Bone mass and structure are enhanced following a 2-year randomized controlled trial of exercise in prepubertal boys

Skeletal Loading: Lean and Bone Mass Development in Young Elite Male Gymnasts, Swimmers, and Nonathletes Aged 6-24 Years

BACKGROUND

Exercise optimizes peak bone mass accrual, particularly if the loading is high magnitude and distributed in abnormal directions. Little is known about the influence of early intense training in sport during peak bone mass accrual, especially in boys.

METHODS

Ninety-eight males aged 6-24 years (gymnasts, swimmers, and controls) completed the bone-specific physical activity questionnaire and a 7-day exercise diary. Dual-energy X-ray absorptiometry determined bone mineral properties of the total body (less head) and lumbar spine (LS, L1-L4) and total lean mass. Subgroup analyses were conducted for juniors (prepubescent), adolescents (11-16 y), and seniors (17-24 y).

RESULTS

Lean mass was positively associated with total body less head and LS bone outcomes in all 3 age groups (R2 = .632-.770, P < .05), and bone-specific physical activity questionnaire scores were associated with LS bone mineral density in adolescents and seniors (R2 = .440 and .591, P < .05). Senior gymnasts had significantly higher LS bone mineral density (in grams per square centimeter) and Z-scores than swimmers (P = .004) and controls (P = .012).

CONCLUSIONS

Elite gymnastics is associated with superior peak bone mass accrual in young males. The benefits appear more pronounced during young adulthood compared with prepuberty, potentially reflecting an extended time course for bone adaptation.

An 8-Week Virtual Exercise Training Program for Pediatric Solid Organ Transplant Recipients

PURPOSE

Musculoskeletal strength can be impaired in pediatric solid organ transplant recipients. Exercise training programs can be beneficial but in-person delivery can be challenging; virtual exercise programs can alleviate some of these challenges. This feasibility study aimed to deliver an 8-week virtual exercise program in pediatric solid organ transplant recipients.

METHOD

Program delivery occurred 3 times per week for 30 minutes. An exercise stress test was completed prior to program start. The Bruininks-Oseretsky Test of Motor Proficiency strength subtest and self-report surveys were used to assess musculoskeletal strength, quality of life, fatigue, and physical activity. Contact was maintained through a text messaging platform. Z scores were calculated using standardized normative data. Medians (interquartile range) are reported for all other data.

RESULTS

Eleven participants completed the program (2 liver, 5 kidney, 4 heart; 58% females; median age = 11.5 [10.3-13.8] y). Six participants attended ≥60% of classes, 5 participants attended <50% of classes. After 8 weeks, strength scores improved (Z score, Pre: -1.0 [-1.65 to -0.60] to Post: -0.2 [-1.30 to 0.40]; P = .007) with no change in other outcome measures.

CONCLUSION

The virtual exercise program was delivered without technical issues and received positive participant feedback. Engagement and costs need to be considered.

Low bone mineral density is associated with fatty liver disease and respiratory illness in a pediatric mortality sample

This study finds that fatty liver disease is associated with low bone density in a pediatric mortality sample. Since non-alcoholic fatty liver disease has increased in prevalence over the past few decades among children, a better understanding of the disease's impacts on bone health is of significance to clinicians.

PURPOSE

Chronic illness leads to decreased bone modeling and remodeling. This can be especially problematic during childhood and adolescence, since the majority of an individual's peak bone mass is achieved by the age of 20. In this study, we examine relationships between chronic illness and low bone mineral density (BMD) in a pediatric mortality sample (aged 0.5 to 20.9 years) from New Mexico. We also test whether low BMD is related to decelerated linear growth by examining its relationship to growth stunting and arrest (Harris lines).

METHODS

Hounsfield units (HU), a proxy for trabecular BMD, were obtained at the fourth lumbar vertebra and the femoral neck from postmortem CT scans. Linear regression was used to examine associations between z-standardized HU and age, sex, medical conditions, Harris lines, and growth stunting.

RESULTS

We find that lumbar HU is significantly lower for individuals with fatty liver disease and respiratory illness; femoral HU is significantly lower in individuals with Harris lines.

CONCLUSION

The mechanisms of low BMD in individuals with fatty liver disease and respiratory illness are likely multifactorial and involve vitamin D deficiency (malnutrition, malabsorption), systemic inflammation, and sedentary lifestyles. However, better awareness of this relationship can provide clinicians with the ability to introduce nutritional and behavioral interventions early to mitigate deleterious effects on bone. Harris lines, on the other hand, mark temporary growth cessation due to physiological stress followed by a rapid resumption of growth. Low BMD in these individuals may be due to bone mineralization lagging behind relatively rapid linear growth.

The Benefits to Bone Health in Children and Pre-School Children with Additional Exercise Interventions: A Systematic Review and Meta-Analysis

OBJECTIVE

Determine if exercise interventions, beyond what is already provided to children and preschool children, improve bone health and reduce fracture incidence.

DESIGN

Systematic review and meta-analysis reported using the PRISMA guidelines. Certainty of evidence was assessed using GRADE recommendations.

DATA SOURCES

Five electronic databases were searched for records: PUBMED; CINAHL; CENTRAL; SPORTDiscus; Web of Science.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Randomised, quasi-randomised and non-randomised controlled trials (including cluster-randomised) assessing the impact of additional exercise interventions (e.g., increased physical education classes or specific jumping programs) on bone health in children (6-12 years) and pre-school children (2-5 years) without dietary intervention.

RESULTS

Thirty-one records representing 16 distinct clinical trials were included. Dual-energy X-ray Absorptiometry (DXA) and/or peripheral Quantitative Computed Tomography (pQCT) were used to quantify bone health. Increased femoral neck bone mineral content in children with additional exercise interventions (n = 790, SMD = 0.55, 95% CI = 0.01 to 1.09) was reported, however this was not significant following sensitivity analysis. Other DXA and pQCT measures, as well as fracture incidence, did not appear to significantly differ over time between intervention and control groups. No studies reported adverse events. Studies failed to report all domains within the TIDieR checklist. All studies were at high risk of bias using the Cochrane RoB Tool 2.0. The certainty of the evidence was very low.

CONCLUSIONS

The addition of exercise interventions, beyond what is provided to children, does not appear to improve DXA and pQCT measures of bone health. The effect of additional exercise interventions on bone health in pre-school children is largely unknown. Future trials should ensure adherence is clearly reported and controlled for within analysis as well as including reports of adverse events (e.g., apophysitis) that occur due to increased exercise interventions.

Adiposity, Insulin Resistance, Cardiorespiratory Fitness, and Bone Health in Hispanic Children

CONTEXT

Childhood obesity disproportionately affects Hispanic youth. The skeletal system appears to be a target organ of the adverse effects of obesity. Yet, the relationship between adiposity and bone health in youth and the modulating factors are not well understood.

OBJECTIVE

This work aims to examine the relationship between adiposity, insulin resistance (IR), cardiorespiratory fitness (CRF), and bone mass in Hispanic youth.

METHODS

A total of 951 Hispanic youth (50% male), aged 4 to 19 years, participated in this cross-sectional design study from the Viva La Familia Study at Children's Nutrition Research Center. Bone mineral content (BMC) and density (BMD), lean mass (LM), total body fat mass (FM), truncal FM were obtained using dual-energy x-ray absorptiometry. Fasting glucose and insulin were obtained and the homeostasis model assessment of insulin resistance (HOMA-IR) was calculated. CRF was measured using a treadmill ramp protocol. We applied linear regression models and mediation analyses.

RESULTS

Adiposity measures were negatively related to BMC and BMD after accounting for LM and sex. IR negatively contributed whereas CRF positively contributed to the variance in BMC and BMD, more notably in the pubertal age group. In mediation analysis, HOMA-IR partially mediated the negative relationship of adiposity to BMC (standardized indirect effect [IE] = -0.0382; 95% CI, -0.0515 to -0.0264) whereas the sequential IE of HOMA-IR and CRF partially attenuated (IE = -0.0026; 95% CI, -0.0053 to -0.0005) this relationship. Similar findings were seen with BMD as the primary outcome.

CONCLUSION

IR mediates the negative relationship between adiposity and bone mass whereas CRF may partially attenuate it.

Physical Education and Sports: A Backbone of the Entire Community in the Twenty-First Century

The current state of physical inactivity of people can be traced back to the people who have been denied their fundamental human right to physical education and participation in school sports (PES). Growing up without the fundamental human right to free movement and participation in sports activities enabled students to stay physically inactive. The purpose of this study was to explore what is currently known about the role of PES in all areas of human development and SDGs and to raise awareness about PES, which has been shown to be on the decline. To increase the study’s overall efficacy, an external desk research approach was employed to gather relevant information published online: reports, policies, charters, recommendations, and other relevant articles from various electronic databases and websites of international organizations responsible for PES, culture, and health. PES benefits are discussed in all domains of human development, including physical and mental health, cognitive, psychosocial, and moral benefits. Contrary to its importance to human growth as a whole, PES has been sidelined since the end of the twentieth century. An awareness of the subject of PES has thus been raised as a backbone of the entire community in the twenty-first century, so as to translate the promises and policies of PES into realities and practices.

Is the Secret in the Gut? SuperJump Activity Improves Bone Remodeling and Glucose Homeostasis by GLP-1 and GIP Peptides in Eumenorrheic Women

We showed that twenty weeks of SuperJump activity, an innovative workout training performed on an elastic minitrampoline, reduced bone resorption and increased bone formation in eumenorrheic women acting on the key points of the regulation of bone metabolism. The present study analyzed whether the gastrointestinal hormones are involved in the mechanism of action and if it has an impact on glucose homeostasis. The control group was composed of twelve women, similar to the exercise group that performed SuperJump activity for twenty weeks. The analysis was performed on blood samples and investigated GLP-1, GIP, GLP-2, PYY, ghrelin, glucose, insulin, insulin resistance, β-cell function, and insulin sensitivity. The results showed that the activity contributes to raising the GLP-1and GIP levels, and not on GLP-2, PYY, and ghrelin, which did not change. Moreover, SuperJump activity significantly reduced fasting insulin, glucose, insulin resistance, and increased insulin sensitivity but did not affect beta cell function. These data suggest that GLP-1, and GIP are involved in the mechanism of action that improves bone and glucose homeostasis following 20 weeks of SuperJump activity in eumenorrheic women.

The Efficacy of Brief School-Based Exercise Programs in Improving Pubertal Bone Mass and Physical Fitness: A Randomized Controlled Trial

PURPOSE

To examine the effects of three types of school-based exercises on bone health and physical fitness function in Chinese boys and girls.

METHODS

One hundred and seventy-four Chinese boys and girls were randomly assigned into four groups: (1) sham exercise (ShEx); (2) high-impact exercise (HiEx); (3) high-impact exercise with various directions (HiExVi); and (4) high-intensity interval exercise (HiInEx). Speed of sound (SOS) and physical fitness parameters were determined before and after six-month intervention.

RESULTS

At the end of six-month intervention, participants in all groups show an increment of SOS compared with the baseline (p < 0.05), and the changes were higher in HiEx (mean: 38.878 m/s, 95% CI: 32.885~44.872, p = 0.001) and HiExVi groups (49.317 m/s, 42.737~55.897, p < 0.001) compared with ShEx group (20.049 m/s, 13.751~26.346). Six-month exercise training generated a reduction of percent of body fat (PBF) and waist-hip ratio (WHR) (p < 0.05). The decrease of PBF was greater in HiExVi (-1.222%, -1.820~-0.624, p = 0.012) and HiInEx groups (-1.395%, -1.809~-0.982, p = 0.003), whereas the reduction of WHR was larger in HiEx (-0.026, -0.039~-0.014, p = 0.009), HiExVi (-0.024, -0.036~-0.012, p = 0.021), and HiInEx groups (-0.035, -0.046~-0.024, p < 0.001) compared with ShEx group. Balance function (BLF), vital capacity (VC), standing long jump (SLJ), and sit up (SU) increased in all intervention groups (p < 0.05). The BLF increased in HiEx (6.332 s, 4.136~8.528, p = 0.001), HiExVi (10.489 s, 8.934~12.045, p < 0.001), and HiInEx groups (9.103 s, 7.430~10.776, p < 0.001) showed a greater change than that of ShEx group (1.727 s, 0.684~2.770). The increment of VC (273.049 mL, 199.510~346.587, p < 0.001) and SU (2.537 times/min, 0.639~4.435, p = 0.017) was higher in HiInEx group, whereas the accrual in SLJ was larger in HiExVi (7.488 cm, 4.936~10.040, p = 0.007) compared with ShEx group (58.902 mL, 7.990~109.814; -0.463 times/min, -2.003~1.077; 1.488 cm, -0.654~3.630).

CONCLUSION

The brief school-based exercises were effective in improving schoolchildren's health, but they showed different effects, with HiEx mostly improving bone health, HiInEx largely benefiting physical fitness function, and HiExVi enhancing both bone and physical fitness.

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.

Cystic fibrosis bone disease treatment: Current knowledge and future directions

Bone disease is a frequent complication in adolescents and adults with cystic fibrosis (CF). Early detection and monitoring of bone mineral density and multidisciplinary preventive care are necessary from childhood through adolescence to minimize CF-related bone disease (CFBD) in adult CF patients. Approaches to optimizing bone health include ensuring adequate nutrition, particularly intake of calcium and vitamins D and K, addressing other secondary causes of low bone density such as hypogonadism, encouraging weight bearing exercise, and avoiding bone toxic medications. Of the currently available anti-resorptive or anabolic osteoporosis medications, only bisphosphonates have been studied in individuals with CF. Future studies are needed to better understand the optimal approach for managing CFBD.

Prevention of osteoporosis in cystic fibrosis

PURPOSE OF REVIEW

The increased life span of patients with cystic fibrosis has lead to the detection of new complications. Osteopenia is present in up to 50% of adult patients with cystic fibrosis, and osteoporosis in 10-34% and can cause a difficult management problem.

RECENT FINDINGS

In children, defects in bone health become apparent generally at adolescence because of suboptimall bone peak mass achievement. Malnutrition, inflammation, vitamin D and vitamin K deficiency, altered sex hormone production, glucocorticoid therapy, and physical inactivity potentiate poor bone health.

SUMMARY

Monitoring bone mineral density and preventive care of osteoporosis are necessary from childhood to minimize cystic fibrosis-related bone disease in adult cystic fibrosis patients.

Bone Health and Its Relationship with Impact Loading and the Continuity of Physical Activity throughout School Periods

Bone is influenced by physical activity (PA) throughout life, but childhood and adolescence provide a key opportunity to maximize peak bone mass. Thus, it is important to identify the relationship between PA practiced in childhood and young adulthood to design a promotion plan for bone health. The purpose of this study was to analyze the relationship between different impact-loading PAs (and their continuity throughout school periods from childhood to young adulthood) and bone stiffness index (SI). In this cross-sectional study, which was conducted on 145 university students aged 18-21 years, bone measurements were measured by quantitative ultrasonometry (QUS), and PA information was recalled using a self-administered questionnaire. Associations between the SI and the impact of PA performed during secondary school (p = 0.027), high school (p = 0.002), and university (p = 0.016) periods were observed. The continuity of PA over a longer period of time was related to a higher SI (p = 0.007). Those who practiced PA throughout all school periods had a higher SI than those who practiced during primary school only (p = 0.038) or through primary and secondary schools (p = 0.009). These results suggest that impact-loading PA practiced during different school periods is related to higher values of the SI. Therefore, continuous PA from an early age may be an important contributing factor to achieving and maintaining adequate bone health.

Effect of assisted walking-movement in patients with genetic and acquired neuromuscular disorders with the motorised Innowalk device: an international case study meta-analysis

People with physical disabilities (PD) suffer from consequences due to lack of physical activity and consequently, are at increased risk of chronic diseases. We aimed to evaluate the ability of a motorised assistive device for dynamic standing with weight-bearing in addition to standard state-of-the-art therapy to improve clinical outcome in a meta-analysis of available studies. A total of 11 studies were identified from different European countries analysing the effect of the dynamic device Innowalk. Raw data of nine studies were pooled including a total of 31 patients observed between 2009 and 2017. Standardised questionnaires and physical outcomes were examined in this exploratory meta-analysis. We recorded patients' characteristics, duration, intensity, and location of usage as well as general clinical outcomes and improvement of passive range of motion (PROM). The analysed population consisted in 90% cases of patients younger than 18 years of age. Patients were severely disabled individuals (aged 8 (6-10) years; 58% male; 67% non-ambulatory, 86% cerebral palsy). A total of 94% used the Innowalk in a home-based or day-care setting. For nearly all individuals (94%), improvements were recorded for: walking or weight-bearing transfer (n = 13), control/strength of the trunk or head (n = 6), joint mobility (n = 14), sleep (n = 4 out of 6/67%), or muscle strength (n = 17), vital functions (n = 16), bowel function (n = 10), attention/orientation (n = 2). PROM of the hip (flexion, abduction, and adduction) significantly (p < 0.001 for multiple comparisons) increased after 1 month (p < 0.05 flexion, adduction) and further after 5 months (p < 0.05 each) in contrast (p < 0.05 each) to a control group with state-of-the-art therapy. Similarly, PROM showed a trend towards improvement in dorsal extension of the ankle (p = 0.07). In summary, this is the first report of a novel device with additional benefit to standard therapy for severe PD. These intriguing results warrant the planned prospective randomised controlled trial to prove the concept and mechanism of action of this device.

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.

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

BACKGROUND

Arthritis in childhood can be associated with muscle weakness around affected joints, low bone mass and low bone strength. Exercise is recognized as an important part of management of children with juvenile idiopathic arthritis (JIA) but the exercise prescription to best promote bone and muscle health is unknown. We therefore aimed to: 1. assess feasibility and safety of a 6-month home- and group-based exercise program for children with JIA; 2. estimate the effect of program participation on bone mass and strength, muscle function and clinical outcomes and 3. determine if any positive changes in bone and muscle outcomes are maintained 6 months later.

METHODS

We recruited 24 children with JIA who were part of the Linking Exercise, Physical Activity and Pathophysiology in Childhood Arthritis (LEAP) study to participate in a 6-month home-based exercise program involving jumping and handgrip exercises, resistance training and one group exercise session per month. We assessed lumbar spine bone mass (dual energy X-ray absorptiometry), distal tibia and radius bone microarchitecture and strength (high-resolution peripheral quantitative computed tomography), muscle function (jumping mechanography, dynamometry) and clinical outcomes (joint assessment, function, health-related quality of life) at baseline, 6- and 12-months. Adherence was assessed using weekly activity logs.

RESULTS

Thirteen children completed the 6-month intervention. Participants reported 9 adverse events and post-exercise pain was rare (0.4%). Fatigue improved, but there were no other sustained improvements in muscle, bone or clinical outcomes. Adherence to the exercise program was low (47%) and decreased over time.

CONCLUSION

Children with JIA safely participated in a home-based exercise program designed to enhance muscle and bone strength. Fatigue improved, which may in turn facilitate physical activity participation. Prescribed exercise posed adherence challenges and efforts are needed to address facilitators and barriers to participation in and adherence to exercise programs among children with JIA.

TRIAL REGISTRATION

Data of the children with JIA are from the LEAP study (Canadian Institutes of Health Research (CIHR; GRANT# 107535 ). http://www.leapjia.com/.

Diet and Exercise: a Match Made in Bone

PURPOSE OF REVIEW

Multiple dietary components have the potential to positively affect bone mineral density in early life and reduce loss of bone mass with aging. In addition, regular weight-bearing physical activity has a strong positive effect on bone through activation of osteocyte signaling. We will explore possible synergistic effects of dietary components and mechanical stimuli for bone health by identifying dietary components that have the potential to alter the response of osteocytes to mechanical loading.

RECENT FINDINGS

Several (sub)cellular aspects of osteocytes determine their signaling towards osteoblasts and osteoclasts in response to mechanical stimuli, such as the osteocyte cytoskeleton, estrogen receptor α, the vitamin D receptor, and the architecture of the lacunocanalicular system. Potential modulators of these features include 1,25-dihydroxy vitamin D3, several forms of vitamin K, and the phytoestrogen genistein. Multiple dietary components potentially affect osteocyte function and therefore may have a synergistic effect on bone health when combined with a regime of physical activity.

One-Year Follow-up of the CAPO Kids Trial: Are Physical Benefits Maintained?

PURPOSE

To determine the 12-month maintenance of a 9-month, thrice-weekly, 10-minute high-intensity exercise program, delivered in schools, on bone and other health-related performance variables in prepubertal children.

METHODS

All participants (N = 311) of the CAPO kids trial (testing times T1-T2) were contacted to undergo retesting (T3) of all original measures-including weight, standing and sitting height, calcaneal broadband ultrasound attenuation (Achilles, GE), and stiffness index (Achilles, GE)-waist circumference, resting heart rate, blood pressure, vertical jump, and aerobic capacity. Maturity was determined by estimating age of peak height velocity using sex-specific regression equations.

RESULTS

A total of 240 children [12.3 (0.6) y old] were included in the current study (77% of initial follow-up sample at T2). Between the T2 and T3 time points, both exercise (EX) group and control (CON) group increased broadband ultrasound attenuation (EX: 5.6%, P ≤ .001; CON: 6.5%, P ≤ .001), stiffness index (EX: 7.3%, P ≤ .001; CON: 5.2%, P ≤ .001), vertical jump (EX: 5.9%, P ≤ .001; CON: 6.3%, P ≤ .001), estimated maximal oxygen consumption (EX: 13.3%, P ≤ .001; CON: 12.1%, P ≤ .001), and reduced waist circumference (EX: -5.2%, P ≤ .001; CON: -5.6%, P ≤ .001), with no between-group differences in the magnitude of those changes. No differences were detected in absolute values between groups at T3.

CONCLUSION

Although the statistically significant differences observed between groups following the intervention were no longer significant 1 year after withdrawal of the intervention, the between-group similarities in growth trajectories of those parameters could suggest that some benefit of the intervention for bone health, waist circumference, and physical performance endured.

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.

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.

Fitness Effects of 10-Month Frequent Low-Volume Ball Game Training or Interval Running for 8-10-Year-Old School Children

We investigated the exercise intensity and fitness effects of frequent school-based low-volume high-intensity training for 10 months in 8–10-year-old children. 239 Danish 3rd-grade school children from four schools were cluster-randomised into a control group (CON, n = 116) or two training groups performing either 5 × 12 min/wk small-sided football plus other ball games (SSG, n = 62) or interval running (IR, n = 61). Whole-body DXA scans, flamingo balance, standing long-jump, 20 m sprint, and Yo-Yo IR1 children's tests (YYIR1C) were performed before and after the intervention. Mean running velocity was higher (p < 0.05) in SSG than in IR (0.88 ± 0.14 versus 0.63 ± 0.20 m/s), while more time (p < 0.05) was spent in the highest player load zone (>2; 5.6 ± 3.4 versus 3.7 ± 3.4%) and highest HR zone (>90% HR_max; 12.4 ± 8.9 versus 8.4 ± 8.0%) in IR compared to SSG. After 10 months, no significant between-group differences were observed for YYIR1C performance and HR after 2 min of YYIR1C (HR_submax), but median-split analyses showed that HR_submax was reduced (p < 0.05) in both training groups compared to CON for those with the lowest aerobic fitness (SSG versus CON: 3.2%  HR_max [95% CI: 0.8–5.5]; IR versus CON: 2.6%  HR_max [95% CI: 1.1–5.2]). After 10 months, IR had improved (p < 0.05) 20 m sprint performance (IR versus CON: 154 ms [95% CI: 61–241]). No between-group differences (p > 0.05) were observed for whole-body or leg aBMD, lean mass, postural balance, or jump length. In conclusion, frequent low-volume ball games and interval running can be conducted over a full school year with high intensity rate but has limited positive fitness effects in 8–10-year-old children.

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.

Volleyball and Basketball Enhanced Bone Mass in Prepubescent Boys

The aim of this study was to examine the effect of volleyball and basketball practice on bone acquisition and to determine which of these 2 high-impact sports is more osteogenic in prepubertal period. We investigated 170 boys (aged 10-12 yr, Tanner stage I): 50 volleyball players (VB), 50 basketball players (BB), and 70 controls. Bone mineral content (BMC, g) and bone area (BA, cm(2)) were measured by dual-energy X-ray absorptiometry at different sites. We found that, both VB and BB have a higher BMC at whole body and most weight-bearing and nonweight-bearing sites than controls, except the BMC in head which was lower in VB and BB than controls. Moreover, only VB exhibited greater BMC in right and left ultra-distal radius than controls. No significant differences were observed between the 3 groups in lumbar spine, femoral neck, and left third D radius BMC. Athletes also exhibited a higher BA in whole body, limbs, lumbar spine, and femoral region than controls. In addition, they have a similar BA in head and left third D radius with controls. The VB exhibited a greater BA in most radius region than controls and a greater femoral neck BA than BB. A significant positive correlation was reported between total lean mass and both BMC and BA in whole body, lumbar spine, total hip, and right whole radius among VB and BB. In summary, we suggest that volleyball and basketball have an osteogenic effect BMC and BA in loaded sites in prepubescent boys. The increased bone mass induced by both volleyball and basketball training in the stressed sites was associated to a decreased skull BMC. Moreover, volleyball practice produces a more sensitive mechanical stress in loaded bones than basketball. This effect seems translated by femoral neck expansion.

Persistent Effect of Vitamin D Supplementation on Musculoskeletal Parameters in Adolescents One Year After Trial Completion

We showed a beneficial effect of vitamin D supplementation on musculoskeletal parameters in adolescent girls in a 1-year, randomized, double-blinded placebo-controlled trial (RCT). Our objective for this study was to investigate the residual effect of vitamin D supplementation on bone mineral content (BMC), bone mineral density (BMD), at the lumbar spine and hip, lean mass, and height, 1 year after trial completion. We performed post hoc analyses in 167 adolescents, 86 girls and 81 boys, age 13.9 ± 2 years, who received vitamin D or placebo during the trial, and continued into the follow-up trial. Musculoskeletal parameters were measured at baseline, 12 months (intervention), and 24 months (follow-up). ANOVA and t tests were used to compare results between the placebo group and the merged vitamin D arms (200 or 2000 IU/day), by gender. Baseline characteristics were comparable between treatment groups at entry into the extension. Girls who had received vitamin D during the trial, had significantly larger hip BMC increments compared to those assigned to placebo, at 24 months compared to study entry, but not 24 compared to 12 months, which persisted in adjusted analyses. There were no significant differences in bone mass changes between treatment groups in boys, at 24 months compared to 12 months or to baseline. The beneficial effect of vitamin D supplementation on hip bone mass, achieved in girls during the trial, persisted 1 year after trial completion. These net cumulative increments, 1 year after discontinuation of supplementation, may have important implications on optimizing peak bone mass accretion in adolescent girls. © 2016 American Society for Bone and Mineral Research.

State of the Art Reviews: Resistance Training for Children and Adolescents

Although much of what we understand about the stimulus of resistance exercise has been gained by exploring the responses of adults to various training protocols, research into the effects of resistance exercise on children and adolescents has increased over the past decade. Despite outdated concerns that resistance training was ineffective or unsafe for youth, research increasingly suggests that resistance training can be a safe and effective method of exercise for children and adolescents provided that appropriate training guidelines are followed. In addition to enhancing motor skills and sports performance, regular participation in a youth resistance training program has the potential to positively influence several measurable indices of health. It helps strengthen bone, facilitate weight control, enhance psychosocial well-being, and improve one's cardiovascular risk profile. Furthermore, a stronger musculoskeletal system will enable boys and girls to perform life's daily activities with more energy and vigor and may increase a young athlete's resistance to sports-related injuries. Along with other types of physical activity, a properly designed youth resistance training program can offer observable health value to children and adolescents when appropriately prescribed and supervised.

Bone Mass and Strength in School-Age Children Exhibit Sexual Dimorphism Related to Differences in Lean Mass: The Generation R Study

Bone strength, a key determinant of fracture risk, has been shown to display clear sexual dimorphism after puberty. We sought to determine whether sex differences in bone mass and hip bone geometry as an index of strength exist in school-age prepubertal children and the degree to which the differences are independent of body size and lean mass. We studied 3514 children whose whole-body and hip scans were measured using the same densitometer (GE-Lunar iDXA) at a mean age of 6.2 years. Hip dual-energy X-ray absorptiometry (DXA) scans underwent hip structural analyses (HSA) with derivation of bone strength indices. Sex differences in these parameters were assessed by regression models adjusted for age, height, ethnicity, weight, and lean mass fraction (LMF). Whole-body bone mineral density (BMD) and bone mineral content (BMC) levels were 1.3% and 4.3% higher in girls after adjustment by LMF. Independent of LMF, boys had 1.5% shorter femurs, 1.9% and 2.2% narrower shaft and femoral neck with 1.6% to 3.4% thicker cortices than girls. Consequent with this geometry configuration, girls observed 6.6% higher stresses in the medial femoral neck than boys. When considering LMF, the sexual differences on the derived bone strength indices were attenuated, suggesting that differences in muscle loads may reflect an innate disadvantage in bone strength in girls, as consequence of their lower muscular acquisition. In summary, we show that bone sexual dimorphism is already present at 6 years of age, with boys having stronger bones than girls, the relation of which is influenced by body composition and likely attributable to differential adaptation to mechanical loading. Our results support the view that early life interventions (ie, increased physical activity) targeted during the pre- and peripubertal stages may be of high importance, particularly in girls, because before puberty onset, muscle mass is strongly associated with bone density and geometry in children. © 2015 American Society for Bone and Mineral Research.

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.

The impact of long-term school-based physical activity interventions on body mass index of primary school children - a meta-analysis of randomized controlled trials

Background

Physical activity (PA) intervention is a commonly recommended strategy to combat childhood obesity. However, its effectiveness has long been controversial. This paper aims to examine the effectiveness of long-term (≥12 months) school-based PA interventions on body mass index (BMI) in primary school children, who are gaining BMI.

Methods

Original papers were retrieved from PubMed, Google Scholar, the Cochrane Library and Web of Science, published between 1990 and 2015. The inclusion criteria were those research studies that were: randomized controlled trials (RCTs), conducted in primary school settings, had valid data on BMI at baseline and at the final follow up (or on BMI changes), and involved PA intervention that lasted for at least 12 months.

Results

Out of 11,158 potentially eligible articles, 18 papers were included in the analysis, involving 22,381 primary school children with intervention durations ranging from 12 to 72 months. Compared to the control groups, the BMI increment was 2.23 kg/m² less in the intervention groups (p < 0.05). The heterogeneity was high across the studies (99.8 %), but declined after sub-group analyses. The intervention type, intervention duration, and weekly PA intervention time were among the factors leading to the heterogeneity.

Conclusion

Long-term school-based interventions containing PA as a core component appear to be effective in achieving healthier BMI. However, the results should be interpreted with caution due to the high heterogeneity among the studies. More high quality school-based RCTs among diverse populations are needed to improve the homogeneity and to yield a more robust conclusion.

DNA methylation and the social gradient of osteoporotic fracture: A conceptual model

INTRODUCTION

Although there is a documented social gradient for osteoporosis, the underlying mechanism(s) for that gradient remain unknown. We propose a conceptual model based upon the allostatic load theory, to suggest how DNA methylation (DNAm) might underpin the social gradient in osteoporosis and fracture. We hypothesise that social disadvantage is associated with priming of inflammatory pathways mediated by epigenetic modification that leads to an enhanced state of inflammatory reactivity and oxidative stress, and thus places socially disadvantaged individuals at greater risk of osteoporotic fracture.

METHODS/RESULTS

Based on a review of the literature, we present a conceptual model in which social disadvantage increases stress throughout the lifespan, and engenders a proinflammatory epigenetic signature, leading to a heightened inflammatory state that increases risk for osteoporotic fracture in disadvantaged groups that are chronically stressed.

CONCLUSIONS

Our model proposes that, in addition to the direct biological effects exerted on bone by factors such as physical activity and nutrition, the recognised socially patterned risk factors for osteoporosis also act via epigenetic-mediated dysregulation of inflammation. DNAm is a dynamic modulator of gene expression with considerable relevance to the field of osteoporosis. Elucidating the extent to which this epigenetic mechanism transduces the psycho-social environment to increase the risk of osteoporotic fracture may yield novel entry points for intervention that can be used to reduce individual and population-wide risks for osteoporotic fracture. Specifically, an epigenetic evidence-base may strengthen the importance of lifestyle modification and stress reduction programs, and help to reduce health inequities across social groups.

MINI ABSTRACT

Our conceptual model proposes how DNA methylation might underpin the social gradient in osteoporotic fracture. We suggest that social disadvantage is associated with priming of inflammatory signalling pathways, which is mediated by epigenetic modifications, leading to a chronically heightened inflammatory state that places disadvantaged individuals at greater risk of osteoporosis.

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.

Physiological adaptations to resistance training in prepubertal boys

PURPOSE

The purpose of this study was to investigate the physiological adaptations of resistance training (RT) in prepubertal boys.

METHODS

Eighteen healthy boys were divided into RT (n = 9, Mage = 10.4 ± 0.5 years) and control (CTR; n = 9, Mage = 10.9 ± 0.7 years) groups. The RT group underwent a resistance training during 12 weeks, 3 times per week, performing 3 sets of 6 to 15 repetitions at intensities ranging from 60% to 80% of maximal dynamic strength (1-repetition maximum [1-RM] values). Before and after the training, the groups were assessed in their body mass and composition (dual-energy X-ray absorptiometry), isokinetic dynamometry, 1-RM, and ergoespirometry. Moreover, force per unit of muscle volume was calculated by the quotient between 1-RM and lean mass.

RESULTS

Both groups presented statistically significant (p < .05) increases in the 1-RM and force per unit of muscle volume in the knee extension and elbow flexion, but these strength increases were statistically significantly greater in the RT group (effect size [ES] = 2.83-9.00) than in the CTR group (ES = 0.72-1.00). Moreover, both groups statistically significantly increased in lean body mass variables (ES = 0.12-0.38). However, increases in the fat mass variables occurred only in the CTR group (ES = - 0.01-0.50), whereas no changes were observed in the RT group. Furthermore, there were statistically significant increases in all bone mineral content variables (ES = 0.13-0.43), without differences between groups. No cardiorespiratory changes were observed.

CONCLUSION

Twelve weeks of RT was effective in improving strength and force per unit of muscle volume and prevented fat mass increases in boys.

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.

The longitudinal effects of physical activity and dietary calcium on bone mass accrual across stages of pubertal development

Childhood and adolescence are critical periods of bone mineral content (BMC) accrual that may have long-term consequences for osteoporosis in adulthood. Adequate dietary calcium intake and weight-bearing physical activity are important for maximizing BMC accrual. However, the relative effects of physical activity and dietary calcium on BMC accrual throughout the continuum of pubertal development in childhood remains unclear. The purpose of this study was to determine the effects of self-reported dietary calcium intake and weight-bearing physical activity on bone mass accrual across the five stages of pubertal development in a large, diverse cohort of US children and adolescents. The Bone Mineral Density in Childhood study was a mixed longitudinal study with 7393 observations on 1743 subjects. Annually, we measured BMC by dual-energy X-ray absorptiometry (DXA), physical activity and calcium intake by questionnaire, and pubertal development (Tanner stage) by examination for up to 7 years. Mixed-effects regression models were used to assess physical activity and calcium intake effects on BMC accrual at each Tanner stage. We found that self-reported weight-bearing physical activity contributed to significantly greater BMC accrual in both sexes and racial subgroups (black and nonblack). In nonblack males, the magnitude of the activity effect on total body BMC accrual varied among Tanner stages after adjustment for calcium intake; the greatest difference between high- and low-activity boys was in Tanner stage 3. Calcium intake had a significant effect on bone accrual only in nonblack girls. This effect was not significantly different among Tanner stages. Our findings do not support differential effects of physical activity or calcium intake on bone mass accrual according to maturational stage. The study demonstrated significant longitudinal effects of weight-bearing physical activity on bone mass accrual through all stages of pubertal development.

Increased resistance during jump exercise does not enhance cortical bone formation

PURPOSE

This study sought to elucidate the effects of a low- and high-load jump resistance exercise (RE) training protocol on cortical bone of the tibia and femur mid-diaphyses.

METHODS

Sprague-Dawley rats (male, 6 months old) were randomly assigned to high-load RE (HRE; n = 16), low-load RE (LRE; n = 15), or cage control (CC; n = 11) groups. Animals in the HRE and LRE groups performed 15 sessions of jump RE for 5 wk. Load in the HRE group was progressively increased from 80 g added to a weighted vest (50 repetitions) to 410 g (16 repetitions). The LRE rats completed the same protocol as the HRE group (same number of repetitions), with only a 30-g vest applied.

RESULTS

Low- and high-load jump RE resulted in 6%-11% higher cortical bone mineral content and cortical bone area compared with controls, as determined by in vivo peripheral quantitative computed tomography measurements. In the femur, however, only LRE demonstrated improvements in cortical volumetric bone mineral density (+11%) and cross-sectional moment of inertia (+20%) versus the CC group. The three-point bending to failure revealed a marked increase in tibial maximum force (25%-29%), stiffness (19%-22%), and energy to maximum force (35%-55%) and a reduction in elastic modulus (-11% to 14%) in both LRE and HRE compared with controls. Dynamic histomorphometry assessed at the tibia mid-diaphysis determined that both LRE and HRE resulted in 20%-30% higher periosteal mineralizing surface versus the CC group. Mineral apposition rate and bone formation rate were significantly greater in animals in the LRE group (27%, 39%) than those in the HRE group.

CONCLUSION

These data demonstrate that jump training with minimal loading is equally, and sometimes more, effective at augmenting cortical bone integrity compared with overload training in skeletally mature rats.

An in-school exercise intervention to enhance bone and reduce fat in girls: the CAPO Kids trial

The CAPO Kids trial was a 9-mo, controlled, school-based intervention to examine the effects of a novel, brief, high intensity exercise regime on indices of musculoskeletal and metabolic health in pre- and early-pubertal girls.

METHODS

A total of 151 pre- and early-pubertal girls (10.6±0.6years), recruited from two different schools consented to participate; 76 in the exercise group (EX) and 75 in the control group (CON). EX performed 10min bouts of thrice-weekly jumping plus capoeira (a Brazilian sport that combines martial art with dance), along with usual physical education (PE) activities. CON continued usual PE alone. Maturity, weight, height, waist circumference, resting heart rate and blood pressure, maximal vertical jump, and aerobic capacity were determined using standard clinical and field measures. Calcaneal broadband ultrasound attenuation (BUA) and stiffness index (SI) were determined from quantitative ultrasonometry. A subsample of children also underwent DXA and pQCT measures. Prior physical activity participation and daily calcium consumption were determined from validated instruments.

RESULTS

EX girls improved BUA more than CON (+4.5% vs. +1.4%, p=0.019). Resting heart rate (-7.2% vs. -1.8%, p<0.01), maximal vertical jump (+13.4% vs. -1.2%, p<0.001), estimated maximal oxygen consumption (+10.6% vs. +1.0%, p<0.001), and waist circumference (+2.7% vs. +5.6%, p<0.001) also improved more for EX than CON.

CONCLUSION

Ten minutes of high intensity exercise (capoeira and jumping) three times a week in the primary school setting enhances musculoskeletal and metabolic outcomes in pre- and early-pubertal girls without disrupting the academic schedule. The programme, amenable to broad-scale school implementation, would confer meaningful public health benefits.

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.

Physical activity and bone mineral accrual in boys with different body mass parameters during puberty: a longitudinal study

The aim of our longitudinal study was to investigate the relationships between physical activity and bone mass in boys with different body mass status during the years surrounding pubertal growth spurt. Two hundred and six boys entering puberty took part in this study. The subjects were divided into underweight (BMI < 15.35), normal weight (BMI ≥ 15.35-21.22), overweight (BMI ≥ 21.22-26.02) and obese (BMI > 26.02) groups at baseline according to age related categories. Whole-body DXA scans were performed at baseline, after 12 and 24 months to assess body composition (lean body mass, fat mass), and total body (TB), lumbar spine (LS) and femoral neck (FN) bone mineral density (BMD) parameters. Physical activity was measured by 7-day accelerometry. For longitudinal analysis, multilevel fixed effects regression models were constructed. Biological age, height and lean body mass had an effect for explanation of TB BMD, FN BMD and LS BMD. Moderate to vigorous physical activity (MVPA), vigorous physical activity (VPA) and sedentary time (SED) had the significant effect only on FN BMD. Being an underweight boy at the baseline indicated greater chance (p<0.01) to have lower TB BMD in the future (2 years at follow up) development, compared to normal weight (estimates = -0.038), overweight (estimates = -0.061) and obese boys (estimates = -0.106).

Influence of physical activity on bone strength in children and adolescents: a systematic review and narrative synthesis

A preponderance of evidence from systematic reviews supports the effectiveness of weight-bearing exercises on bone mass accrual, especially during the growing years. However, only one systematic review (limited to randomized controlled trials) examined the role of physical activity (PA) on bone strength. Thus, our systematic review extended the scope of the previous review by including all PA intervention and observational studies, including organized sports participation studies, with child or adolescent bone strength as the main outcome. We also sought to discern the skeletal elements (eg, mass, structure, density) that accompanied significant bone strength changes. Our electronic-database, forward, and reference searches yielded 14 intervention and 23 observational studies that met our inclusion criteria. We used the Effective Public Health Practice Project (EPHPP) tool to assess the quality of studies. Due to heterogeneity across studies, we adopted a narrative synthesis for our analysis and found that bone strength adaptations to PA were related to maturity level, sex, and study quality. Three (of five) weight-bearing PA intervention studies with a strong rating reported significantly greater gains in bone strength for the intervention group (3% to 4%) compared with only three significant (of nine) moderate intervention studies. Changes in bone structure (eg, bone cross-sectional area, cortical thickness, alone or in combination) rather than bone mass most often accompanied significant bone strength outcomes. Prepuberty and peripuberty may be the most opportune time for boys and girls to enhance bone strength through PA, although this finding is tempered by the few available studies in more mature groups. Despite the central role that muscle plays in bones' response to loading, few studies discerned the specific contribution of muscle function (or surrogates) to bone strength. Although not the focus of the current review, this seems an important consideration for future studies.

Bone quality: the determinants of bone strength and fragility

Bone fragility is a major health concern, as the increased risk of bone fractures has devastating outcomes in terms of mortality, decreased autonomy, and healthcare costs. Efforts made to address this problem have considerably increased our knowledge about the mechanisms that regulate bone formation and resorption. In particular, we now have a much better understanding of the cellular events that are triggered when bones are mechanically stimulated and how these events can lead to improvements in bone mass. Despite these findings at the molecular level, most exercise intervention studies reveal either no effects or only minor benefits of exercise programs in improving bone mineral density (BMD) in osteoporotic patients. Nevertheless, and despite that BMD is the gold standard for diagnosing osteoporosis, this measure is only able to provide insights regarding the quantity of bone tissue. In this article, we review the complex structure of bone tissue and highlight the concept that its mechanical strength stems from the interaction of several different features. We revisited the available data showing that bone mineralization degree, hydroxyapatite crystal size and heterogeneity, collagen properties, osteocyte density, trabecular and cortical microarchitecture, as well as whole bone geometry, are determinants of bone strength and that each one of these properties may independently contribute to the increased or decreased risk of fracture, even without meaningful changes in aBMD. Based on these findings, we emphasize that while osteoporosis (almost) always causes bone fragility, bone fragility is not always caused just by osteoporosis, as other important variables also play a major role in this etiology. Furthermore, the results of several studies showing compelling data that physical exercise has the potential to improve bone quality and to decrease fracture risk by influencing each one of these determinants are also reviewed. These findings have meaningful clinical repercussions as they emphasize the fact that, even without leading to improvements in BMD, exercise interventions in patients with osteoporosis may be beneficial by improving other determinants of bone strength.

The bone tissue of children and adolescents with Down syndrome is sensitive to mechanical stress in certain skeletal locations: a 1-year physical training program study

The systemic complications of Down syndrome (DS) attenuate the osteogenic response to physical activity in DS patients. Through an interventional study we showed the effects of physical training on development of bone mineral content (BMC) and density (BMD) as well as on quantitative bone ultrasound (QUS) parameters in individuals with DS. A total of 42 children with DS were randomly assigned to either an exercising (DS-E, n=20, age 16 ± 1.8 years) or non-exercising group (DS-NE, n=22, age 16.9 ± 1.5 years). DS-E group was assigned to a program of osteogenic activities with 60 min sessions twice a week, over 12 month period. Bone mass measures were performed by dual X-ray absorpsiometry (DXA) at the spine and hip, and ultrasound attenuation (BUA) and velocity (SOS) assessed from the calcaneus by QUS device. All bone parameters had evolved with age, except for neck BMD. One year of training increased BMC values at lumbar spine (7%, p<.005) and total hip (10%, p<.05), and BMD values only at lumbar spine (4%, p<.05). Changes in BUA and SOS values were not evident following training. Trained individuals increased their motor skills measured through Eurofit tests. It was concluded that a program of osteogenic physical training may induce bone improvement in children with DS, but with a lower magnitude than that reported in the specialized literature for individuals without DS.

A 6-year exercise program improves skeletal traits without affecting fracture risk: a prospective controlled study in 2621 children

Most pediatric exercise intervention studies that evaluate the effect on skeletal traits include volunteers and follow bone mass for less than 3 years. We present a population-based 6-year controlled exercise intervention study in children with bone structure and incident fractures as endpoints. Fractures were registered in 417 girls and 500 boys in the intervention group (3969 person-years) and 835 girls and 869 boys in the control group (8245 person-years), all aged 6 to 9 years at study start, during the 6-year study period. Children in the intervention group had 40 minutes daily school physical education (PE) and the control group 60 minutes per week. In a subcohort with 78 girls and 111 boys in the intervention group and 52 girls and 54 boys in the control group, bone mineral density (BMD; g/cm(2) ) and bone area (mm(2) ) were measured repeatedly by dual-energy X-ray absorptiometry (DXA). Peripheral quantitative computed tomography (pQCT) measured bone mass and bone structure at follow-up. There were 21.7 low and moderate energy-related fractures per 1000 person-years in the intervention group and 19.3 fractures in the control group, leading to a rate ratio (RR) of 1.12 (0.85, 1.46). Girls in the intervention group, compared with girls in the control group, had 0.009 g/cm(2) (0.003, 0.015) larger gain annually in spine BMD, 0.07 g (0.014, 0.123) larger gain in femoral neck bone mineral content (BMC), and 4.1 mm(2) (0.5, 7.8) larger gain in femoral neck area, and at follow-up 24.1 g (7.6, 40.6) higher tibial cortical BMC (g) and 23.9 mm(2) (5.27, 42.6) larger tibial cross-sectional area. Boys with daily PE had 0.006 g/cm(2) (0.002, 0.010) larger gain annually in spine BMD than control boys but at follow-up no higher pQCT values than boys in the control group. Daily PE for 6 years in at study start 6- to 9-year-olds improves bone mass and bone size in girls and bone mass in boys, without affecting the fracture risk.

Effect of intervention programs in schools to reduce screen time: a meta-analysis

OBJECTIVE

to evaluate the effects of intervention program strategies on the time spent on activities such as watching television, playing videogames, and using the computer among schoolchildren.

SOURCES

a search for randomized controlled trials available in the literature was performed in the following electronic databases: PubMed, Lilacs, Embase, Scopus, Web of Science, and Cochrane Library using the following Keywords randomized controlled trial, intervention studies, sedentary lifestyle, screen time, and school. A summary measure based on the standardized mean difference was used with a 95% confidence interval.

DATA SYNTHESIS

a total of 1,552 studies were identified, of which 16 were included in the meta-analysis. The interventions in the randomized controlled trials (n=8,785) showed a significant effect in reducing screen time, with a standardized mean difference (random effect) of: -0.25 (-0.37, -0.13), p<0.01.

CONCLUSION

interventions have demonstrated the positive effects of the decrease of screen time among schoolchildren.

Physical activity programs for promoting bone mineralization and growth in preterm infants

BACKGROUND

Lack of physical stimulation may contribute to metabolic bone disease of preterm infants, resulting in poor bone mineralization and growth. Physical activity programs combined with adequate nutrition might help to promote bone mineralization and growth.

OBJECTIVES

The primary objective was to assess whether physical activity programs in preterm infants improve bone mineralization and growth and reduce the risk of fracture.The secondary objectives included other potential benefits in terms of length of hospital stay, skeletal deformities and neurodevelopmental outcomes, and adverse events.Subgroup analysis:• Given that the smallest infants are most vulnerable for developing osteopenia (Bishop 1999), a subgroup analysis was planned for infants with birth weight < 1000 g.• Calcium and phosphorus intake may affect an infant's ability to increase bone mineral content (Kuschel 2004). Therefore, an additional subgroup analysis was planned for infants receiving different amounts of calcium and phosphorus, along with full enteral feeds as follows. ∘ Below 100 mg/60 mg calcium/phosphorus or equal to/above 100 mg/60 mg calcium/phosphorus per 100 mL milk. ∘ Supplementation of calcium without phosphorus. ∘ Supplementation of phosphorus without calcium.

SEARCH METHODS

The standard search strategy of the Cochrane Neonatal Review Group (CNRG) was used. The search included the Cochrane Central Register of Controlled Trials (CENTRAL) (2012, Issue 9), MEDLINE, EMBASE, CINAHL (1966 to March 2013), and cross-references, as well as handsearching of abstracts of the Society for Pediatric Research and the International Journal of Sports Medicine.

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials comparing physical activity programs (extension and flexion, range-of-motion exercises) versus no organized physical activity programs in preterm infants.

DATA COLLECTION AND ANALYSIS

Data collection, study selection, and data analysis were performed according to the methods of the CNRG.

MAIN RESULTS

Eleven trials enrolling 324 preterm infants (gestational age 26 to 34 weeks) were included in this review. All were small (N = 16 to 50) single-center studies that evaluated daily physical activity for three and one-half to eight weeks during initial hospitalization. Methodological quality and reporting of included trials were variable.Four trials demonstrated moderate short-term benefits of physical activity for bone mineralization at completion of the physical activity program. The only trial assessing long-term effects on bone mineralization showed no effect of physical activity administered during initial hospitalization on bone mineralization at 12 months corrected age. Meta-analysis from four trials demonstrated a positive effect of physical activity on daily weight gain (weighted mean difference (WMD) 2.21 g/kg/d, 95% confidence interval (CI) 1.23 to 3.19). Data from four trials showed a positive effect on linear growth (WMD 0.12 cm/wk, 95% CI 0.01 to 0.24) but not on head growth (WMD -0.03 cm/wk, 95% CI -0.14 to 0.08) during the study period. Only one trial reported on fractures (this outcome did not occur in intervention and control groups) and complications of preterm birth (no significant differences between intervention and control groups). None of the trials assessed other outcomes relevant to this review.

AUTHORS' CONCLUSIONS

Some evidence suggests that physical activity programs might promote short-term weight gain and bone mineralization in preterm infants. Data are inadequate to allow assessment of harm or long-term effects. Current evidence does not support the routine use of physical activity programs in preterm infants. Further trials incorporating infants with a high baseline risk of osteopenia are required. These trials should address adverse events, long-term outcomes, and the effects of nutritional intake (calories, protein, calcium, phosphorus).