Changes in body composition and bone of female collegiate soccer players through the competitive season and off-season.

OBJECTIVES: To assess body composition and bone changes pre- to post-season (pre-post) and post- to off-season (post-off) in female soccer athletes (SC). METHODS: Outcomes were assessed using DXA and pQCT in 23 SC and 17 controls at three times throughout season. RESULTS: SC, non-starters in particular, lost lean mass pre-post (-0.9±0.2 kg, p<0.01; not different from controls, p=0.2) and gained fat mass post-off (1.4±0.3 kg, p<0.01; differed from controls, p=0.01). Baseline femoral neck and hip aBMD were higher in SC than controls (both,p<0.04), but increased in controls more than SC in pre-post and decreased post-off. SC cortical bone mineral content (BMC), cortical area and periosteal circumference increased pre-post (all, p<0.01; differed from controls, p<0.05) and trabecular vBMD decreased post-off (-3.0±1.3 mg/cm3; p=0.02; not different from controls, p=0.4). Both SC and controls increased cortical BMC, cortical area, and thickness post-off (all, p<0.01). CONCLUSION: Soccer players lost lean mass over the competitive season that was not recovered during off-season. Bone size increased pre- to post-season. Female soccer athletes experience body composition and bone geometry changes that differ depending on the time of season and on athlete's playing status. Evaluations of athletes at key times across the training season are necessary to understand changes that occur.

The negative effect of sitting time on bone is mediated by lean mass in pubertal children.

OBJECTIVE: Effects of time in moderate to vigorous physical activity (MVPA) and sitting (SIT) on bone were tested, hypothesizing that high MVPA would be positively associated with bone size and strength, offset effects of high SIT, and be mediated by lean mass. METHODS: 155 children (79 male, 58 pubertal), 6-20 years (10.2±3.5 yr) were measured by dual-energy x-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT). MVPA and SIT were measured by 7-day activity recall. Regression analyses tested effects of MVPA and SIT on bone. Mediation analysis was conducted to determine if lean mass mediated the effect of activity on bone. RESULTS: In pubertal boys, SIT was negatively associated with tibial endosteal and periosteal circumference as well as bone strength (ß= -0.19, -0.14, and -5.68, respectively; all p<0.05). Effects of SIT on bone circumferences and strength were mediated by lean mass. MVPA did not offset the effects of SIT. In pubertal girls, MVPA was positively associated with cortical thickness (ß=0.01, p<0.05) and the association was not mediated by lean mass. CONCLUSIONS: Current health communications that encourage increased physical activity should include additional messaging to decrease time spent sitting, especially in pubertal boys.

Variation in cortical density within the cortical shell of individuals across a range in densities and ages.

OBJECTIVES: The purpose of this study was to determine variability in cortical volumetric bone density (vBMD) from a single slice tibia image over a range of vBMD readings and ages. METHODS: Males and females (N=80; aged 6-80) were randomly selected from a previous study. Cortical vBMD at the anterior, posterior, medial, and lateral regions as well as the endocortical, mid-cortical, and pericortical regions of the cortical shell were determined using pQCT. RESULTS: Mean anterior ROI cortical vBMD (1111±11 mg/cm(3)) was lower than the posterior and lateral ROIs (1169±7 mg/cm(3) and 1151±9 mg/cm(3), respectively), (p<0.05). Individuals with lower overall cortical vBMD and younger individuals had greater vBMD variability within the shell (r=0.37, p=0.004). Difference between anterior and posterior regions was inversely associated with cortical vBMD and jump power (r=0.46, p=0.001). Endocortical vBMD (1080±6 mg/cm) was lower than the mid-cortical and pericortical regions (1152±5 mg/cm(3) and 1147±5 mg/cm, respectively). CONCLUSIONS: Variability in cortical vBMD was higher among young individuals and those with lower overall cortical vBMD, while lowest in older individuals and men. The anterior ROI had lower mean cortical vBMD than posterior or lateral regions, and endocortical vBMD was lower than the mid- and pericortical regions.

Effect of different collegiate sports on cortical bone in the tibia.

OBJECTIVES: The purpose of this study was to determine the effect of sports participation on cortical bone in the tibia. METHODS: 53 female collegiate athletes (25 cross-country, 16 soccer, and 12 volleyball) and 20 inactive controls had the left distal 20% tibia scanned by pQCT. Cortical volumetric BMD (vBMD) was measured within the cortical shell at the anterior, posterior, medial, and lateral regions and standard deviations were calculated. RESULTS: Total vBMD was greater in the control group (1161±5 mg/mm(3)) than each of the sports (p<0.05). Soccer players (1147±5 mg/mm(3)) had greater vBMD than volleyball players (1136±7 mg/mm(3)) (p<0.05), but similar to cross-country runners (1145±5 mg/mm(3)). Cortical thickness was greatest in soccer players (4.1±0.1 mm), while cross-country and control subjects (3.8±0.1 mm) had greater thickness than volleyball players (3.4±0.1 mm)(p<0.05). Periosteal circumference was greater in volleyball players (71±1.4 mm) than soccer, cross-country, and control subjects (68±0.9, 69±0.8, and 66±1 mm, respectively; all, p<0.05). vBMD variation within the cortical shell was greater among control subjects (70±6 mg/cm(3)) than each of the athlete groups, with soccer players having lower variation than cross country runners (within-in person SD 36±6 mg/cm(3) and 54±5 mg/cm(3) respectively; p<0.05). CONCLUSION: These results indicate bone geometry and distribution within the cortical shell of the tibia varies depending upon sporting activities of young women.

Effect of level of farm mechanization early in life on bone later in life.

OBJECTIVE: To determine whether an active rural lifestyle during childhood and adolescence, defined as low farm mechanization, was associated with bone measures later in life. METHODS: DXA bone data from total body, hip and spine, and pQCT data from 4% and 20% distal radius were obtained on 330 individuals (157 women) aged 20-66 years who farmed at least 75% of their lives. Primary bone outcomes included areal bone mineral density (aBMD), aBMD Z-scores, cortical and trabecular volumetric BMD, cortical thickness and periosteal circumference. Relationship between bone and recall of level of farm mechanization as a child was determined after stratifying by sex and controlling for covariates. RESULTS: Controlling for covariates, females from low mechanized farms had higher femoral neck (FN) bone area (p=0.03) than those on high or moderate mechanized farms. No group differences in pQCT ulna measurements or z-scores were found in either gender. CONCLUSION: A low farm mechanization level (high physical activity) prior to 20 years of age is associated with greater FN bone area in females. Future research that includes type and amount of physical activity performed will contribute to growing knowledge of how and when regular physical activity during childhood and adolescence affects adult bone health.

Determinants of bone mass and size in 7-year-old former term, late-preterm, and preterm boys.

UNLABELLED: When compared, full-term prepubertal boys had greater regional bone size, higher total body (TB) bone mineral content (BMC), and regional bone density than preterm boys but higher TB bone content area and regional BMC than late-preterm boys. Implications include follow-up bone assessment and preterm formula feeding in late-preterm boys. INTRODUCTION: This study was conducted to determine whether there are differences in bone mass and size among prepubertal boys born preterm (PT; < or =34 weeks gestation), late-preterm (LP; >34 and < or =37 weeks gestation), and at term (>37 weeks gestation) and to identify factors that are associated with bone mass and size in these children. METHODS: Total body (TB), spine and hip dual energy X-ray absorptiometry and tibia peripheral quantitative computed tomography measures were obtained on 24 boys aged 5.7 to 8.3 years. RESULTS: In multiple regression analysis adjusting for current weight, height, age, and jump power, term boys had greater cortical thickness (p = 0.03) and area (p = 0.01), higher trabecular volumetric bone mineral density (p = 0.05), TB bone mineral content (BMC; p = 0.007), and hip areal bone mineral density (aBMD; p = 0.01) than PT boys, and higher TB BMC (p = 0.01), TB bone area (p = 0.03), hip BMC (p = 0.02) and aBMD (p = 0.01), and femoral neck BMC (p = 0.05) and aBMD (p = 0.02) than LP boys. There were no differences in activity measures among gestation groups and no group-by-activity interactions. CONCLUSION: Term boys have greater bone size and mass than PT boys and higher bone mass than LP boys at several bone sites. Activity measures did not differ among gestation groups and did not explain bone differences.

Muscle-bone relationships in the lower leg of healthy pre-pubertal females and males.

Muscle-bone relationships in healthy pre-pubertal children were investigated using four muscle measures as predictors of tibial strength: 66% tibia cross-sectional muscle area (CSMA) by pQCT; leg lean mass (LLM) by DXA; and muscle power (Power) and force (Force) measured during a two-footed jump. Polar strength strain index (pSSI), a calculated surrogate for bone strength at the 20% distal tibia, was obtained on 105 (54 male) self-assessed pre-pubertal children. The amount of muscle (CSMA, LLM) may influence bone strength more than muscle strength (Power, Force) during periods of rapid growth. Correlations and multiple regression partial-R values from models controlling for age, sex, height and weight were obtained for each muscle predictor. CSMA, LLM, Power and Force were positively correlated with pSSI (R=0.84, 0.92, 0.85; 0.66, respectively, all p<0.01). Partial-R values were highest for LLM (partial-R=0.21), similar for CSMA and Power (0.14, 0.15, respectively) and lowest for Force (0.04) in predicting pSSI. Muscle predictors were associated with total and cortical area (R=0.59 to 0.90; p<0.01 for all), but not cortical vBMD at the 20% distal tibia site. These data support relationships between muscle predictors and bone parameters measured by pQCT in healthy pre-pubertal children.

Volumetric bone mineral density and bone size in sleep-deprived individuals.

INTRODUCTION: Chronic sleep deprivation, which is associated with several age-related pathologies and altered endocrine function, may adversely affect bone. Our a priori hypothesis was that bone mineral density was lower in sleep-deprived (<6.5 h/night) vs. sleep-adequate (>6.5-10 h/night) individuals. METHODS: Cross-sectional analysis of sleep and bone data on 1,146 individuals (652 women) was performed. Measurements were obtained at the distal radius by pQCT, and the spine and hip by DXA. Bone differences between sleep-deprived and sleep-adequate groups were compared after stratifying by sex and controlling for covariates. RESULTS: Overall, 19% of the population was sleep deprived. Sleep-deprived women had lower cortical volumetric BMD (1,208+/-4 vs. 1,219+/-2 mg/cm(3), P=0.03) than sleep-adequate women. Sleep-deprived men had lower pSSI, an estimate of torsional bending strength, than sleep-adequate men (358+/-10 vs. 382+/-5 mm(3), P=0.04), due to a slightly smaller periosteal circumference (43.9+/-0.4 vs. 44.8+/-0.2 mm, P=0.07) and cortical area (103+/-2 vs. 106+/-1+/-mm(2), P=0.06). CONCLUSION: Sleep deprivation is associated with some, but not all, bone outcomes. These findings may have important public health significance given the increasing prevalence of sleep deprivation.

Influence of rapid growth on skeletal adaptation to exercise.

During rapid growth, increased body weight and muscle strength result in increased loads on bone. Bone adapts to these increased strains by increasing bone modeling and remodeling. As the growth rate decreases, bone that was formed as a result of these adaptations continues to mineralize and "catch up", and bone modeling and remodeling decreases. Bone benefits of exercise in childhood are reported in some studies, although we observed less BMC gain at trabecular-rich sites during the peri-pubertal period in children who jumped than those who did not. Data from 13 existing pediatric exercise studies were compiled to determine whether similar patterns of age-related bone changes could be identified, and whether the bone benefit of exercise differed depending upon pubertal stage. The benefit of exercise on total body BMC gains occurred across all ages, whereas greater exercise-induced gains at the spine and hip were observed in younger children compared to older children. The majority of studies found a positive effect of exercise on bone, but typically this involved limiting the analysis to specific sub-populations (i.e., higher calcium intake, lower baseline activity levels, smaller body size). Limitations of the studies published to date are discussed.

Effect of truncal adiposity on plasma lipid and lipoprotein concentrations.

OBJECTIVE: The purpose of this study was to determine the effect of body fat distribution on plasma lipid and lipoprotein concentrations in healthy individuals. METHODS: Subjects were 290 women and 223 men aged 20-66 years old. Lipid panels were obtained and truncal adiposity measurements were determined by total body dual energy x-ray absorptiometry (DXA). Physical activity was measured using a modification of the Seven Day Physical Activity Recall Questionnaire and dietary intake was collected by 24-hour recall. General linear models were used with covariates included. RESULTS: Percent of total body fat in the trunk had the strongest correlation to the android/gynoid regional fat mass ratio determined by regional DXA analyses in both women (r2=0.97, p < 0.001) and men (r2=0.93, p < 0.001). Total cholesterol (r=0.134, p < 0.05), LDL (r=0.140, p < 0.05), HDL (r= -0.181, p < 0.001), total cholesterol to HDL ratio (r=0.240, p < 0.001) and triglyceride (r=0.300, p < 0.001) concentrations had the strongest correlation to percent of total body fat in the trunk in women. Total cholesterol (r= 0.151, p < 0.05), total cholesterol to HDL ratio (r=0.216, p < 0.001), and triglyceride (r=0.227, p < 0.001) concentrations had the strongest correlation to percent of total body fat located in the trunk among men. CONCLUSION: Lipid profiles, consistent with increased cardiovascular risk, were associated with percent of total body fat in the trunk independent of lifestyle factors.

Bioavailability of vitamin D from fortified process cheese and effects on vitamin D status in the elderly.

We conducted 2 studies to determine the effect of vitamin D-fortified cheese on vitamin D status and the bioavailability of vitamin D in cheese. The first study was designed to determine the effect of 2 mo of daily consumption of vitamin D3-fortified (600 IU/d) process cheese on serum 25-hydroxyvitamin D (25-OHD), parathyroid hormone (PTH), and osteocalcin (OC) concentrations among 100 older (> or =60 yr) men and women. Participants were randomized to receive vitamin D-fortified cheese, nonfortified cheese, or no cheese. Serum levels of 25-OHD, PTH, and OC were measured at the beginning and end of the study. There were no differences in 25-OHD, PTH, or OC after 2 mo of fortified cheese intake. The vitamin D-fortified cheese group had a greater decrease in 25-OHD than other groups, due to higher baseline 25-OHD. A second study was conducted to determine whether the bioavailability of vitamin D2 in cheese (delivering 5880 IU of vitamin D2/56.7-g serving) and water (delivering 32,750 IU/250 mL) is similar and whether absorption differs between younger and older adults. The second study was a crossover trial involving 2 groups of 4 participants each (younger and older group) that received single acute feedings of either vitamin D2-fortified cheese or water. Serial blood measurements were taken over 24 h following the acute feeding. Peak serum vitamin D and area under the curve were similar between younger (23 to 50 yr) and older (72 to 84 yr) adults, and vitamin D2 was absorbed more efficiently from cheese than from water. These studies demonstrated that vitamin D in fortified process cheese is bioavailable, and that young and older adults have similar absorption. Among older individuals, consuming 600 IU of vitamin D3 daily from cheese for 2 mo was insufficient to increase serum 25-OHD during limited sunlight exposure.

Comparison of bone parameters by dual-energy X-ray absorptiometry and peripheral quantitative computed tomography in Hutterite vs. non-Hutterite women aged 35-60 years.

A previous report of elevated dual-energy X-ray absorptiometry (DXA) bone mineral density (BMD) Z scores suggests that Hutterite females might be significantly less likely to develop osteoporosis compared with other U.S. females. In the present study, we sought to determine if high Hutterite DXA BMD Z scores were elevated because of larger bone size. Hutterites reside in isolated, self-sufficient colonies with an emphasis on agricultural production, and girls enter a strenuous task rotation at age 15 years. We obtained cross-sectional bone measurements of the 66% distal tibia using peripheral quantitative computed tomography (pQCT) to compare bone size and geometry on 97 Hutterite and 30 non-Hutterite women, aged 35-60 years. Total body (TB) and lumbar bone mineral content (BMC), BMD, and bone area measurements by DXA were available on a subset of the study population. We identified no differences between groups in pQCT total bone area, cortical bone area, or cortical bone density. Larger bone area by DXA was apparent in Hutterites compared with non-Hutterites at the TB (least square means: 2038 +/- 8 cm2 vs. 1953 +/- 19 cm2, p < 0.05) and lumbar (least square means: 58 +/- 0.5 cm2 vs. 57 +/- 2 cm2, p < 0.01) sites. TB BMC adjusted for TB bone area was marginally higher in Hutterites compared with non-Hutterites (least square means: 2341 +/- 15 g vs. 2281 +/- 30 g, p = 0.08). Hutterites had marginally higher TB BMD Z scores when controlling for weight and age (least square means: 1.3 +/- 0.1 vs. 0.8 +/- 0.2, p = 0.07). Hutterites had higher lumbar BMC adjusted for lumbar bone area and weight (least square means: 65 +/- 1 g vs. 58 +/- 2 g, p < 0.01) and higher weight-and age-adjusted lumbar BMD Z scores (least square means: 1.1 +/- 0.1 vs. 0.1 +/- 0.4, p = 0.01). Our data indicate that a true advantage in trabecular bone density probably exists among Hutterite women aged 35-60 years. Hutterite women might be protected against age-related fractures because of their larger bone size and higher bone density at normally susceptible trabecular sites.

Assessing the body composition of 6-17-year-old Black and White girls in field studies.

The purpose of the study was to develop ethnic-specific equations for fat-free mass (FFM) from selected anthropometric dimensions and bioelectrical impedance measures of resistance (R) and reactance (Xc) for use in the NHLBI Growth and Heath Study. Using dual-energy X-ray absorptiometry measures of body composition as the dependent variable and field measures of body composition by anthropometry and bioelectrical impedance as the explanatory variables, ethnic-specific prediction equations were developed on a sample of girls representing a wide range of ages and BMI. The equations were cross-validated using (1) the Prediction of Sum of Squares (PRESS) statistic and (2) an independent sample of 20 girls of each race from a study conducted at the National Institute of Child Health and Human Development (NICHD). Subjects were 65 White and 61 Black girls 6-17 years of age. The best race-specific equations for FFM each explained 99% and 97% of the variance in the White and Black girls, respectively. Root mean square errors (RMSE) ranged from 1.14 to 1.95 kg. The equation for Black girls used Stature2/Resistance (R), weight, and reactance (Xc) as predictor variables; the equation for White girls used Stature2/R, weight, and triceps skinfold thickness. The results indicate that (1) equations to predict FFM in girls should be ethnic-specific and that (2) accurate values for TBF and %BF can be calculated from the predicted FFM.

Effect of timing of introduction of complementary foods on iron and zinc status of formula fed infants at 12, 24, and 36 months of age.

OBJECTIVE: The timing of introduction of complementary food to an infant's diet is variable throughout the world. Our objective was to determine whether early introduction of complementary foods affects iron and zinc status of formulated infants at 12, 24, and 36 months of age. DESIGN: A randomized, prospective trial was conducted. Infants were randomly assigned to receive either a) early introduction (at 3 to 4 months of age) of commercially prepared or parent's choice of complementary foods; or b) late introduction (at 6 months of age) of commercially prepared complementary foods or parent's choice of complementary foods. In addition to complementary foods, infants were fed commercial infant formula as recommended by their pediatrician. Hemoglobin, mean corpuscular volume, and serum ferritin and zinc concentrations were determined at 12, 24, and 36 months of age. Three-day diet diaries were completed at 3, 6, 12, 18, 24, 30, and 36 months of age. SUBJECTS/SETTING: One hundred seventy-five infants younger than 3 months were recruited by mailings to parents in the Cincinnati area. Of these, 172 were enrolled, 90 in the early-introduction group and 82 in the late-introduction group. One hundred thirty-three infants (n = 67 in the early, n = 66 in the late group) completed the study. STATISTICAL ANALYSES PERFORMED: Student t test and regression analyses were used to determine whether there were group differences and whether there was a relationship between serum parameters and dietary intake. RESULTS: Infants fed complementary foods early had significantly greater iron intakes until 6 months of age; however, there were no differences in the iron status parameters (ferritin, hemoglobin, and mean corpuscular volume) at 12, 24, or 36 months of age. The early introduction group consumed slightly less zinc than the late introduction group at 5 months (4.4 vs 4.8 mg/day, P < .01) and 6 months (4.4 vs 4.7 mg/day, P < .01). At all other times there were no differences between the early and late group in zinc intakes. The serum zinc concentration was not associated with dietary zinc. Both groups had normal serum zinc concentrations at 12, 24, and 36 months and there were no differences between groups. APPLICATIONS/CONCLUSIONS: The iron and zinc status of infants in this study was not influenced by the timing or type of complementary foods introduced. However, the infants were formula fed and the mean iron and zinc intakes that were equal or greater than the Recommended Dietary Allowances for the first 6 months of age.

No differences in growth or body composition from age 12 to 24 months between toddlers consuming 2% milk and toddlers consuming whole milk.

OBJECTIVE: To determine whether consumption of 2% milk during the second year of life leads to reduced growth or lower percentage body fat compared with consumption of whole milk. SUBJECTS: Subjects were healthy toddlers who participated in a larger trial examining the effects of the timing of introduction of solid foods on growth. DESIGN: Three-day diet diaries, anthropometric measurements, and body composition determined by dual-energy x-ray absorptiometry were assessed at 12, 18, and 24 months of age. At age 12 months, the toddlers were similar in length, weight, percentage body fat, and total energy intake. From 12 to 24 months of age, milk consumption consisted of whole milk exclusively in one group (n = 23) and 2% milk exclusively in another group (n = 28). STATISTICAL ANALYSES: Differences between the 2 groups in anthropometric measurements, changes in anthropometric measurements, and dietary intakes were determined by Student t tests. Mean differences were considered significant at the P = .05 level. Data are presented as mean +/- standard deviation. RESULTS: Despite lower intakes of total fat and saturated fat in the 2% milk group, there were no differences in height, weight, and percentage body fat. Total energy intake was not reduced in the 2% milk group. APPLICATIONS: Reductions in total fat and saturated fat intake in toddlers can be achieved through the use of 2% milk without compromising growth.