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Jeanne F. Nichols, Karen P. Nelson, Katrina K. Peterson and David J. Sartoris

The purpose of this investigation was to determine the effects of high-intensity strength training on bone mineral density (BMD) of 34 non-estrogen-repleted, active women over 60 years of age. The study was designed as a randomized, nonblinded trial in which subjects were stratified into rank-ordered pairs by level of physical activity, then randomly assigned into either a weight training (WT) or a control (CON) group. BMD of the spine (L2–L4), hip, and total body was assessed at 0, 6, and 12 months by dual energy x-ray absorptiometry. Group-by-time repeated-measures ANOVA demonstrated no effect of weight training on BMD, despite marked gains in muscular strength for all exercises. The high-intensity weight training utilized in this study did not induce positive changes in BMD of the hip and spine of previously active, non-estrogen-repleted older women. However, the protocol was safe, enjoyable, and highly effective in increasing muscular strength.

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Élvio R. Gouveia, Bruna R. Gouveia, José A. Maia, Cameron. J. Blimkie and Duarte L. Freitas

The aims of this study were to describe age- and sex-related differences in total body skeletal muscle (TB-SM) mass and to determine the variance explained by physical activity (PA). This cross-sectional study included 401 males and 402 females, aged 60–79 years. TB-SM was determined by dual-energy x-ray absorptiometry (DXA) and PA by Baecke questionnaire. Statistical analysis included t test, ANOVAs, Pearson correlations, and multiple regression analysis. TB-SM mass was higher in the youngest age group when compared with the oldest in males and females. Males had greater TB-SM values than females. PA made a significant and positive contribution to the variation in TB-SM, β = 0.071; p = .016. Sex, height, fat mass, and PA explained 77% of the variance in TB-SM. The oldest cohorts and females had lower TB-SM than the younger cohorts and males. This study suggests that PA exerts a significant role in the explanation of TB-SM.

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Richard B. Kreider, Robert Klesges, Karen Harmon, Pamela Grindstaff, Leigh Ramsey, Daryll Bullen, Larry Wood, Yuhua Li and Anthony Almada

This study examined the effects of ingesting nutritional supplements designed to promote lean tissue accretion on body composition alterations during resistance training. Twenty-eight resistance-trained males blindly supplemented their diets with maltodextrin (M), Gainers Fuel® 1000 (GF), or Phosphagain™ (P). No significant differences were observed in absolute or relative total body water among groups. Energy intake and body weight significantly increased in all groups combined throughout the study with no group or interaction differences observed. Dual energy x-ray absorptiometry-determined body mass significantly increased in each group throughout the study with significantly greater gains observed in the GF and P groups. Lean tissue mass (excluding bone) gain was significantly greater in the P group, while fat mass and percent body fat were significantly increased in the GF group. Results indicate that total body weight significantly increased in each group and that P supplementation resulted in significantly greater gains in lean tissue mass during resistance training.

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Ann V. Rowlands, Sarah M. Powell, Roger G. Eston and David K. Ingledew

This study aimed to determine the relationship between bone mineral content, habitual physical activity, and calcium intake in children. Fifty-seven children, aged 8–11 years, wore pedometers for seven days to assess activity. Calcium intake was estimated by a 4-day food diary. Bone mineral content (BMC) and areal density (BMD) were measured at the total proximal femur and femoral neck using dual energy X-ray absorptiometry. Regression analysis was used to assess contributions of physical activity and calcium intake to BMC, residualized for bone area and body mass. Physical activity explained 11.6% of the variance in residualized BMC at the proximal femur and 14.3% at the femoral neck (p < 0.05). Calcium intake added to the variance explained at the proximal femur only (9.8%, p < 0.05). This study provides evidence for an association between BMC and habitual physical activity.

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Saori I. Braun, Youngdeok Kim, Amy E. Jetton, Minsoo Kang and Don W. Morgan

The purpose of this study was to determine if bone health at the femoral neck (FN) and lumbar spine (LS) can be predicted from objectively-measured sedentary behavior and physical activity data in postmenopausal women. Waist-mounted ActiGraph GT1M and GT3X devices were used to quantify levels of sedentary and moderate-to-vigorous intensity behavior during a 7-day period in 44 older females. Bone health (normal and osteopenia/osteoporosis) of FN and LS was derived from T scores generated using dual energy x-ray absorptiometry. Binomial logistic regression analysis indicated that sedentary time and number of breaks in sedentary behavior were significant predictors of osteopenia/osteoporosis at the FN, but not at the LS. Adherence to physical activity guidelines was not a significant predictor of bone health at the FN or LS. Our findings suggest that more frequent interruptions in sedentary behavior are associated with improved bone health in postmenopausal women.

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Soyang Kwon, Kathleen F. Janz, Trudy L. Burns and Steven M. Levy

The purpose of this study was to examine whether the association between daily light-intensity physical activity (LPA) and total body fat mass changes during childhood. The study sample was 577 children participating in the longitudinal Iowa Bone Development Study. Body fat mass and physical activity (PA) were measured using dual energy X-ray absorptiometry (DXA) and accelerometers, respectively, at approximately 5, 8, and 11 years of age. Age- and gender-specific multivariable linear regression models were fit to predict fat mass by LPA, adjusted for actual age, birth weight, fat-free mass, height, moderate- to vigorous-intensity PA, and physical maturity (only for girls). Among boys, LPA was negatively associated with fat mass at age 11, but not age 5 or 8. Among girls, LPA was negatively associated with fat mass at ages 8 and 11, but not at age 5. LPA may have a beneficial effect against excess adiposity among older children.

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Joyce E. Ballard, Lorraine S. Wallace, David B. Holiday, Cassandra Herron, Liberty L. Harrington, Karen C. Mobbs and Patricia Cussen

This study assessed differences in bone-mineral density (BMD) and lean and fat tissues between 5 age groups of White men age 65–93 years. Lean and fat tissues were measured with absorptiometry and anthropometry, and BMD, with dual-energy X-ray absorptiometry. Forearm, spinal, and femoral T scores were used to classify BMD as normal, osteopenic, or osteoporotic. A questionnaire evaluated previous physical activity, calcium intake, and bone fractures. Significantly lower values in body weight, lean tissue, and forearm BMD occurred in the older age groups. Significant, positive relationships were found between total lean tissue and radial, spinal, and hip BMDs. For the total group, osteopenic and osteoporotic T scores, respectively, were femoral neck 70.6% and 9.8%, radius 27.5% and 25.5%, and spine 25.5% and 7.8%. Differences in BMD values were found between levels of lifestyle factors (dietary calcium and history of previous fractures). In conclusion, elderly men should be encouraged to maintain adequate total lean tissue because of its association with BMD.

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Jason Wicke and Genevieve A. Dumas

Body segment inertial parameters are required as input parameters when the kinetics of human motion is to be analyzed. However, owing to interindividual differences in body composition, noninvasive inertial estimates are problematic. Dual-energy x-ray absorptiometry (DXA) is a relatively new imaging approach that can provide cost- and time-effective means for estimating these parameters with minimal exposure to radiation. With the introduction of a new generation of DXA machines, utilizing a fan-beam configuration, this study examined their accuracy as well as a new interpolative data-reduction process for estimating inertial parameters. Specifically, the inertial estimates of two objects (an ultra-high molecular density plastic rod and an animal specimen) and 50 participants were obtained. Results showed that the fan-beam DXA, along with the new interpolative data-reduction process, provided highly accurate estimates (0.10–0.39%). A greater variance was observed in the center of mass location and moment of inertia estimates, likely as a result of the course end-point location (1.31 cm). However, using a midpoint interpolation of the end-point locations, errors in the estimates were greatly reduced for the center of mass location (0.64–0.92%) and moments of inertia (–0.23 to –0.48%).

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Melissa Hodge, Mary Hovinga, Kelley Gabriel, Linda Snetselaar, John Shepherd, Linda Van Horn, Victor Stevens, Brian Egleston, Alan Robson, Seungyoun Jung and Joanne Dorgan

This study prospectively investigates associations between youth moderate-to-vigorous-intensity physical activity (MVPA) and body composition in young adult women using data from the Dietary Intervention Study in Children (DISC) and the DISC06 Follow-Up Study. MVPA was assessed by questionnaire on 5 occasions between the ages 8 and 18 years and at age 25-29 years in 215 DISC female participants. Using whole body dual-energy x-ray absorptiometry (DXA), overall adiposity and body fat distribution were assessed at age 25-29 years by percent body fat (%fat) and android-to-gynoid (A:G) fat ratio, respectively. Linear mixed effects models and generalized linear latent and mixed models were used to assess associations of youth MVPA with both outcomes. Young adult MVPA, adjusted for other young adult characteristics, was significantly inversely associated with young adult %fat (%fat decreased from 37.4% in the lowest MVPA quartile to 32.8% in the highest (p-trend = 0.02)). Adjusted for youth and young adult characteristics including young adult MVPA, youth MVPA also was significantly inversely associated with young adult %fat (β=-0.40 per 10 MET-hrs/wk, p = .02) . No significant associations between MVPA and A:G fat ratio were observed. Results suggest that youth and young adult MVPA are important independent predictors of adiposity in young women.

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Ann M. Swartz, Sergey Tarima, Nora E. Miller, Teresa L. Hart, Elizabeth K. Grimm, Aubrianne E. Rote and Scott J. Strath

The purpose of the study was to determine the relationship between sedentary behavior (SB), physical activity (PA), and body fat (total, abdominal) or body size (body-mass index [BMI], waist circumference [WC]) in community-dwelling adults 50 yr old and over. This study included 232 ambulatory adults (50–87 yr, 37.4% ± 9.6% body fat [BF]). Average daily time spent in SB (<100 counts/min) and light (100–759 counts/min), lifestyle-moderate (760–1,951 counts/min), walking-moderate (1,952–5,724cts/min), and vigorous-intensity (≥5,725 counts/min) PA were determined by accelerometer and corrected for wear time. BF was measured with dual-energy X-ray absorptiometry. SB was positively related to measures of BF. Measures of SB, PA, and gender accounted for 55.6% of the variance in total BF, 32.4% of the variance in abdominal fat, and 28.0% of the variance in WC. SB, PA, and age accounted for 27.1% of the variance in BMI. Time spent in SB should be considered when designing obesity interventions for adults 50 yr old and over.