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Christie L. Ward, Rudy J. Valentine and Ellen M. Evans

Adiposity, lean mass, and physical activity (PA) are known to influence physical function in older adults, although the independent influences are not completely characterized. Older adults (N = 156, M age = 68.9 ± 6.7 yr, 85 men) were assessed for body composition via dual-energy X-ray absorptiometry, PA by accelerometer, and physical function via timed up-and-go (UP&GO), 30-s chair stand, 6-min walk (6-min WALK), and Star-Excursion Balance Test. In the absence of percentage-body-fat by PA interactions (p > .05), main effects existed such that a higher percentage body fat was associated with poorer performance in UP&GO, 30-s chair stand, and 6-min WALK (p < .05). No significant main effects were found for PA and functional performance. Adiposity explains 4.6–11.4% in physical functional variance (p < .05). Preventing increases in adiposity with age may help older adults maintain functional independence.

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Jennifer Gornall and Rudolph G. Villani

The primary aim was to investigate whether the reduction in resting metabolic rate (RMR) and fat free mass (FFM) associated with a short-term very low kilojoule diet (VLKD) is altered by concurrent resistance exercise. Twenty overweight, premenopausal women were pair matched on body surface area and randomly assigned to either diet only (3,400 kJ/day) or diet combined with resistance training. Before and after 4 weeks of treatment, RMR was assessed by indirect calorimetry; total body mass (TBM), FFM, and fat mass (FM) by dual energy x-ray absorptiometry; total body water (TBW) by bioelectrical impedance; and strength by a weight-lifting test. Both groups had significantly lower TBM, FFM, FM, TBW, absolute RMR, and RMR, with FFM as the covariate, in the posttests than the pretests with no significant differences between groups. It was concluded that 4 weeks of resistance training did not prevent or reduce the decline in FFM and RMR observed with a VLKD.

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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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Peter N. Wiebe, Cameron J.R. Blimkie, Nathalie Farpour-Lambert, Julie Briody, Helen Woodhead, Chris Cowell and Robert Howman-Giles

The correlates and determinants of total body (TB), femoral neck (FN), greater trochanter (GT) and leg areal bone mineral density (aBMD), and FN volumetric (vol) BMD were investigated in 42 healthy 6–10-year-old girls. Predictor variables included age, height, weight, lean tissue mass (LTM), fat mass, percent body fat, physical activity level, calcium intake, isokinetic knee flexion and extension strength and endocrine (E2) status. Bone density and body composition were determined by dual energy-x-ray absorptiometry (DEXA), and pubertal status was self-determined. LTM, weight, age, knee extensor strength and fat mass were significantly correlated (Pearson correlation coefficients; 0.36 £ r ‡ 0.62) with TBaBMD. These same variables with the addition of height and knee flexor strength were significantly correlated (0.33 £ r ‡ 0.77) with leg aBMD. Only LTM correlated significantly with FNaBMD and none of the independent variables correlated with FNvolBMD or GTaBMD. Only LTM entered as a significant predictor in multiple linear regression analysis (R 2 = 46.7%) for TBaBMD. In conclusion, estradiol status, dietary calcium intake and physical activity level appeared not to be important predictors of BMD in this population, whereas LTM was consistently correlated with most BMD measures and was the single significant determinant of TBaBMD in this study.

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Peter N. Wiebe, Cameron J. R. Blimkie, Nathalie Farpour-Lambert, Julie Briody, Damian Marsh, Allan Kemp, Chris Cowell and Robert Howman-Giles

Few studies have explored osteogenic potential of prepubertal populations. We conducted a 28-week school-based exercise trial of single-leg drop-landing exercise with 42 prepubertal girls (6 to 10 yrs) randomly assigned to control (C), low-drop (LD) or high-drop (HD) exercise groups. The latter two groups performed single-leg drop-landings (3 sessions/wk−1 and 50 landings/session−1) from 14cm(LD) and 28cm(HD) using the nondominant leg. Osteogenic responses were assessed using Dual Energy X-ray Absorptiometry (DXA). Single-leg peak ground-reaction impact forces (PGRIF) in a subsample ranged from 2.5 to 4.4 × body-weight (BW). No differences (p > .05) were observed among groups at baseline for age, stature, lean tissue mass (LTM), leisure time physical activity, or average daily calcium intake. After adjusting for covariates of body mass, fat mass and LTM, no differences were found in bone mineral measures or site-specific bone mineral density (BMD) at the hip and lower leg among exercise or control groups. Combining data from both exercise groups failed to produce differences in bone properties when compared with the control group. No changes were apparent for between-leg differences from baseline to posttraining. In contrast to some reports, our findings suggest that strictly controlled unimodal, unidirectional single-leg drop-landing exercises involving low-moderate peak ground-reaction impact forces are not osteogenic in the developing prepubertal female skeleton.

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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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Ann L. Gibson, Vivian H. Heyward, Christine M. Mermier, Jeffrey M. Janot and M. Virginia Wilmerding

The authors used 3-component (3C) Db-mineral-model (Lohman, 1986) reference measures to cross-validate Siri’s (1961) 2-component (2C) conversion formula and dual-energy X-ray absorptiometry (DXA) estimates of relative body fat (%BF) for physically active adults. Participants varied in age (18 to 59 y), body fatness, ethnicity (black, Hispanic, white), and physical activity level. The 3C Db-mineral model was used to obtain reference measures of %BF (%BF3C) for comparison with body-composition measures from DXA and hydrodensitometry. For men (n = 110) and women (n = 110), %BF3C (14.0% BF and 24.4% BF, respectively) was more accurately estimated by Siri’s 2C formula (%BFSiri; men, r = 0.97, SEE = 1.77% BF; women, r = 0.98, SEE = 1.56% BF) than by DXA (%BFDXA; men, r = 0.86, SEE = 3.54% BF; women, r = 0.88, SEE = 3.73% BF). The average %BFSiri (men, 15.8% BF; women, 24.7% BF) and %BFDXA (men, 16.2% BF; women, 26.0% BF) differed significantly (P < 0.001) from %BF3C. Siri’s 2C model estimated the average %BF3C in this sample more accurately than DXA did.

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Michael R. Esco, Brett S. Nickerson, Sara C. Bicard, Angela R. Russell and Phillip A. Bishop

The purpose of this investigation was to evaluate measurements of body-fat percentage (BF%) in 4 body-mass-index- (BMI) -based equations and dual-energy X-ray absorptiometry (DXA) in individuals with Down syndrome (DS). Ten male and 10 female adults with DS volunteered for this study. Four regression equations for estimating BF% based on BMI previously developed by Deurenberg et al. (DEBMI-BF%), Gallagher et al. (GABMI-BF%), Womersley & Durnin (WOBMI-BF%), and Jackson et al. (JABMI-BF%) were compared with DXA. There was no significant difference (p = .659) in mean BF% values between JABMI-BF% (BF% = 40.80% ± 6.3%) and DXA (39.90% ± 11.1%), while DEBMI-BF% (34.40% ± 9.0%), WOBMI-BF% (35.10% ± 9.4%), and GABMI-BF% (35.10% ± 9.4%) were significantly (p < .001) lower. The limits of agreement (1.96 SD of the constant error) varied from 9.80% to 16.20%. Therefore, BMI-based BF% equations should not be used in individuals with DS.

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Hawley Chase Almstedt and Zakkoyya H. Lewis

Context:

Intermittent pneumatic compression (IPC) is a common therapeutic modality used to reduce swelling after trauma and prevent thrombosis due to postsurgical immobilization. Limited evidence suggests that IPC may decrease the time needed to rehabilitate skeletal fractures and increase bone remodeling.

Objective:

To establish feasibility and explore the novel use of a common therapeutic modality, IPC, on bone mineral density (BMD) at the hip of noninjured volunteers.

Design:

Within-subjects intervention.

Setting:

University research laboratory.

Participants:

Noninjured participants (3 male, 6 female) completed IPC treatment on 1 leg 1 h/d, 5 d/wk for 10 wk. Pressure was set to 60 mm Hg when using the PresSsion and Flowtron Hydroven compression units.

Main Outcome Measures:

Dual-energy X-ray absorptiometry was used to assess BMD of the hip in treated and nontreated legs before and after the intervention. Anthropometrics, regular physical activity, and nutrient intake were also assessed.

Results:

The average number of completed intervention sessions was 43.4 (± 3.8) at an average duration of 9.6 (± 0.8) wk. Repeated-measures analysis of variance indicated a significant time-by-treatment effect at the femoral neck (P = .023), trochanter (P = .027), and total hip (P = .008). On average, the treated hip increased 0.5–1.0%, while the nontreated hip displayed a 0.7–1.9% decrease, depending on the bone site.

Conclusion:

Results of this exploratory investigation suggest that IPC is a therapeutic modality that is safe and feasible for further investigation on its novel use in optimizing bone health.

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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.