Physical activity and bone health in schoolchildren: the mediating role of fitness and body fat

Trajectories of osteogenic physical activity in children and adolescents: A 3-year cohort study

OBJECTIVES

We explored the latent profiles based on locomotor skills and cardiorespiratory fitness in Finnish schoolchildren and examined their associations with latent growth curves of osteogenic physical activity (PA) over three years.

DESIGN

Prospective cohort study.

METHODS

Altogether 1147 Finnish adolescents aged 11-13 years participated in the study. Osteogenic PA in terms of osteogenic index (OI) was calculated based on acceleration peak histograms using all of the peaks with acceleration >1.3 g. Locomotor skills were assessed using the five-leap and side-to-side jumping tests and cardiorespiratory fitness (CRF) using 20-metre shuttle run test. The latent growth curve models for the locomotor skills and cardiorespiratory fitness profiles were tested to examine the longitudinal development of OI scores over time three years (from T0 to T3).

RESULTS

OI scores were lower amongst children in the "Low locomotor profile" compared with "Moderate" and "High locomotor" profiles. The OI scores linearly decreased from T0 to T3 in each locomotor profile and the decrease was similar in all the profiles. Moreover, OI scores were lower in the "Low CRF profile" compared with "Moderate" and "High CRF" profiles. The OI scores decreased in each profile over time, but the decrease was steepest in the "Low CRF profile", whereas "Moderate" and "High CRF profiles" had similar developmental trajectories.

CONCLUSIONS

Children with the highest locomotor skills and higher CRF accumulate more osteogenic PA than their least skilful and fit peers, which can have important implications on bone health in this critical period for bone growth.

Cardiorespiratory Fitness and Bone Turnover Markers in Adults With Metabolic Syndrome: The Mediator Role of Inflammation

The relationship between inflammatory markers and bone turnover in adults is well known, and a negative association between cardiorespiratory fitness (CRF) and inflammatory markers has also been described. Hence, we tested whether the association between CRF and bone turnover markers is mediated by inflammatory markers in adults with metabolic syndrome. A total of 81 adults (58.5 ± 5.0 years, 62.7% women) were included in the analysis. CRF was measured by the 6-min walking test. Serum interleukin (IL)-1β, IL-6, IL-10, tumor necrosis factor alpha, high-sensitivity c-reactive protein (hsCRP) and vascular endothelial growth factor, collagen type I cross-linked C-telopeptide, procollagen type I N-terminal propeptide (P1NP), and total osteocalcin were assessed using a sensitive ELISA kit. Body composition was assessed by dual-energy X-ray absorptiometry. Partial correlation was used to test the relationship between CRF, inflammatory markers, and bone turnover markers, controlling for sex, lean mass, and fat mass. Boot-strapped mediation procedures were performed, and indirect effects with confidence intervals not including zero were interpreted as statistically significant. CRF was positively correlated with P1NP levels (r = .228, p = .044) and osteocalcin levels (r = .296, p = .009). Furthermore, CRF was positively correlated with IL-1β levels (r = .340, p = .002) and negatively correlated with hsCRP levels (r = -.335, p = .003), whereas IL-1β levels were positively correlated with P1NP levels (r = .245, p = .030), and hsCRP levels were negatively correlated with P1NP levels (r = -.319, p = .004). Finally, the association between CRF and P1NP levels was totally mediated by hsCRP (percentage of mediation = 39.9). Therefore, CRF benefits on bone formation could be dependent on hsCRP concentrations in this population.

A comparison of the associations between bone health and three different intensities of accelerometer-derived habitual physical activity in children and adolescents: a systematic review

Positive associations have been identified between bone outcomes and accelerometer-derived moderate (MPA) and vigorous (VPA) physical activity (PA) in youth; however, it remains unclear which intensity is most beneficial. This systematic review aimed to summarise accelerometer-derived methods used to estimate habitual PA in children and adolescents and determine whether the magnitude of association was consistently stronger for a particular intensity (MPA/MVPA/VPA). Observational studies assessing associations between accelerometer-derived MPA and/or MVPA and VPA with bone outcomes in children and adolescents (≤ 18 years) were identified in MEDLINE, EMBASE, Web of Science, SPORTDiscus and the Cochrane Central Register of Controlled Trials. Thirty articles were included (total n = 20,613 (10,077 males), 4-18 years). Chi-square tests determined whether the proportion of significant associations and strongest within-study associations differed significantly between intensities. Results demonstrated that accelerometer methods were highly variable between studies. Of the 570 associations analysed, 186 were significant (p < 0.05). The proportion of within-study strongest associations differed by PA intensity (3 × 2 χ2 = 86.6, p < 0.001) and was significantly higher for VPA (39%) compared to MVPA (5%; 2 × 2 χ2 = 55.3, p < 0.001) and MPA (9%, 2 × 2 χ2 = 49.1, p < 0.001). Results indicated a greater benefit of VPA over MPA/MVPA; however, variability in accelerometer-derived methods used prevents the precise bone-benefitting amount of VPA from being identified. Long epochs and numerous intensity cut-point definitions mean that bone-relevant PA has likely been missed or misclassified in this population. Future research should explore the use of shorter epochs (1 s) and identify bone-specific activity intensities, rather than using pre-defined activity classifications more relevant to cardiovascular health.

The "Fat but Fit" Paradigm and Bone Health in Young Adults: A Cluster Analysis

The fat but fit paradox has suggested that obese individuals with good fitness levels have lower cardiometabolic risk compared to individuals with normal weight but lower fitness levels. This paradigm has not been explored in the context of bone health. The aim of this study was to test whether categories of fat but fit paradigm assessed by body fat percentage and handgrip strength holds up in young adults and to analyze the relationship between fat but fit categories and bone outcomes. Cluster cross-sectional analyses of data from 499 young adults aged 18 to 30 from Toledo and Cuenca, Spain were conducted. Body fat percentage, handgrip strength, bone mineral content (BMC), bone mineral density (BMD), and dietary nutrients such as, proteins, magnesium, calcium, phosphorus, potassium, and vitamin D were assessed. Cluster analysis of body fat percentage and handgrip z scores resulted in a classification of four clusters that could be interpreted according to Fat Unfit (FU), Unfat Unfit (UU), Fat Fit (FF) and Unfat Fit (UF) categories. ANCOVA models showed that young adults in clusters with higher handgrip strength levels (FF, UF) and with higher key bone nutrients levels (UF) had significantly higher total BMC values than their peers in the UU and FU cluster categories, after controlling for sex, age and height. This study provides two novel conclusions in relation to the fat but fit paradigm: first, it confirms the construct of the four clusters of body fat percentage and handgrip strength, and second, it reinforces the predictive validity of the fat but fit paradigm categories, indicating the positive effect, although it may not just be a causal relationship, of muscular strength and key bone nutrients on counteracting the negative effect of obesity on bone health.

Association of objectively measured physical activity and bone health in children and adolescents: a systematic review and narrative synthesis

The influence of day-to-day physical activity on bone in adolescence has not been well characterized. Forty articles were identified that assessed the relationship between accelerometry-derived physical activity and bone outcomes in adolescents. Physical activity was positively associated with bone strength in peri-pubertal males, with less consistent evidence in females. Physical activity (PA) is recommended to optimize bone development in childhood and adolescence; however, the influence of day-to-day PA on bone development is not well defined. The aim of this review was to describe the current evidence for objectively measured PA on bone outcomes in healthy children and adolescents. MEDLINE, Embase, Cochrane Library, Scopus, Web of Science, CINAHL, PsycInfo, and ClinicalTrials.gov were searched for relevant articles up to April 2020. Studies assessing the relationship between accelerometry-derived PA and bone outcomes in adolescents (6-18 years old) were included. Two reviewers independently screened studies for eligibility, extracted data, and rated study quality. Forty articles met inclusion criteria (25 cross-sectional, 15 longitudinal). There was significant heterogeneity in accelerometry methodology and bone outcomes measured. Studies in males indicated a significant, positive relationship between moderate to vigorous PA (MVPA) and bone outcomes at the hip and femur, particularly during the peri-pubertal years. The results for MVPA and bone outcomes in females were mixed. There was a paucity of longitudinal studies using pQCT and a lack of data regarding how light PA and/or impact activity influences bone outcomes. The current evidence suggests that objectively measured MVPA is positively associated with bone outcomes in children and adolescents, especially in males. However, inconsistencies in methodology make it difficult to determine the amount and type of PA that leads to favorable bone outcomes. Given that the majority of research has been conducted in Caucasian adolescents, further research is needed in minority populations.

Body Composition as a Mediator between Cardiorespiratory Fitness and Bone Mass during Growth

INTRODUCTION AND PURPOSE

To examine the effect of cardiorespiratory fitness (CRF) and muscle power output (MPO) on bone mass of prepubertal and pubertal children using lean mass (LM) and percentage of fat mass (%FM) as mediator variables. The hypothesis was that both LM and %FM would be independent mediators of the relationships during the sexual maturation period.

METHODS

We analyzed 200 children (88 boys and 112 girls [11.5 ± 2.0 yr]). Body composition was analyzed by bone densitometry, and indirect calorimetry and cycle ergometer were used to calculate V˙O2peak (mL·kg·min) and MPO (W) during an incremental exercise test. Sample was divided by pubertal status.

RESULTS

In the prepubertal group, LM and %FM acted independently as mediators in the relationship between bone mass and CRF or MPO (22%-25% for LM and 37%-50% for %FM, respectively). In pubertal children, LM acted as mediator at 37%.

CONCLUSIONS

Although the independent mediator role of LM and %FM in the associations between CRF or MPO and bone mass was present during the prepubertal stage, only LM remain its mediator role in these associations during the postpubertal period. Therefore, with growth and sexual maturation, the full effect of LM seems to increase, whereas the influence of %FM seems to disappear.

The risk of eating disorders and bone health in young adults: the mediating role of body composition and fitness

PURPOSE

To analyze the independent relationship between the risk of eating disorders and bone health and to examine whether this relationship is mediated by body composition and cardiorespiratory fitness (CRF).

METHODS

In this cross-sectional study, bone-related variables, lean mass, fat mass (by DXA), risk of eating disorders (SCOFF questionnaire), height, weight, waist circumference and CRF were measured in 487 university students aged 18-30 years from the University of Castilla-La Mancha, Spain. ANCOVA models were estimated to test mean differences in bone mass categorized by body composition, CRF or risk of eating disorders. Subsequently, linear regression models were fitted according to Baron and Kenny's procedures for mediation analysis.

RESULTS

The marginal estimated mean ± SE values of total body bone mineral density for the categories "no risk of eating disorders" and "risk of eating disorders" were 1.239 ± 0.126 < 1.305 ± 0.089, P = 0.021. However, this relationship disappeared after adjustment for any of the parameters of body composition or CRF. Therefore, all body composition parameters (except for lean mass) and CRF turned out to be full mediators in the association between the risk of eating disorders and bone health in young adults.

CONCLUSIONS

Body composition and CRF mediate the association between the risk of eating disorders and bone health. These findings highlight the importance of maintaining a healthy weight and good CRF for the prevention of the development of eating disorders and for the maintenance of good bone health in young adults.

LEVEL OF EVIDENCE

Level V, cross-sectional descriptive study.

Relationship between physical activity, dietary intake and bone parameters in 10-12 years old Hungarian boys and girls

OBJECTIVES

Physical activity (PA) and adequate macro- and micronutrient intake have favourable influence on the bone status. The aim of this study was to analyse the relationships among PA, anthropometric data, dietary intake and ultrasound bone characteristics in children.

METHODS

10-12 years old Hungarian children (N = 123, 59 girls, 64 boys) provided physical activity, diet, anthropometric and bone data. PA was measured with accelerometer (Actigraph GT3X+). Diet was evaluated with three-day, 24-hour food recall. Calcaneal quantitative ultrasound (QUS) bone parameters were registered with Sonost3000 bone densitometer.

RESULTS

Nutrition and anthropometry did not differ by gender. The values of broadband ultrasound attenuation (BUA) were significantly higher in boys. Girls spent significantly more time being sedentary, boys had greater light, moderate, vigorous, and moderate to vigorous physical activity (MVPA) levels. The children accumulated more than twice the suggested amount of public health guidelines for MVPA. QUS parameters correlated significantly with vigorous physical activity in boys, and with age, height, weight, fat percentage, and body mass index (BMI) for both genders. There was no significant relationship between nutrition and QUS; however, inadequate vitamin K intake correlated with less favourable bone parameters. Multiple linear regression analysis confirmed the importance of vigorous PA - speed of sound (SOS): β = 0.358, p = 0.006; BUA: β = 0.340, p = 0.007; bone quality index (BQI): β = 0.377, p = 0.002; vitamin K intake - SOS: β = 0.256, p = 0.025; BUA: β = 0.235, p = 0.033; BQI: β = 0.295, p = 0.007; BMI - SOS: β = 0.207, p = 0.064; BUA: β = 0.455, p < 0.001; BQI: β = 0.284, p = 0.008; and age - SOS: β = 0.450, p < 0.001; BUA: β = 0.318, p = 0.004; BQI: β = 0.444, p < 0.001).

CONCLUSIONS

Changes in the characteristics of ultrasound bone parameters among 10-12 years old children mainly depended on the amount of intense PA, adequate vitamin K intake and anthropometric variables related to age.

Agreement Between Dual-Energy X-Ray Absorptiometry and Quantitative Ultrasound to Evaluate Bone Health in Adolescents: The PRO-BONE Study

PURPOSE

The present study aims to investigate the association between dual-energy X-ray absorptiometry (DXA) and quantitative ultrasound (QUS) parameters and the intermethods agreement in active males.

METHODS

In this cross-sectional study, bone health (by DXA and calcaneal QUS), physical activity (by accelerometers), and anthropometrics measurements were assessed in 117 active adolescents (12-14 y old). Bivariate correlation coefficients were calculated to assess the relationships between DXA standard regions of interest and QUS parameters. Intraclass correlation coefficients and Bland-Altman plots were used to assess the level of agreement between bone mineral content regions derived from DXA and stiffness index. The measurements were z score transformed for comparison.

RESULTS

Most QUS parameters were positive and significantly correlated with DXA outcomes (stiffness index: r = .43-.52; broadband ultrasound attenuation: r = .50-.58; speed of sound: r = .25-.27) with the hip showing the highest correlations. Moreover, the present study found fair to good intraclass correlation coefficients of agreement (.60-.68) between DXA and QUS to assess bone health. The Bland-Altman analysis showed a limited percentage of outliers (3.2%-8.6%).

CONCLUSION

QUS device could represent an acceptable alternative method to assess bone health in active adolescent males.

Physical Fitness, Adiposity, and Diets as Surrogate Measures of Bone Health in Schoolchildren: A Biochemical and Cross-Sectional Survey Analysis

This study aimed to investigate the associations between adiposity, muscular fitness (MF), diet, sun exposure, and physical activity profiles as surrogate measures with bone health status in a sample of schoolchildren aged 8-18 yr old. A total of 250 Egyptian schoolchildren aged 8-18 yr were randomly invited to participate in these cross-sectional survey analyses. Calcaneal broadband ultrasound attenuation (c-BUA), bone mineral density (BMD), and bone formation markers (total calcium, serum bone alkaline phosphatase, and osteocalcin) were measured as markers of bone health. Adiposity profile, MF, physical activity (PA), sun exposure, Ca, and vitamin D dietary intake as related cofactors of bone health were measured by using prevalidated questionnaires and standard analytical techniques. A total of 85% (n = 213) of the study population showed normal bone health and 14.8% (n = 37) had abnormal bone health; most of them are girls (67.6%) classified according to BMD and c-BUA Z-scores into osteopenia (9.6%) and osteoporosis (5.2%). Compared with boys, higher correlations between c-BUA, bone mineral content, and BMD measures in the femoral neck, lumbar spine, whole body, and bone markers were reported in girls with lower bone mass. There was a positive significant correlation between body mass index, adiposity, sun exposure, MF, PA status, Ca and vitamin D intake, and c-BUA and BMD score analyses. These parameters were shown to be associated with about ~57.3%-88.4% of bone health characteristics of children and adolescents with osteopenia and osteoporosis. In children and adolescents, sun exposure, Ca and vitamin D diets, adiposity, PA, and changes in the levels of Ca, osteocalcin, and serum bone alkaline phosphatase were shown to be associated with bone health. Also, a significant correlation was reported between c-BUA score, dual-energy X-ray absorptiometry-BMD measures, and bone markers at clinically important bone sites of girls and boys. However, further clinical trials should be studied to consider c-BUA and bone markers as the benchmark estimates of bone mass for diagnostic purposes in young ages.

Insulin and bone health in young adults: The mediator role of lean mass

BACKGROUND

The positive relationship between lean mass (LM) and bone health is well known, but a positive association between insulin and LM has also been described. Insulin has some anabolic properties on bone through the stimulation of osteoblast differentiation, yet the role of LM as a confounder or mediator in this relationship remains uncertain.

OBJECTIVE

To examine whether the association between insulin levels and bone health is mediated by LM.

METHODS

A cross-sectional study was conducted at the Castilla La Mancha University (Spain) involving 466 young adults (113 young men; 19.5±2.3 years). LM and total-body bone mineral content (BMC) were measured by dual energy x-ray absorptiometry, and insulin was measured in fasting serum samples.

RESULTS

Young adults with high total LM had higher values of total-body BMC than their peers after controlling for age and sex, this relationship persisted after adjusting for insulin levels (p<0.001). In mediation analyses, insulin levels were positively associated with total-body BMC (b = 0.05; p<0.001) and total LM acted as an intermediate variable, attenuating the association between insulin levels and total-body BMC (b = -31.98; p>0.05) as indicated by Sobel test values for indirect effect (z = 4.43; p<0.001).

CONCLUSIONS

LM plays an important role in the relationship between insulin levels and bone health, in such a way that while increases in LM have a positive influence on bone health, they are also negatively associated with insulin levels.

Body Composition, Nutritional Profile and Muscular Fitness Affect Bone Health in a Sample of Schoolchildren from Colombia: The Fuprecol Study

The objective of the present study is to investigate the relationships between body composition, nutritional profile, muscular fitness (MF) and bone health in a sample of children and adolescents from Colombia. Participants included 1118 children and adolescents (54.6% girls). Calcaneal broadband ultrasound attenuation (c-BUA) was obtained as a marker of bone health. Body composition (fat mass and lean mass) was assessed using bioelectrical impedance analysis. Furthermore height, weight, waist circumference and Tanner stage were measured and body mass index (BMI) was calculated. Standing long-jump (SLJ) and isometric handgrip dynamometry were used respectively as indicators of lower and upper body muscular fitness. A muscular index score was also computed by summing up the standardised values of both SLJ and handgrip strength. Dietary intake and degree of adherence to the Mediterranean diet were assessed by a 7-day recall questionnaire for food frequency and the Kidmed questionnaire. Poor bone health was considered using a z-score cut off of ≤-1.5 standard deviation. Once the results were adjusted for age and Tanner stage, the predisposing factors of having a c-BUA z-score ≤-1.5 standard deviation included being underweight or obese, having an unhealthy lean mass, having an unhealthy fat mass, SLJ performance, handgrip performance, and unhealthy muscular index score. In conclusion, body composition (fat mass and lean body mass) and MF both influenced bone health in a sample of children and adolescents from Colombia. Thus promoting strength adaptation and preservation in Colombian youth will help to improve bone health, an important protective factor against osteoporosis in later life.