTRATION NUMBER

NCT02000492, post results.

The National Osteoporosis Foundation's position statement on peak bone mass development and lifestyle factors: a systematic review and implementation recommendations

Lifestyle choices influence 20-40 % of adult peak bone mass. Therefore, optimization of lifestyle factors known to influence peak bone mass and strength is an important strategy aimed at reducing risk of osteoporosis or low bone mass later in life. The National Osteoporosis Foundation has issued this scientific statement to provide evidence-based guidance and a national implementation strategy for the purpose of helping individuals achieve maximal peak bone mass early in life. In this scientific statement, we (1) report the results of an evidence-based review of the literature since 2000 on factors that influence achieving the full genetic potential for skeletal mass; (2) recommend lifestyle choices that promote maximal bone health throughout the lifespan; (3) outline a research agenda to address current gaps; and (4) identify implementation strategies. We conducted a systematic review of the role of individual nutrients, food patterns, special issues, contraceptives, and physical activity on bone mass and strength development in youth. An evidence grading system was applied to describe the strength of available evidence on these individual modifiable lifestyle factors that may (or may not) influence the development of peak bone mass (Table 1). A summary of the grades for each of these factors is given below. We describe the underpinning biology of these relationships as well as other factors for which a systematic review approach was not possible. Articles published since 2000, all of which followed the report by Heaney et al. [1] published in that year, were considered for this scientific statement. This current review is a systematic update of the previous review conducted by the National Osteoporosis Foundation [1]. [Table: see text] Considering the evidence-based literature review, we recommend lifestyle choices that promote maximal bone health from childhood through young to late adolescence and outline a research agenda to address current gaps in knowledge. The best evidence (grade A) is available for positive effects of calcium intake and physical activity, especially during the late childhood and peripubertal years-a critical period for bone accretion. Good evidence is also available for a role of vitamin D and dairy consumption and a detriment of DMPA injections. However, more rigorous trial data on many other lifestyle choices are needed and this need is outlined in our research agenda. Implementation strategies for lifestyle modifications to promote development of peak bone mass and strength within one's genetic potential require a multisectored (i.e., family, schools, healthcare systems) approach.

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.

Does Exercise Influence Pediatric Bone? A Systematic Review

BACKGROUND

Periods of growth are thought to be the best time to increase bone mineral content, bone area, and areal bone mineral density (aBMD) through increased loading owing to high rates of bone modeling and remodeling. However, questions remain regarding whether a benefit of exercise is seen at all bone sites, is dependent on pubertal status or sex of the child, or whether other factors such as diet modify the response to exercise.

QUESTIONS/PURPOSES

We asked: (1) Does bone-loading exercise in childhood consistently increase bone mineral content, bone area, or aBMD? (2) Do effects of exercise differ depending on pubertal status or sex? (3) Does calcium intake modify the bone response to exercise?

METHODS

A literature search identified 22 unique trials for inclusion in this meta-analysis of the effect of exercise on bone changes by bone site, pubertal status, and sex. Sample sizes ranged from 16 to 410 subjects 3 to 18 years old with length of intervention ranging from 3 to 36 months. Fifteen of 22 trials were randomized (child randomized in nine, classroom/school randomized in six) and seven were observational trials. Ten trials were Level 2 and 11 were Level 3 based on the Oxford Centre for Evidence-Based Medicine criteria. Random effects models tested the difference (intervention mean effect-control mean effect) in percent change in bone mineral content, bone area, and aBMD. Meta-regression was used to identify sources of heterogeneity and funnel plots were used to assess publication bias.

RESULTS

Children assigned to exercise had greater mean percent changes in bone mineral content and aBMD than children assigned to the control groups. Mean differences (95% CI) in bone mineral content percent change between intervention and control groups at total body (0.8; 95% CI, 0.3-1.3; p = 0.003), femoral neck (1.5; 95% CI, 0.5-2.5; p = 0.003), and spine (1.7; 95% CI, 0.4-3.1; p = 0.01) were significant with no differences in bone area (all p > 0.05). There were greater percent changes in aBMD in intervention than control groups at the femoral neck (0.6; 95% CI, 0.2-1.1; p = 0.006) and spine (1.2; 95% CI, 0.6-1.8; p < 0.001). Benefit of exercise was limited to children who were prepubertal (bone mineral content: total body [0.9; 95% CI, 0.2-1.7; p = 0.01], femoral neck [1.8; 95% CI, 0.0-3.5; p = 0.047], spine [3.7; 95% CI, 0.8-6.6; p = 0.01], and aBMD: femoral neck [0.6; 95% CI, -0.1-1.2; p = 0.07], spine [1.5; 95% CI, 0.7-2.3; p < 0.001]), with no differences among children who were pubertal (all p > 0.05). Changes in aBMD did not differ by sex (all p > 0.05), although the number of studies providing male-specific results was small (six of 22 eligible studies included boys). There was significant heterogeneity in bone mineral content and bone area for which a source could not be identified. Heterogeneity in spine aBMD was reduced by including calcium intake and intervention length as covariates. Three trials designed to determine whether calcium intake modified the bone response to exercise all reported a greater effect of exercise on leg bone mineral content in children randomized to receive supplemental calcium than those receiving placebo.

CONCLUSIONS

Exercise interventions during childhood led to 0.6% to 1.7% greater annual increase in bone accrual, with effects predominantly among children who were prepubertal. If this effect were to persist into adulthood, it would have substantial implications for osteoporosis prevention. It is important to identify sources of heterogeneity among studies to determine factors that might influence the bone response to increased exercise during growth.

LEVEL OF EVIDENCE

Level II, therapeutic study.

Past sporting activity during growth induces greater bone mineral content and enhances bone geometry in young men and women

We aimed to determine the effect of past sporting activity on bone mineral content (BMC), areal bone mineral density (aBMD) in the lumbar spine and proximal femur, and bone geometry of the mid femur in young men and women. We assessed 142 subjects, comprising 79 young men (21.2 ± 0.8 years) and 63 premenopausal young women (21.4 ± 0.6 years). The subjects were classified into three groups, two on the basis of the age of starting to participate in sport [elementary school starters (6-12 years), junior high school to university starters (13-22 years)], and the third group had no participation in sport. We measured BMC and aBMD by dual-energy X-ray absorptiometry (DXA) in the lumbar spine and proximal femur, and bone geometric characteristics of the mid femur by magnetic resonance imaging (MRI), and calculated the osteogenic index (OI) of previous sporting activity. The OI correlated significantly with many MRI-determined measures of bone geometry; DXA-measured BMC and aBMD were effective indicators of previous sporting activity in both sexes. The female elementary school starters had significantly greater femoral mid-diaphyseal perimeters (vs the no-sport group), bone cross-sectional area (vs the 13-22-year-old starters and the no-sport group), and maximum and minimum second moment of area at the mid-diaphysis point of the femur (vs the no-sport group). The OI is a proven practicable and useful index. DXA- and MRI-determined geometric characteristics showed that high-impact, weight-bearing exercise before and in early puberty induces greater total proximal femur BMC and enhances femoral mid-diaphyseal size and shape, and that these benefits persisted in young adult women.

Factors affecting bone mineral mass loss after lower-limb fractures in a pediatric population

BACKGROUND

The purpose of this study was to assess the effects of the durations of cast immobilization and non-weight-bearing periods, and decreases in vigorous physical activity (VPA) on bone mineral parameters in a pediatric population treated for a lower-limb fracture.

METHODS

Fifty children and teenagers who had undergone a cast-mediated immobilization for a leg or ankle fracture were prospectively recruited. The durations of cast immobilization and non-weight-bearing periods were recorded for each participant. Dual-energy x-ray absorptiometry scans were performed at the time of fracture treatment (baseline) and at cast removal. Physical activity during cast immobilization was assessed using accelerometers.

RESULTS

A strong negative correlation was found between the total duration of cast immobilization and decreases in both calcaneal bone mineral density (BMD) (r=-0.497) and total lower-limb bone mineral content (BMC) (r=-0.405). A strong negative correlation was also noted between the durations of the non-weight-bearing periods and alterations in calcaneal BMD (r=-0.420). No apparent correlations were found between lower BMD and BMC and decreased VPA.

CONCLUSIONS

Bone mineral loss was correlated to the total duration of cast immobilization for all measurement sites on the affected leg, whereas it was only correlated to the durations of non-weight-bearing periods for calcaneal BMD and total lower-limb BMC. However, no correlations were noted between bone mineral loss and decreased VPA.

Effect of a program of short bouts of exercise on bone health in adolescents involved in different sports: the PRO-BONE study protocol

BACKGROUND

Osteoporosis is a skeletal disease associated with high morbidity, mortality and increased economic costs. Early prevention during adolescence appears to be one of the most beneficial practices. Exercise is an effective approach for developing bone mass during puberty, but some sports may have a positive or negative impact on bone mass accrual. Plyometric jump training has been suggested as a type of exercise that can augment bone, but its effects on adolescent bone mass have not been rigorously assessed. The aims of the PRO-BONE study are to: 1) longitudinally assess bone health and its metabolism in adolescents engaged in osteogenic (football), non-osteogenic (cycling and swimming) sports and in a control group, and 2) examine the effect of a 9 month plyometric jump training programme on bone related outcomes in the sport groups.

METHODS/DESIGN

This study will recruit 105 males aged 12-14 years who have participated in sport specific training for at least 3 hours per week during the last 3 years in the following sports groups: football (n = 30), cycling (n = 30) and swimming (n = 30). An age-matched control group (n = 15) that does not engage in these sports more than 3 hours per week will also be recruited. Participants will be measured on 5 occasions: 1) at baseline; 2) after 12 months of sport specific training where each sport group will be randomly allocated into two sub-groups: intervention group (sport + plyometric jump training) and sport group (sport only); 3) exactly after the 9 months of intervention; 4) 6 months following the intervention; 5) 12 months following the intervention. Body composition (dual energy X-ray absorptiometry, air displacement plethysmography and bioelectrical impedance), bone stiffness index (ultrasounds), physical activity (accelerometers), diet (24 h recall questionnaire), pubertal maturation (Tanner stage), physical fitness (cardiorespiratory and muscular), bone turnover markers and vitamin D will be measured at each visit.

DISCUSSION

The PRO-BONE study is designed to investigate the impact of osteogenic and non-osteogenic sports on bone development in adolescent males during puberty, and how a plyometric jump training programme is associated with body composition parameters.

Building healthy bones throughout life: an evidence-informed strategy to prevent osteoporosis in Australia

Osteoporosis imposes a tremendous burden on Australia: 1.2 million Australians have osteoporosis and 6.3 million have osteopenia. In the 2007–08 financial year, 82 000 Australians suffered fragility fractures, of which > 17 000 were hip fractures. In the 2000–01 financial year, direct costs were estimated at $1.9 billion per year and an additional $5.6 billion on indirect costs. Osteoporosis was designated a National Health Priority Area in 2002; however, implementation of national plans has not yet matched the rhetoric in terms of urgency. Building healthy bones throughout life, the Osteoporosis Australia strategy to prevent osteoporosis throughout the life cycle, presents an evidence-informed set of recommendations for consumers, health care professionals and policymakers. The strategy was adopted by consensus at the Osteoporosis Australia Summit in Sydney, 20 October 2011. Primary objectives throughout the life cycle are: to maximise peak bone mass during childhood and adolescence to prevent premature bone loss and improve or maintain muscle mass, strength and functional capacity in healthy adults to prevent and treat osteoporosis in order to minimise the risk of suffering fragility fractures, and reduce falls risk, in older people. The recommendations focus on three affordable and important interventions — to ensure people have adequate calcium intake, vitamin D levels and appropriate physical activity throughout their lives. Recommendations relevant to all stages of life include: daily dietary calcium intakes should be consistent with Australian and New Zealand guidelines serum levels of vitamin D in the general population should be above 50nmol/L in winter or early spring for optimal bone health regular weight-bearing physical activity, muscle strengthening exercises and challenging balance/mobility activities should be conducted in a safe environment.

Exercise to improve pediatric bone and fat: a systematic review and meta-analysis

PURPOSE

This study aimed to determine the effects of school-based, bone-focused exercise interventions on bone, fat, and lean mass in children by systematically reviewing and meta-analyzing the literature.

METHODS

Potentially relevant articles were identified by searching electronic databases. Abstracts were included if they described the effects of an in-school exercise intervention for children 5-17 yr old compared with controls and presented baseline and follow-up results for bone, fat, and lean measures. Identified studies were systematically reviewed for methodological quality. Meta-analyses were performed for whole body, lumbar spine, and femoral neck bone mineral content (BMC), fat, and lean mass.

RESULTS

Sixteen eligible trials were identified including eight randomized controlled trials, three clinical controlled trials, and five nonrandomized, nonmatched studies. The quality analysis revealed two studies had low, nine had medium, and five had a high risk of bias. Meta-analyses revealed a small positive effect of bone-targeted exercise on whole body BMC (standardized mean difference [SMD] = 0.483, 95% CI = 0.132-0.833), femoral neck BMC (SMD = 0.292, 95% CI = -0.022 to 0.607), lumbar spine BMC (SMD = 0.384, 95% CI = 0.193-0.575), fat mass (SMD = -0.248, 95% CI = -0.406 to -0.089), and lean mass (SMD = 0.159, 95% CI = -0.076 to 0.394).

CONCLUSIONS

Beneficial effects of school-based, bone-targeted exercise were observed for bone and fat, but not for lean mass. Excluding trials with high risk of bias strengthened that effect. Considerable study heterogeneity may have obscured effects on lean mass. The effects observed for bone and fat support the pursuit of brief, jumping-focused interventions to reduce fat as well as enhance musculoskeletal tissue in school age children.

Effects of weight-bearing activities on bone mineral content and density in children and adolescents: a meta-analysis

Osteoporosis and associated fractures are a major health concern in Western industrialized nations. Exercise during growth is suggested to oppose the involutional bone loss later in life by increasing peak bone mass. The primary aim of the present meta-analysis was to provide a robust estimate of the effect of weight-bearing activities (WBAs) on bone mineral content (BMC) and areal bone mineral density (aBMD), during childhood and adolescence. To locate relevant studies up to June 2012, computerized searches of multiple bibliographic databases and hand searches of key journals and reference lists were performed. Results were extracted by two independent reviewers. The quality of the included trials was assessed via the Physiotherapy Evidence Database (PEDro) score. The study group effect was defined as the difference between the standardized mean change for the treatment and control groups divided by the pooled pretest SD. From 109 potentially relevant studies, only 27 met the inclusion criteria. The analyzed training programs were capable of significantly increasing BMC and aBMD during growth. However, the weighted overall effect sizes (ESs) for changes in BMC (ES 0.17; 95% confidence interval [CI], 0.05-0.29; p < 0.05) and aBMD (ES 0.26; 95% CI, 0.02-0.49) were small. Stepwise backward regression revealed that more than one-third of the observed variance (r(2)  = 0.35) between subgroups of the BMC dataset could be explained by differences in the amount of habitual calcium intake per day (beta 0.54, p < 0.01) and the maturational stage (beta -0.28, p < 0.01) at baseline. No significant moderators were identified for aBMD, possibly due to the small number of trials investigating WBAs on aBMD. The results of this meta-analysis conclude that WBAs alongside high calcium intake provide a practical, relevant method to significantly improve BMC in prepubertal children, justifying the application of this exercise form as an osteoporosis prophylaxis in this stage of maturity.

Can physical activity improve peak bone mass?

The pediatric origin of osteoporosis has led many investigators to focus on determining factors that influence bone gain during growth and methods for optimizing this gain. Bone responds to bone loading activities by increasing mass or size. Overall, pediatric studies have found a positive effect of bone loading on bone size and accrual, but the types of loads necessary for a bone response have only recently been investigated in human studies. Findings indicate that responses vary by sex, maturational status, and are site-specific. Estrogen status, body composition, and nutritional status also may influence the bone response to loading. Despite the complex interrelationships among these various factors, it is prudent to conclude that increased physical activity throughout life is likely to optimize bone health.

The impact on children's bone health of a school-based physical education program and participation in leisure time sports: the Childhood Health, Activity and Motor Performance School (the CHAMPS) study, Denmark

OBJECTIVE

To evaluate the effect of a school based physical education (PE) program and the amount of leisure time sport (LTS) on children's bone health and to examine if LTS influences the impact of school type on children's bone health.

METHODS

Children attending "sports" schools (6 × 45 min PE lessons per week) were compared to children at "traditional" schools (2 × 45 min of PE lessons per week) in Svendborg, Denmark. Whole-body DXA scans were performed at baseline (2008) and at a two-year follow-up (2010). Bone mineral content (BMC), bone mineral density (BMD), and bone area (BA) were measured. Multilevel regression analyses examined the impact of school type and LTS participation on bone.

RESULTS

742/800 (93%) invited children accepted to participate. 682/742 (92%) participated at two-year follow-up. Mean (SD) age was 9.5 years (0.9) at baseline. A positive association between LTS and BMC, BMD (p<0.001) and for BA (p<0.05) (total body less head (TBLH) and lower limb (LL)) was found. All effects regarding school type were insignificant.

CONCLUSION

A positive impact of attending LTS on bone traits was found. There was no effect on BMC, BMD and BA (TBLH, and LL) for children attending sports schools compared to traditional schools.

School-based physical activity programs for promoting physical activity and fitness in children and adolescents aged 6 to 18

BACKGROUND

The World Health Organization (WHO) estimates that 1.9 million deaths worldwide are attributable to physical inactivity and at least 2.6 million deaths are a result of being overweight or obese. In addition, WHO estimates that physical inactivity causes 10% to 16% of cases each of breast cancer, colon, and rectal cancers as well as type 2 diabetes, and 22% of coronary heart disease and the burden of these and other chronic diseases has rapidly increased in recent decades.

OBJECTIVES

The purpose of this systematic review was to summarize the evidence of the effectiveness of school-based interventions in promoting physical activity and fitness in children and adolescents.

SEARCH METHODS

The search strategy included searching several databases to October 2011. In addition, reference lists of included articles and background papers were reviewed for potentially relevant studies, as well as references from relevant Cochrane reviews. Primary authors of included studies were contacted as needed for additional information.

SELECTION CRITERIA

To be included, the intervention had to be relevant to public health practice (focused on health promotion activities), not conducted by physicians, implemented, facilitated, or promoted by staff in local public health units, implemented in a school setting and aimed at increasing physical activity, included all school-attending children, and be implemented for a minimum of 12 weeks. In addition, the review was limited to randomized controlled trials and those that reported on outcomes for children and adolescents (aged 6 to 18 years). Primary outcomes included: rates of moderate to vigorous physical activity during the school day, time engaged in moderate to vigorous physical activity during the school day, and time spent watching television. Secondary outcomes related to physical health status measures including: systolic and diastolic blood pressure, blood cholesterol, body mass index (BMI), maximal oxygen uptake (VO2max), and pulse rate.

DATA COLLECTION AND ANALYSIS

Standardized tools were used by two independent reviewers to assess each study for relevance and for data extraction. In addition, each study was assessed for risk of bias as specified in the Cochrane Handbook for Systematic Reviews of Interventions. Where discrepancies existed, discussion occurred until consensus was reached. The results were summarized narratively due to wide variations in the populations, interventions evaluated, and outcomes measured.

MAIN RESULTS

In the original review, 13,841 records were identified and screened, 302 studies were assessed for eligibility, and 26 studies were included in the review. There was some evidence that school-based physical activity interventions had a positive impact on four of the nine outcome measures. Specifically positive effects were observed for duration of physical activity, television viewing, VO2 max, and blood cholesterol. Generally, school-based interventions had little effect on physical activity rates, systolic and diastolic blood pressure, BMI, and pulse rate. At a minimum, a combination of printed educational materials and changes to the school curriculum that promote physical activity resulted in positive effects.In this update, given the addition of three new inclusion criteria (randomized design, all school-attending children invited to participate, minimum 12-week intervention) 12 of the original 26 studies were excluded. In addition, studies published between July 2007 and October 2011 evaluating the effectiveness of school-based physical interventions were identified and if relevant included. In total an additional 2378 titles were screened of which 285 unique studies were deemed potentially relevant. Of those 30 met all relevance criteria and have been included in this update. This update includes 44 studies and represents complete data for 36,593 study participants. Duration of interventions ranged from 12 weeks to six years.Generally, the majority of studies included in this update, despite being randomized controlled trials, are, at a minimum, at moderate risk of bias. The results therefore must be interpreted with caution. Few changes in outcomes were observed in this update with the exception of blood cholesterol and physical activity rates. For example blood cholesterol was no longer positively impacted upon by school-based physical activity interventions. However, there was some evidence to suggest that school-based physical activity interventions led to an improvement in the proportion of children who engaged in moderate to vigorous physical activity during school hours (odds ratio (OR) 2.74, 95% confidence interval (CI), 2.01 to 3.75). Improvements in physical activity rates were not observed in the original review. Children and adolescents exposed to the intervention also spent more time engaged in moderate to vigorous physical activity (with results across studies ranging from five to 45 min more), spent less time watching television (results range from five to 60 min less per day), and had improved VO2max (results across studies ranged from 1.6 to 3.7 mL/kg per min). However, the overall conclusions of this update do not differ significantly from those reported in the original review.

AUTHORS' CONCLUSIONS

The evidence suggests the ongoing implementation of school-based physical activity interventions at this time, given the positive effects on behavior and one physical health status measure. However, given these studies are at a minimum of moderate risk of bias, and the magnitude of effect is generally small, these results should be interpreted cautiously. Additional research on the long-term impact of these interventions is needed.

Habitual levels of high, but not moderate or low, impact activity are positively related to hip BMD and geometry: results from a population-based study of adolescents

Whether a certain level of impact needs to be exceeded for physical activity (PA) to benefit bone accrual is currently unclear. To examine this question, we performed a cross-sectional analysis between PA and hip BMD in 724 adolescents (292 boys, mean 17.7 years) from the Avon Longitudinal Study of Parents and Children (ALSPAC), partitioning outputs from a Newtest accelerometer into six different impact bands. Counts within 2.1 to 3.1g, 3.1 to 4.2g, 4.2 to 5.1g, and >5.1g bands were positively related to femoral neck (FN) BMD, in boys and girls combined, in our minimally adjusted model including age, height, and sex (0.5-1.1g: beta = -0.007, p = 0.8; 1.1-2.1g: beta = 0.003, p = 0.9; 2.1-3.1g: beta = 0.042, p = 0.08; 3.1-4.2g: beta = 0.058, p = 0.009; 4.2-5.1g: beta = 0.070, p = 0.001; >5.1g: beta = 0.080, p < 0.001) (beta = SD change per doubling in activity). Similar positive relationships were observed between high-impact bands and BMD at other hip sites (ward's triangle, total hip), hip structure indices derived by hip structural analysis of dual-energy X-ray absorptiometry (DXA) scans (FN width, cross-sectional area, cortical thickness), and predicted strength (cross-sectional moment of inertia). In analyses where adjacent bands were combined and then adjusted for other impacts, high impacts (>4.2g) were positively related to FN BMD, whereas, if anything, moderate (2.1-4.2g) and low impacts (0.5-2.1g) were inversely related (low: beta = -0.052, p = 0.2; medium: beta = -0.058, p = 0.2; high: beta = 0.137, p < 0.001). Though slightly attenuated, the positive association between PA and FN BMD, confined to high impacts, was still observed after adjustment for fat mass, lean mass, and socioeconomic position (high: beta = 0.096, p = 0.016). These results suggest that PA associated with impacts >4.2g, such as jumping and running (which further studies suggested requires speeds >10 km/h) is positively related to hip BMD and structure in adolescents, whereas moderate impact activity (eg, jogging) is of little benefit. Hence, PA may only strengthen lower limb bones in adolescents, and possibly adults, if this comprises high-impact activity.

Recovery of physical activity levels in adolescents after lower limb fractures: a longitudinal, accelerometry-based activity monitor study

Background

In adolescents, loss of bone mineral mass usually occurs during phases of reduced physical activity (PA), such as when an injured extremity spends several weeks in a cast. We recorded the PA of adolescents with lower limb fractures during the cast immobilization, at 6 and at 18 months after the fracture, and we compared these values with those of healthy controls.

Methods

Fifty adolescents with a first episode of limb fracture and a control group of 50 healthy cases were recruited for the study through an advertisement placed at the University Children’s Hospital of Geneva, Switzerland. PA was assessed during cast immobilization and at 6- and 18-month follow-up by accelerometer measurement (Actigraph® 7164, MTI, Fort Walton Beach, FL, USA). Patients and their healthy peers were matched for gender and age. Time spent in PA at each level of intensity was determined for each participant and expressed in minutes and as a percentage of total valid time.

Results

From the 50 initial teenagers with fractures, 44 sustained functional evaluations at 6 months follow-up, whereas only 38 patients were studied at 18 months. The total PA count (total number of counts/min) was lower in patients with lower limb fractures (-62.4%) compared with healthy controls (p<0.0001) during cast immobilization. Similarly, time spent in moderate-to-vigorous PA was lower by 76.6% (p<0.0001), and vigorous PA was reduced by 84.4% (p<0.0001) in patients with cast immobilization for lower limb injuries compared to healthy controls values. At 6 and 18 months after the fracture, the mean PA level of injured adolescents was comparable to those of healthy teenagers (-2.3%, and -1.8%, respectively).

Importantly, we observed that time spent in vigorous PA, which reflects high-intensity forces beneficial to skeletal health, returned to similar values between both groups from the six month follow-up in adolescents who sustained a fracture. However, a definitive reduction in time spent in moderate PA was observed among patients with a lower limb fracture at 18 months, when comparing with healthy controls values (p = 0.0174).

Conclusions

As cast immobilization and reduced PA are known to induce bone mineral loss, this study provides important information to quantify the decrease of skeletal loading in adolescents with limb fractures. The results of this study demonstrate that the amount of skeletal loading returns to normal values in adolescents with lower limb fractures after bone healing and is probably linked to an overall better pattern of functional recovery among this age group. When comparing both populations of adolescents, a definitive decrease in time spent in moderate-to-vigorous PA was observed among patients with a lower limb fracture at 18 months and may suggest a modification of lifestyle. The high rate of missing data (26.5%) due to above all non compliance with monitor wearing among teenagers complicates the data analysis, and requires a more cautious interpretation of the results. Future studies using accelerometer to monitor PA in adolescents should therefore include strategies for improving the rate of adherence and minimizing the ratio of missing data.

Bone mineral density changes after physical training and calcium intake in students with attention deficit and hyper activity disorders

In this study we investigate the effects of weight bearing exercise and calcium intake on bone mineral density (BMD) of students with attention deficit and hyper activity (ADHD) disorder. For this reason 54 male students with ADHD (age 8-12 years old) were assigned to four groups with no differences in age, BMD, calcium intake, and physical activity: exercise groups with or without calcium supplementation (Ex+Ca+ and Ex+Ca-) and non-exercise groups with or without calcium supplementation (Ex-Ca+ and Ex-Ca-). The intervention involved 50 min of weight bearing exercise performed 3 sessions a week and/or the addition of dietary calcium rich food using enriched cow milk with vitamin D containing 250 mg calcium per serving, over 9 months. Paired-samples t-test, one way ANOVA analysis, and Tukey tests were used to determine the main and combined effects of training and calcium on BMD. All groups showed greater femoral neck BMD after 9 months. The increase in femoral neck BMD was significantly different between all groups (p < 0.05). Ex+Ca+ group has greater increase in BMD than other groups. Apparently, the effect of training was greater than calcium intake (p < 0.05). These results help to provide more evidence for public health organizations to deal with both exercise and nutrition issues in children with ADHD disorder for the achievement of peak BMD.

Physical activity in childhood may be the key to optimizing lifespan skeletal health

Physical activities undertaken in childhood, particularly activities, which apply large forces quickly convey optimal benefits to bone mass, size, and structure. Evidence is accumulating that benefits persist well beyond activity cessation. This review examines the potential for early childhood activity to improve bone mineralization and structure and explores childhood activity as prevention for osteoporosis in later life.

Decrease of physical activity level in adolescents with limb fractures: an accelerometry-based activity monitor study

Background

Immobilization and associated periods of inactivity can cause osteopenia, the physiological response of the bone to disuse. Mechanical loading plays an essential role in maintaining bone integrity. Skeletal fractures represent one cause of reduction of the physical activity (PA) level in adolescents. The purpose of this study was to quantify the reduction of PA in adolescents with limb fractures during the cast immobilization period compared with healthy controls.

Methods

Two hundred twenty adolescents were divided into three groups: those with upper limb fractures (50 cases); lower limb fractures (50 cases); and healthy cases (120 cases). Patients and their healthy peers were matched for gender, age, and seasonal assessment of PA. PA level was assessed during cast immobilization by accelerometer. Time spent in PA in each of the different intensity levels - sedentary, light, moderate, and vigorous - was determined for each participant and expressed in minutes and as a percentage of total valid time.

Results

Reduction in PA during cast immobilization was statistically significant in patients with limb fractures compared to healthy controls. The total PA count (total number of counts/min) was significantly lower in those with upper and lower limb fractures (-30.1% and -62.4%, respectively) compared with healthy controls (p < 0.0001 and p = 0.0003, respectively). Time spent in moderate-to-vigorous PA by patients with upper and lower limb injuries decreased by 36.9% (p = 0.0003) and 76.6% (p < 0.0001), respectively, and vigorous PA was reduced by 41.4% (p = 0.0008) and 84.4% (p < 0.0001), respectively.

Conclusions

PA measured by accelerometer is a useful and valid tool to assess the decrease of PA level in adolescents with limb fractures. As cast immobilization and reduced PA are known to induce bone mineral loss, this study provides important information to quantify the decrease of skeletal loading in this patient population. The observed reduction of high intensity skeletal loading due to the decrease in vigorous PA may explain osteopenia due to disuse, and these data should be kept in mind by trauma practitioners to avoid any unnecessary prolongation of the cast immobilization period.

Effect of a general school-based physical activity intervention on bone mineral content and density: a cluster-randomized controlled trial

BACKGROUND

Specific physical loading leads to enhanced bone development during childhood. A general physical activity program mimicking a real-life situation was successful at increasing general physical health in children. Yet, it is not clear whether it can equally increase bone mineral mass. We performed a cluster-randomized controlled trial in children of both gender and different pubertal stages to determine whether a school-based physical activity (PA) program during one school-year influences bone mineral content (BMC) and density (BMD), irrespective of gender.

METHODS

Twenty-eight 1st and 5th grade (6-7 and 11-12 year-old) classes were cluster randomized to an intervention (INT, 16 classes, n=297) and control (CON; 12 classes, n=205) group. The intervention consisted of a multi-component PA intervention including daily physical education with at least 10 min of jumping or strength training exercises of various intensities. Measurements included anthropometry, and BMC and BMD of total body, femoral neck, total hip and lumbar spine using dual-energy X-ray absorptiometry (DXA). PA was assessed by accelerometers and Tanner stages by questionnaires. Analyses were performed by a regression model adjusted for gender, baseline height and weight, baseline PA, post-intervention pubertal stage, baseline BMC, and cluster.

RESULTS

275 (72%) of 380 children who initially agreed to have DXA measurements had also post-intervention DXA and PA data. Mean age of prepubertal and pubertal children at baseline was 8.7±2.1 and 11.1±0.6 years, respectively. Compared to CON, children in INT showed statistically significant increases in BMC of total body, femoral neck, and lumbar spine by 5.5%, 5.4% and 4.7% (all p<0.05), respectively, and BMD of total body and lumbar spine by 8.4% and 7.3% (both p<0.01), respectively. There was no gender *group, but a pubertal stage *group interaction consistently favoring prepubertal children.

CONCLUSION

A general school-based PA intervention can increase bone health in elementary school children of both genders, particularly before puberty.

Physical activity positively predicts bone architecture and bone strength in adolescent males and females

AIMS

Physical activity (PA) has positive effects on bone accrual and geometry in children during growth. However, we do not know how PA influences adaptations in bone architecture during growth. We evaluated the contribution of PA to bone density, architecture and strength in adolescents.

METHODS

We used HR-pQCT (XtremeCT, Scanco Medical) to assess cross-sectional moments of inertia [Imin, Imax (mm⁴)], total bone density (Tt.Dn, mg HA/cm³), total bone area (Tt.Ar, mm²), cortical bone density (Ct.Dn, mg HA/cm³), cortical thickness (Ct.Th, μm), trabecular bone density (Tb.Dn, mg HA/cm³), trabecular number (Tb.N, mm⁻¹) and trabecular thickness (Tb.Th, μm) at the distal tibia in 146 male and 132 female participants (15-20 years). We evaluated the contribution of impact loading PA (ImpactPA) and non-impact loading PA (NoimpactPA) on bone (p < 0.05).

RESULTS

ImpactPA explained 10% of variance in Imin (p = 0.000), and 12% of variance in Imax (p = 0.000) in male participants. In male participants, ImpactPA explained 6% of variance in Tt.Ar (p = 0.003). In female participants, ImpactPA explained 4% of variance in Tt.Dn (p = 0.011), 5% of variance in Tb.Dn (p = 0.004) and 8% of variance in Tb.N (p = 0.001).

CONCLUSION

Our findings suggest that ImpactPA is significantly associated with bone architecture and bone strength in adolescent males and females.

Integration of short bouts of physical activity into organizational routine a systematic review of the literature

CONTEXT

Recommended daily physical activity accumulated in short intervals (e.g., <10 minutes) may be more feasible and appealing to the relatively sedentary populace than longer bouts. The purpose of this paper is to present a systematic review of the evidence for the effectiveness of short activity bouts incorporated into organizational routine as part of the regular "conduct of business."

EVIDENCE ACQUISITION

PubMed, MEDLINE, and Google Scholar databases were searched in August 2009 (updated search in February and July 2010) to identify relevant, peer-reviewed journal articles and abstracts on school-, worksite-, and faith-based interventions of short, structurally integrated physical activity breaks.

EVIDENCE SYNTHESIS

The majority of interventions implemented daily physical activity bouts of 10-15 minutes in length. Schools were the most common settings among the 40 published articles included in this review. The rigor of the studies varied by setting, with more than 75% of worksite versus 25% of school studies utilizing RCT designs. Studies focused on a broad range of outcomes, including academic/work performance indicators, mental health outcomes, and clinical disease risk indicators, in addition to physical activity level. Physical activity was the most commonly assessed outcome in school-based studies, with more than half of studies assessing and observing improvements in physical activity outcomes following the intervention. About a quarter of worksite-based studies assessed physical activity, and the majority found a positive effect of the intervention on physical activity levels. About half of studies also observed improvements in other relevant outcomes such as academic and work performance indicators (e.g., academic achievement, cognitive performance, work productivity); psychosocial factors (e.g., stress, mood); and clinical disease risk indicators (e.g., blood pressure, BMI). The average study duration was more than 1 year, and several reported outcomes at 3-6 years.

CONCLUSIONS

Interventions integrating physical activity into organizational routine during everyday life have demonstrated modest but consistent benefits, particularly for physical activity, and these are promising avenues of investigation. The proportionately longer-term outcomes available in these studies compared with individual-level studies suggest that physical activity promotion strategies at the organizational level may be more sustainable.