Maternal-administered physical activity enhances bone mineral acquisition in premature very low birth weight infants.

OBJECTIVE: To determine if physical activity delivered by an infant's mother would be as effective in promoting bone mineral acquisition in preterm very low birth weight (VLBW) infants as the same intervention administered by a trained therapist. PATIENTS AND METHODS: Preterm VLBW infants were randomized to receive daily physical activity administered by the infant's mother (MOM, n=11) or a trained therapist (OT, n=11), or control (n=11). Physical activity consisted of range of motion movements against passive resistance to all extremities for 5 to 10 min daily. All infants were fed mother's milk with fortification to 24 kcal oz(-1). Dual energy x-ray of the forearm bone area (BA, cm(2)), mineral content (BMC, g), and density (BMD, g/cm(2)) and measurement of bone formation (bone-specific alkaline phosphatase, BAP) and resorption (urine pyridinium crosslinks of collagen, Pyd) were obtained at study entry and at 2.0 kg of body weight. RESULT: Forearm BA and BMC gains were greater in MOM and OT infants compared to the control infants despite similar postnatal growth rate and nutrient intake. Serum BAP levels decreased in controls but remained unchanged in MOM and OT infants. Urine Pyd levels were similar at baseline to 2.0 kg for all groups. These findings suggest greater bone growth and mineral acquisition in MOM and OT infants than control infants. CONCLUSION: This study demonstrates that a physical activity program administered by the infant's own mother is as equally effective as therapist-administered physical activity in promoting greater bone growth and mineral acquisition in preterm VLBW infants.

Interdevice variability in percent fat estimates using the BOD POD.

OBJECTIVE: To evaluate interdevice reliability in body density (Db) and percent body fat (%BF) using air-displacement plethysmography, the BOD POD (BP) body composition system. DESIGN AND SETTING: Duplicate body composition tests were performed in immediate succession on 50 adults (26 M, 24 F; 21-53 y) using two BP units located in the same body composition laboratory. RESULTS: Mean Db and %BF between BP1 and BP2 did not differ significantly for men (DeltaDb = 0.0003+/-0.0008 g/ml, P = 0.632; Delta%BF = 0.1+/-1.3, P = 0.665), while for women, there were small but significant differences in Db and %BF between BP1 and BP2 (DeltaDb = 0.0018+/-0.0003 g/ml, P = 0.001; Delta%BF = 0.8+/-1.1, P = 0.001). The regression between %BF by BP1 and BP2 did not deviate significantly from the line of identity for both men and women (R2 = 0.95, standard error of estimate (s.e.e.) = 1.23 %BF for men; R2 = 0.97, s.e.e = 1.13 %BF for women). Individual variations in %BF estimates between the two BP units were within acceptable ranges (95% limits of agreement = -2.5-2.7 %BF for men; -1.4-3.0 %BF for women), and there was no trend in individual differences as %BF varied (r = -0.19, P = 0.359 for men; r = 0.09, P = 0.677 for women). Other subject characteristics, including age, body mass, height, and body mass index, did not significantly contribute to the differences in %BF estimates by the two BP units. CONCLUSIONS: No clinically significant differences in Db and %BF estimates exist between the BP units, and the interdevice variability of the BP has minimal impact on %BF estimates. Further, test-to-test reliability between BP units appears to be as good as within one unit.

Comparison of anthropometry to DXA: a new prediction equation for men.

OBJECTIVE: This study compared three professionally recommended anthropometric body composition prediction equations for men to dual energy X-ray absorptiometry (DXA), and then developed an updated equation, DXA Criterion (DC) from DXA. DESIGN: Cross-sectional. SETTING: Exercise Physiology Lab. University of Missouri-Columbia, USA. SUBJECTS: A total of 160 men aged 18-62 y old. INTERVENTIONS: Percent body fat (%BF) by anthropometry was compared to DXA on the same day. RESULTS: Although %BF was significantly correlated (r=0.923-0.942) (P<0.01) with DXA for all three equations, each equation underestimated %BF (range=3.1-3.3%) (P<0.01) compared to DXA. The following DC equation for men was created: %BF=0.465+0.180(Sigma7SF)-0.0002406(Sigma7SF)(2)+0.06619(age); (Sigma7SF=sum of chest, midaxillary, triceps, subscapular, abdomen, suprailiac, thigh; age=years). The predicted residual sum of squares (PRESS) R(2) was high (0.90) and the PRESS standard error of estimates was excellent (2.2% at the mean) for the DC equation when applied to our sample of 160 men. CONCLUSIONS: The currently recommended anthropometric equations for men underestimate %BF compared to DXA. The DC equation yields a more accurate estimation of %BF in men aged 18-62 y old. The results from this study support the need for the current %BF standards and norms for men to be adjusted upward.

Bone mass and density response to a 12-month trial of calcium and vitamin D supplement in preadolescent girls.

BACKGROUND: Maximal bone acquisition in adolescent girls through dietary and lifestyle practices is advocated to prevent or minimize the development of osteoporosis and its associated complications in later life. Longitudinal investigations of bone acquisition in children and adolescents have utilized areal bone mineral density (BMD, mg/cm(2)) as a measure of bone mass and strength. Peripheral quantitative computed tomography (pQCT), which provides a three-dimensional display of data, separate analyses of bone compartments, and bone mass in terms of volumetric BMD (vBMD, mg/cm(3)), has recently been introduced for clinical use. OBJECTIVE: To assess the impact of a 12-month daily calcium supplement on total and trabecular bone acquisition as measured by pQCT in preadolescent girls. DESIGN: Early adolescent Caucasian girls (aged 12 years, Tanner Stage 2) were enrolled in a randomized trial of daily calcium supplement (TX, 800 mg calcium carbonate and 400 IU vitamin D) or placebo (C). Body weight, height, and distal tibia measurements by pQCT were obtained at enrollment, 6 and 12 months. Pubertal status and physical activity records were assessed at baseline and 12 months. Three-day food intake records were completed every three months. RESULTS: Seventy-one girls completed the 12-month trial (TX=35, C=36). No differences were found for age, weight, height, body mass index, pubertal maturation, or reported physical activity at enrollment or during the study. Average intakes during the study were 1524 mg calcium and 496 IU vitamin D (TX) versus 865 mg calcium and 160 IU vitamin D (C) per day. Baseline total bone values were similar, however, trabecular values were greater in TX girls despite randomization. Percent changes were calculated to adjust for baseline differences. Because of the small cortical thickness at the 10% site (mean values < 1.6 mm), cortical mass and density were not analyzed. The percent changes for trabecular bone mineral content (BMC, mg) and vBMD were significantly greater in TX girls (+4.1% BMC and +1.0% vBMD TX versus -1.6% BMC and -2.0% vBMD C, p<0.006; ANCOVA) after 12 months of supplement. Trabecular bone area (BA, cm(2)) and total bone change, however, did not differ between groups. CONCLUSIONS: Daily calcium and vitamin D supplementation promotes greater trabecular BMC and vBMD acquisition in preadolescent girls. The single site selected for pQCT evaluation in this study did not allow evaluation of the cortical bone compartment. Future studies that utilize the pQCT technique need to incorporate multiple measurement sites to better assess total, cortical, and trabecular bone.

Effect of exercise timing on postprandial lipemia and HDL cholesterol subfractions.

The purpose of the study was to examine the effect of exercise timing on postprandial lipemia responses. Subjects were 21 recreationally trained men (ages 27 +/- 1.7 yr). Each subject performed four trials: 1) Control (fat meal only), 2) Post (exercise 1 h after a fat meal), 3) 1 h-Pre (exercise 1 h before a fat meal), and 4) 12 h-Pre (exercise 12 h before a fat meal). In each trial, subjects had a standard fat meal to induce postprandial hypertriglyceridemia. Blood samples were taken at 0 h (immediately before the fat meal) and at 2, 4, 6, 8, and 24 h after the meal. In the exercise trials, each subject exercised at 60% of maximal O2 consumption for 1 h. The results indicated that triglyceride area under the curve scores in premeal-exercise trials were lower (P < 0. 05) than those in Post and Control. At 24 h, total high-density lipoprotein (HDL)-cholesterol in the premeal-exercise trials was higher (P < 0.05) than that at 0 h, whereas total HDL-cholesterol was not changed in Control and Post. At 24 h, HDL subtype 2-cholesterol was higher (P < 0.05) in the premeal-exercise trials than in Control, which did not differ from Post. These results suggest that exercising before a fat meal may have a beneficial effect on the triglyceride response and HDL metabolism, which may blunt atherosclerotic process induced by the fat meal.