Pediatric Bone Mineral Accrual Study Research Articles

Clinical and psychosocial stress factors are associated with decline in physical activity over time in children with juvenile idiopathic arthritis

BackgroundPhysical activity (PA) patterns in children with juvenile idiopathic arthritis (JIA) over time are not well described. The aim of this study was to describe associations of physical activity (PA) with disease activity, function, pain, and psychosocial stress in the 2 years following diagnosis in an inception cohort of children with juvenile idiopathic arthritis (JIA).MethodsIn 82 children with newly diagnosed JIA, PA levels, prospectively determined at enrollment, 12 and 24 months using the Physical Activity Questionnaire for Children (PAQ-C) and Adolescents (PAQ-A) raw scores, were evaluated in relation to disease activity as reflected by arthritis activity (Juvenile Arthritis Disease Activity Score (JADAS-71)), function, pain, and psychosocial stresses using a linear mixed model approach. Results in the JIA cohort were compared to normative Pediatric Bone Mineral Accrual Study data derived from healthy children using z-scores.ResultsAt enrollment, PA z-score levels of study participants were lower than those in the normative population (median z-score − 0.356; p = 0.005). At enrollment, PA raw scores were negatively associated with the psychosocial domain of the Juvenile Arthritis Quality of Life Questionnaire (r = − 0.251; p = 0.023). There was a significant decline in PAQ-C/A raw scores from baseline (median and IQR: 2.6, 1.4–3.1) to 24 months (median and IQR: 2.1, 1.4–2.7; p = 0.003). The linear mixed-effect model showed that PAQ-C/A raw scores in children with JIA decreased as age, disease duration, and ESR increased. The PAQ-C/A raw scores of the participants was also negatively influenced by an increase in disease activity as measured by the JADAS-71 (p < 0.001).ConclusionCanadian children with newly diagnosed JIA have lower PA levels than healthy children. The decline in PA levels over time was associated with disease activity and higher disease-specific psychosocial stress.

Relationship Between Trajectories of Trunk Fat Development in Emerging Adulthood and Cardiometabolic Risk at 36 Years of Age.

This study examined trajectories of trunk fat mass (FM) accrual during emerging adulthood of individuals categorized, at 36 years of age, as having higher comparedwith lower scores of (1) metabolic risk and (2) blood pressure risk. Fifty-five individuals from the Saskatchewan Pediatric Bone Mineral Accrual Study (1991-2017) were assessed from adolescence (mean [SD], 11.5 [1.8] years) through emerging adulthood (26.2 [2.2]years) andinto early adulthood (35.6 [2.2] years) (median 11 visits per individual). Sex-specific median splits of continuous standardized risk scores at 36 years of age were created. Dual-energy x-ray absorptiometry-assessed trunk FM trajectories were analyzed using multilevel random effects models. Higher risk scores of blood pressure risk and metabolic risk had significantly steeper trajectories of fat development (0.45 [0.11] and 0.44 [0.11] log g, respectively) than the lower risk scores. Dietary fat was not related (P > 0.05). Physical activity was negatively related (-0.04 [0.02] physical activity score) to trunk FM development during emerging adulthood. Young adults with higher metabolic risk at 36 years of age had greater trunk FM development during both adolescence and emerging adulthood, supporting the need for intervention at both these critical periods of fat accrual.

Vegetarian-style dietary pattern during adolescence has long-term positive impact on bone from adolescence to young adulthood: a longitudinal study

BackgroundThe amount of bone accrued during adolescence is an important determinant of later osteoporosis risk. Little is known about the influence of dietary patterns (DPs) on the bone during adolescence and their potential long-term implications into adulthood. We examined the role of adolescent DPs on adolescent and young adult bone and change in DPs from adolescence to young adulthood.MethodsWe recruited participants from the Saskatchewan Pediatric Bone Mineral Accrual Study (1991–2011). Data from 125 participants (53 females) for adolescent analysis (age 12.7 ± 2 years) and 115 participants (51 females) for adult analysis (age 28.2 ± 3 years) were included. Bone mineral content (BMC) and areal bone mineral density (aBMD) of total body (TB), femoral neck (FN) and lumbar spine (LS) were measured using dual-energy X-ray absorptiometry. Adolescent dietary intake data from multiple 24-h recalls were summarized into 25 food group intakes and were used in the principal component analysis to derive DPs during adolescence. Associations between adolescent DPs and adolescent or adult BMC/BMD were analyzed using multiple linear regression and multivariate analysis of covariance while adjusting for sex, age, the age of peak height velocity, height, weight, physical activity and total energy intake. Generalized estimating equations were used for tracking DPs.ResultsWe derived five DPs including “Vegetarian-style”, “Western-like”, “High-fat, high-protein”, “Mixed” and “Snack” DPs. The “Vegetarian-style” DP was a positive independent predictor of adolescent TBBMC, and adult TBBMC, TBaBMD (P < 0.05). Mean adolescent TBaBMD and young adult TBBMC, TBaBMD, FNBMC and FNaBMD were 5%, 8.5%, 6%, 10.6% and 9% higher, respectively, in third quartile of “Vegetarian-style” DP compared to first quartile (P < 0.05). We found a moderate tracking (0.47–0.63, P < 0.001) in DP scores at individual levels from adolescence to adulthood. There were an upward trend in adherence to “Vegetarian-style” DP and an downward trend in adherence to “High-fat, high-protein” DP from adolescence to young adulthood (P < 0.01).ConclusionA “Vegetarian-style” DP rich in dark green vegetables, eggs, non-refined grains, 100% fruit juice, legumes/nuts/seeds, added fats, fruits and low-fat milk during adolescence is positively associated with bone health.

Tracking Dietary Patterns over 20 Years from Childhood through Adolescence into Young Adulthood: The Saskatchewan Pediatric Bone Mineral Accrual Study.

Dietary patterns established during adolescence might play a role in adulthood disease. We examined the stability of dietary patterns (DPs) from childhood through adolescence and into young adulthood (from age 8 to 34 years). Data from 130 participants (53 females) of Saskatchewan Pediatric Bone Mineral Accrual Study (aged 8–15 years, at baseline) were included. Multiple 24-h recalls were collected annually from 1991 to 1997, 2002 to 2005, and 2010 and 2011. Using principal component analysis, “Vegetarian-style”, “Western-like”, “High-fat, high-protein”, “Mixed”, and “Snack” DPs were derived at baseline. Applied DP scores for all annual measurements were calculated using factor loading of baseline DPs and energy-adjusted food group intakes. We analyzed data using generalized estimating equations. The tracking coefficient represents correlation between baseline dietary pattern scores and all other follow-up dietary pattern scores. We found a moderate tracking for the “Vegetarian-style” (β = 0.44, p < 0.001) and “High-fat, high-protein” (β = 0.39, p < 0.001) DPs in females and “Vegetarian-style” DP (β = 0.30, p < 0.001) in males. The remaining DPs showed poor-to-fair tracking in both sexes. No tracking for “Western-like” DP in females was observed. Assessing overall change in DP scores from childhood to young adulthood showed an increasing trend in adherence to “Vegetarian-style” DP and decreasing trend in adherence to “High-fat, high-protein” DP by age in both sexes (p < 0.001), while “Western-like” and “Mixed” DP scores increased only in males (p < 0.001). These findings suggest that healthy dietary habits established during childhood and adolescence moderately continue into adulthood.

Are milk and alternatives and fruit and vegetable intakes during adolescence associated with cortical and trabecular bone structure, density, and strength in adulthood?

The purpose of this study was to investigate whether adolescents with high intake of milk and alternatives (M&A) or fruit and vegetables (F&V) had better adult bone structure and strength compared to those with low intake levels. We analyzed data from 47 males and 69 females enrolled in the Pediatric Bone Mineral Accrual Study (PBMAS 1991-2011), who had one peripheral quantitative computed tomography scan at age 29 ± 2years. We measured radius and tibia shaft total area (ToA), cortical area (CoA), cortical content (CoC), cortical density, bone strength (SSIp), and muscle area, as well as distal radius and tibia ToA, total density, trabecular area, trabecular content, trabecular density, and bone strength (BSIc). Sequential 24-h recalls were used to assess M&A and F&V intake; participants were grouped for their mean intake during adolescence (low = bottom quartile, moderate = middle quartiles, high = top quartile) and were compared using multivariate analysis of covariance while adjusting for adult height, muscle area, physical activity, energy and calcium intake and adolescent energy intake, and physical activity. Females with high M&A intake compared to low M&A intake group (mean 3.8 vs. 1.3 servings/day, respectively) had greater adult ToA (14%, p < 0.05), CoA (15%, p < 0.01), and CoC (16%, p < 0.01) at radius shaft. Females with moderate F&V intake compared to low F&V intake group (mean 3.7 vs. 2.1 servings/day, respectively) had greater adult ToA (8.5%, p < 0.05) at distal tibia. Higher intake of M&A or F&V during adolescence had a long-term beneficial effect on bone structure in females, an association not observed in males.

Physical activity, bone mass and muscle strength in children

Physical activity, bone mass and muscle strength in children

Enhancing a Somatic Maturity Prediction Model.

Assessing biological maturity in studies of children is challenging. Sex-specific regression equations developed using anthropometric measures are widely used to predict somatic maturity. However, prediction accuracy was not established in external samples. Thus, we aimed to evaluate the fit of these equations, assess for overfitting (adjusting as necessary), and calibrate using external samples. We evaluated potential overfitting using the original Pediatric Bone Mineral Accrual Study (PBMAS; 79 boys and 72 girls; 7.5-17.5 yr). We assessed change in R and standard error of the estimate (SEE) with the addition of predictor variables. We determined the effect of within-subject correlation using cluster-robust variance and fivefold random splitting followed by forward-stepwise regression. We used dominant predictors from these splits to assess predictive abilities of various models. We calibrated using participants from the Healthy Bones Study III (HBS-III; 42 boys and 39 girls; 8.9-18.9 yr) and Harpenden Growth Study (HGS; 38 boys and 32 girls; 6.5-19.1 yr). Change in R and SEE was negligible when later predictors were added during step-by-step refitting of the original equations, suggesting overfitting. After redevelopment, new models included age × sitting height for boys (R, 0.91; SEE, 0.51) and age × height for girls (R, 0.90; SEE, 0.52). These models calibrated well in external samples; HBS boys: b0, 0.04 (0.05); b1, 0.98 (0.03); RMSE, 0.89; HBS girls: b0, 0.35 (0.04); b1, 1.01 (0.02); RMSE, 0.65; HGS boys: b0, -0.20 (0.02); b1, 1.02 (0.01); RMSE, 0.85; HGS girls: b0, -0.02 (0.03); b1, 0.97 (0.02); RMSE, 0.70; where b0 equals calibration intercept (standard error (SE)) and b1 equals calibration slope (SE), and RMSE equals root mean squared error (of prediction). We subsequently developed an age × height alternate for boys, allowing for predictions without sitting height. Our equations provided good fits in external samples and provide an alternative to commonly used models. Original prediction equations were simplified with no meaningful increase in estimation error.

The associations of exposure to combined hormonal contraceptive use on bone mineral content and areal bone mineral density accrual from adolescence to young adulthood: A longitudinal study

BackgroundThe association of long term combined hormone based contraceptives (CHC) use on bone mineral content (BMC) and areal bone mineral density (aBMD) development remains controversial, as it appears that the relationship may be age-dependent. The purpose of this study was to investigate the long-term associations of CHC exposure on the accrual of bone parameters from adolescence into young-adulthood. Methods110 women (67 exposed to CHC) were drawn from the Pediatric Bone Mineral Accrual Study (PBMAS). Serial measures of total body (TB), lumbar spine (LS) and femoral neck (FN) BMC and aBMD were assessed by DXA (a total of 950 scans) and aligned by biological age (BA, years from peak height velocity [PHV]). Multilevel random effects models were constructed to assess the time dependent associations between annual CHC exposure and the development of bone parameters. ResultsAfter BA, height, lean tissue mass, fat mass, calcium and vitamin D intake, and physical activity were controlled, it was observed that those individuals exposed to CHC 6-years post PHV developed significantly less (−0.00986±0.00422g/cm2) TB aBMD than their non CHC exposed peers. Additionally, there were significant BA by CHC exposure interactions, where CHC exposure 6-years or more post PHV resulted in developing less TB BMC (−4.94±2.41g), LS BMC (−0.29±0.11g) and LS aBMD (−0.00307±0.00109g/cm2). One year after the attainment of PHV, CHC users were predicted to have 1.2% more TB BMC, 3.8% more LS BMC and 1.7% more LS aBMD than non-users. At 9-years post PHV the predicted differences showed that CHC users had 0.9% less TB BMC and 2.7% less LS BMC and 1.6% less LS BMD than those not exposed to CHC. ConclusionsCHC may not hinder the development of BMC or aBMD during adolescence; however, exposure 6-years or more after PHV may be detrimental.

Do Food Group Intake and Physical Activity during Growth Spurt Have Impact on Bone Health during Adulthood

The amount of bone mass achieved during childhood to early adulthood is one the most important predictors of osteoporosis later in life. Since almost 25% of peak bone mass is attained during the 4‐year period around age at peak height velocity (APHV), we aimed to determine how milk and alternatives intake, fruit and vegetable (F&amp;V) intake and physical activity (PA) during 4‐year period around PHV (growth spurt) impact maximum total‐body bone mineral density (Max‐TBBMD) at least 10 years after age at PHV (adulthood).The Saskatchewan Pediatric Bone Mineral Accrual Study (BMAS 1991‐2011) data from 103 participants (55 female and 48 male) were used for this analysis. Data were collected using serial 24‐h recalls, PA questionnaire and dual‐energy X‐ray absorptiometry machine. Biological age was defined as the number of years after PHV. We analyzed data using stepwise linear regression.Among all modifiable factors, adulthood F&amp;V intake was a significant independent predictor of max‐TBBMD after adjusting for all potential variables (β=0.132 g/cm2; P =0.014). Mean intake of F&amp;V intake during adulthood was 4.82±2.58 serving/d with only 14.6% adequate intake. Other predictors were TBBMD at APHV, adulthood total body lean mass, height, and biological age at Max‐TBBMD.Beneficial effect of adulthood F&amp;V intake might be due to acid‐buffering effect and providing nutrients and natural compounds essential for bone mineral maintenance during adulthood.The source of the research support was Canadian Institutes of Health Research (CIHR).

Adolescent Physical Activity and Bone Strength at the Proximal Femurin Adulthood

Physical activity (PA) enhances bone structural strength at the proximal femur in adolescence, but whether these benefits are maintained into early adulthood remains unknown. The purpose of this study was to investigate whether males and females, described as active, average, and inactive during adolescence, display differences in structural strength at the proximal femur in early adulthood (20-30 yr). One hundred four participants (55 males and 49 females) from the Pediatric Bone Mineral Accrual Study (PBMAS) were categorized into adolescent PA groupings (inactive, average, and active) using the Physical Activity Questionnaire for Adolescents. Cross-sectional area and section modulus (Z) at the narrow neck, intertrochanter, and femoral shaft (S) sites of the proximal femur were assessed using hip structural analysis in young adulthood from femoral neck dual-energy x-ray absorptiometry scans. Group differences were assessed using ANCOVA, controlling for adult height (Ht), adult weight (Wt), adolescent bone geometry, sex, percentage adult total body lean tissue (LTM%), and adult PA levels. Active adolescents had significantly greater adjusted bone geometric measures at all sites than their inactive classified peers during adolescence (P < 0.05). In adulthood, when adjusted for Ht, Wt, adolescent bone geometry, sex, LTM%, and adult PA levels, adolescent participants categorized as active had significantly greater adjusted adult bone geometric measures at the proximal femur than adult participants who were classified as inactive during adolescence (P < 0.05). Skeletal advantages associated with adolescence activity appear to confer greater geometric bone structural strength at the proximal femur in young adulthood.

Does Physical Activity in Adolescence Have Site-Specific and Sex-Specific Benefits on Young Adult Bone Size, Content, and Estimated Strength?

The long-term benefits of habitual physical activity during adolescence on adult bone structure and strength are poorly understood. We investigated whether physically active adolescents had greater bone size, density, content, and estimated bone strength in young adulthood when compared to their peers who were inactive during adolescence. Peripheral quantitative computed tomography (pQCT) was used to measure the tibia and radius of 122 (73 females) participants (age mean ± SD, 29.3 ± 2.3 years) of the Saskatchewan Pediatric Bone Mineral Accrual Study (PBMAS). Total bone area (ToA), cortical density (CoD), cortical area (CoA), cortical content (CoC), and estimated bone strength in torsion (SSIp ) and muscle area (MuA) were measured at the diaphyses (66% tibia and 65% radius). Total density (ToD), trabecular density (TrD), trabecular content (TrC), and estimated bone strength in compression (BSIc ) were measured at the distal ends (4%). Participants were grouped by their adolescent physical activity (PA) levels (inactive, average, and active) based on mean PA Z-scores obtained from serial questionnaire assessments completed during adolescence. We compared adult bone outcomes across adolescent PA groups in each sex using analysis of covariance followed by post hoc pairwise comparisons with Bonferroni adjustments. When adjusted for adult height, MuA, and PA, adult males who were more physically active than their peers in adolescence had 13% greater adjusted torsional bone strength (SSIp , p < 0.05) and 10% greater adjusted ToA (p < 0.05) at the tibia diaphysis. Females who were more active in adolescence had 10% larger adjusted CoA (p < 0.05), 12% greater adjusted CoC (p < 0.05) at the tibia diaphysis, and 3% greater adjusted TrC (p < 0.05) at the distal tibia when compared to their inactive peers. Benefits to tibia bone size, content, and strength in those who were more active during adolescence seemed to persist into young adulthood, with greater ToA and SSIp in males, and greater CoA, CoC, and TrC in females.

Maturational timing does not predict HSA estimated adult bone geometry at the proximal femur

Late maturational timing is documented to be detrimental to bone strength primarily at the distal radius. Studies at the proximal femur have focused on bone mass and the results remain controversial. The purpose of this study was to examine the long term relationship between the onset of maturation and the development of estimated cross sectional area (CSA) and section modulus (Z) at the proximal femur.Two hundred and twenty six individuals (108 males and 118 females) from the Saskatchewan Pediatric Bone Mineral Accrual Study (PBMAS) were classified into maturity groups based on age of attainment of peak height velocity. CSA and Z were serially assessed at the narrow neck (NN), intertrochanter (IT) and proximal shaft (S) sites using hip structural analysis (HSA). Multilevel models were constructed to examine the development of CSA and Z by maturity group.Cross sectional observations indicated that during adolescence, early maturing males had significantly greater CSA and Z than late maturing males at all sites of the proximal femur, while early maturing females had greater Z at the NN and S, and greater CSA at the NN, IT and S sites compared to late maturing females. When age, body size, body composition, physical activity and dietary intake were controlled no significant effects of maturational timing were found at the NN, IT or S regions (p>0.05) in either males or females.In this population of healthy individuals there appears to be no effect of the onset of maturation on estimated CSA and Z development at the proximal femur in both males and females. This may be a result of the proximal femur's loading environment. Future research is required to determine the role of loading on the relationship between maturational timing and bone structure and strength development at the proximal femur.

Relationship Between Trajectories of Trunk Fat Mass Development in Adolescence and Cardiometabolic Risk in Young Adulthood

To examine developmental trajectories of trunk fat mass (FM) growth of individuals categorized as either low or high for cardiometabolic risk at 26 years, a total of 55 males and 76 females from the Saskatchewan Pediatric Bone Mineral Accrual Study (1991-2007) were assessed from adolescence (11.5 ± 1.8 years) to young adulthood (26.2 ± 2.2 years) (median of 11 visits per individual) and had a measure of cardiometabolic risk in young adulthood. Participants were categorized as low or high for blood pressure and cardiometabolic risk as adults using a sex-specific median split of continuous standardized risk scores. Individual trunk FM trajectories of participants in each risk group were analyzed using multilevel random effects models. Males and females in the high blood pressure group had significantly steeper (accelerated) trajectories of trunk FM development (0.61 ± 0.14 and 0.52 ± 0.10log g, respectively) than those in the low blood pressure group for females in the high cardiometabolic risk group trajectory of trunk FM was significantly steeper (0.52 ± 0.10log g) than those females in the low cardiometabolic risk group. Dietary fat was positively related (0.01 ± 0.003g/1,000kcal) and physical activity negatively related (-0.16 ± 0.05 physical activity score) to trunk FM development in males. Young adults with high cardiometabolic risk, compared to low, have greater trunk FM as early as 8 years of age, which supports the need for early intervention.

Does Controlling for Biological Maturity Improve Physical Activity Tracking?

Tracking of physical activity through childhood and adolescence tends to be low. Variation in the timing of biological maturation within youth of the same chronological age (CA) might affect participation in physical activity and may partially explain the low tracking. To examine the stability of physical activity over time from childhood to late adolescence when aligned on CA and biological age (BA). A total of 91 males and 96 females aged 8-15 yr from the Saskatchewan Pediatric Bone Mineral Accrual Study (PBMAS) were assessed annually for 8 yr. BA was calculated as years from age at peak height velocity. Physical activity was assessed using the Physical Activity Questionnaire for Children/Adolescents. Tracking was analyzed using intraclass correlations for both CA and BA (2-yr groupings). To be included in the analysis, an individual required a measure at both time points within an interval; however, not all individuals were present at all tracking intervals. Physical activity tracking by CA 2-yr intervals were, in general, moderate in males (r=0.42-0.59) and females (r=0.43-0.44). However, the 9- to 11-yr CA interval was low and nonsignificant (r=0.23-0.30). Likewise, tracking of physical activity by BA 2-yr intervals was moderate to high in males (r=0.44-0.60) and females (r=0.39-0.62). Accounting for differences in the timing of biological maturity had little effect on tracking physical activity. However, point estimates for tracking are higher in early adolescence in males and to a greater extent in females when aligned by BA versus CA. This suggests that maturity may be more important in physical activity participation in females than males.

Effect of maturational timing on bone mineral content accrual from childhood to adulthood: Evidence from 15 years of longitudinal data

A higher bone mass may reduce the risk of osteoporosis and fractures. The role of maturational timing for optimizing bone mass is controversial due to the lack of prospective evidence from childhood to adulthood. The purpose of this study was to examine the long term relationship between the onset of maturation and bone mineral content (BMC) development. Two hundred thirty individuals (109 males and 121 females) from the Saskatchewan Pediatric Bone Mineral Accrual Study (PBMAS) were classified into maturity groups based on age of peak height velocity. BMC was serially assessed using dual energy X-ray absorptiometry (DXA). Multilevel models were constructed to examine the independent development of BMC by maturity group. When age, body size, and body composition were controlled early maturing females had on average 3–4%, 62.2 ± 16.8 g (p < 0.05), more total body BMC than their average maturing peers by 20 years of age. In contrast, late maturing females had 50.7 ± 15.6 g less total body BMC. No maturational effects were found at either the lumbar spine or femoral neck (p > 0.05) in females. There were no significant differences in BMC development at any site among male maturational groups (p > 0.05). In this group of healthy participants, there appears to be a sex-dependent effect on the relationship between maturational timing and total body BMC development. Early, average and late maturing males displayed similar BMC development. Late maturing females had compromised BMC accrual compared to their early and average maturing peers.

Peak lean tissue mass accrual precedes changes in bone strength indices at the proximal femur during the pubertal growth spurt

Purpose We examined the timing of the age and the magnitude of peak lean tissue mass accrual (PLTV) relative to the age and magnitude of two variables of bone strength [peak cross sectional area velocity (PCSAV), and peak section modulus velocity, (PZV)] at the proximal femur in males and females during the adolescent growth spurt. We hypothesized that the age of PLTV would precede the ages of PCSAV and PZV and that there is a positive relationship between the magnitude of PLTV and both PCSAV and PZV in both genders. Methods 41 males and 42 females aged 8–18 years were selected from the Saskatchewan Pediatric Bone Mineral Accrual Study (1991–2005). Participants' total body lean tissue mass was assessed annually for 6 consecutive years using DXA. Narrow neck and femoral shaft cross sectional areas (CSA) and section modulus ( Z) were determined using the hip structural analysis (HSA) program. Participants were aligned by maturational age (years from peak height velocity). Lean tissue mass, CSA, and Z were converted into whole year velocities and the maturational age of peak tissue velocities was determined using a cubic spline curve fitting procedure. A 2 × 3 (gender × tissue) factorial MANOVA with repeated measures was used to test for differences between age of PLTV and the ages of PCSAV and PZV between genders. Multiple regression analyses were used to examine the relationship between PLTV and both PCSAV and PZV. Results There were no sex differences in the ages at which tissue peaks occurred when aligned by maturational age. There were significant differences between the age of PLTV and both PCSAV and PZV at the narrow neck ( p = 0.001) and femoral shaft ( p = 0.03), where the age of PLTV preceded both PCSAV and PZV when pooled by gender. PLTV was a significant predictor of the magnitude of both PCSAV and PZV at all sites ( p < 0.05). Conclusions These findings support the hypothesis that the age of PLTV precedes the age of PCSA and PZV at the proximal femur. Results support the theory that muscle development is an important factor in affecting bone strength.

A longitudinal study of the relationship of physical activity to bone mineral accrual from adolescence to young adulthood

Physical activity in adolescence is beneficial for increasing bone mineral accrual; however, it's unclear whether these benefits persist into adulthood. This prospective study investigated whether physically active adolescents maintained their higher bone mineral content (BMC) into the third decade of life when compared to their less active peers. Data were from 154 subjects (82 females and 72 males) who participated in the University of Saskatchewan's Pediatric Bone Mineral Accrual Study (1991–1997), entry age 8 to 15 years. Participants returned for follow-up as young adults (2002–2006), follow-up age 23 to 30 years. Dual energy X-ray absorptiometry was used to measure BMC of total body (TB), lumbar spine (LS), total hip (TH) and femoral neck (FN) annually from 1991 to 1997 and from 2002 to 2006. Peak height velocity (PHV) was determined for each child as a measure of maturity. Age and gender-specific activity Z-scores were calculated for each participant based on the mean physical activity scores obtained from bi-annual questionnaire data during childhood and adolescence. Subjects were ranked into three adolescent activity groups: active, average and inactive (top, middle two, and bottom quartiles, respectively). Analysis of covariance (ANCOVA) was used to compare adjusted TB, LS, TH and FN BMC across the three adolescent activity groups at 1 year post PHV and in young adulthood. When compared to the inactive group, active males had 8% greater adjusted BMC at the TB, 13% at the LS and 11% at the TH ( p < 0.05) in adolescence. Active females also had 8% and 15% more adjusted BMC ( p < 0.05) at the TB and LS, respectively, during adolescence. In young adulthood the male and female adolescent active groups were still significantly more active than their peers ( p > 0.05). It was found that active adolescent males had 8–10% more adjusted BMC at the TB, TH and FN ( p < 0.05) in young adulthood and that active adolescent females had 9% and 10% more adjusted BMC at the TH and FN. These results suggest that the skeletal benefits of physically activity in adolescents are maintained into young adulthood.

The influence of physical activity on lean mass accrual during adolescence: a longitudinal analysis

During childhood, physical activity is likely the most important modifiable factor for the development of lean mass. However, the effects of normal growth and maturation must be controlled. To distinguish effects of physical activity from normal growth, longitudinal data are required. One hundred nine boys and one hundred thirteen girls, participating in the Saskatchewan Pediatric Bone Mineral Accrual Study, were repeatedly assessed for 6 yr. Age at entry was 8-15 yr. Stature, body mass, and physical activity were assessed biannually. Body composition was assessed annually by dual-energy X-ray absorptiometry. Physical activity was determined using the physical activity questionnaires for children and adolescence. Biological age was defined as years from age of peak height velocity. Data were analyzed using multilevel random-effects models. In boys, it was found that physical activity had a significant time-dependent effect on lean mass accrual of the total body (484.7+/-157.1 g), arms (69.6+/-27.2 g), legs (197.7+/-60.5 g), and trunk (249.1+/-91.4 g) (P<0.05). Although the physical activity effects were similar in the girls (total body: 306.9+/-96.6 g, arms: 31.4+/-15.5 g, legs: 162.9+/-40.0 g, and trunk: 119.6+/-58.2 g; P<0.05), boys for the same level of activity accrued, depending on the site, between 21 and 120% more absolute lean mass (g). In conclusion, habitual physical activity had a significant independent influence on the growth of lean body mass during adolescence, once biological maturity and stature were controlled.

The Effects of Dietary Protein on Bone Mineral Mass in Young Adults May Be Modulated by Adolescent Calcium Intake ,

The effect of dietary protein on bone mass measures at different life stages is controversial. We investigated the influence of protein intake on bone mass measures in young adults, considering the influence of calcium intake through adolescence. Subjects were 133 young adults (59 males, 74 females) who were participating in the Saskatchewan Pediatric Bone Mineral Accrual Study (1991–1997, 2003–2006). At adulthood, their mean age was 23 y. We assessed dietary intake via serial 24-h recalls carried out at least once yearly. Total body (TB) bone mineral content (BMC) and TB bone mineral density (BMD) were assessed annually using Dual energy X-ray absorptiometry. We determined TB-BMC net gain from the age of peak height velocity (PHV) to early adulthood. We analyzed data from all subjects and subsets based on sex and calcium intake using multiple regression. TB-BMC significantly increased from age at PHV to early adulthood by 41% in males and 37% in females. Height, weight, physical activity, and sex were significant predictors of TB-BMC, TB-BMC net gain, and TB-BMD among all subjects. Protein intake predicted TB-BMC net gain in all subjects (β = 0.11; P = 0.015). In females at peri-adolescence or early adulthood with adequate calcium intake (>1000 mg/d), protein intake positively predicted TB-BMC, TB-BMC net gain, and TB-BMD (P < 0.05). Our results indicate that when calcium intake is adequate, protein intake has a beneficial effect on the bone mass of young adult females. Protein, in the absence of sufficient calcium, does not confer as much benefit to bone.

Do physical maturity and birth date predict talent in male youth ice hockey players?

The aim of this study was to examine the relationships among biological maturity, physical size, relative age (i.e. birth date), and selection into a male Canadian provincial age-banded ice hockey team. In 2003, 619 male ice hockey players aged 14 – 15 years attended Saskatchewan provincial team selection camps, 281 of whom participated in the present study. Data from 93 age-matched controls were obtained from the Saskatchewan Pediatric Bone Mineral Accrual Study (1991 – 1997). During the initial selection camps, birth dates, heights, sitting heights, and body masses were recorded. Age at peak height velocity, an indicator of biological maturity, was determined in the controls and predicted in the ice hockey players. Data were analysed using one-way analysis of variance, logistic regression, and a Kolmogorov-Smirnov test. The ice hockey players selected for the final team were taller, heavier, and more mature (P < 0.05) than both the unselected players and the age-matched controls. Furthermore, age at peak height velocity predicted (P < 0.05) being selected at the first and second selection camps. The birth dates of those players selected for the team were positively skewed, with the majority of those selected being born in the months January to June. In conclusion, team selectors appear to preferentially select early maturing male ice hockey players who have birth dates early in the selection year.