Search Results

You are looking at 71 - 80 of 253 items for :

  • "dual-energy X-ray absorptiometry" x
Clear All
Restricted access

Linda B. Houtkooper, Veronica A. Mullins, Scott B. Going, C. Harmon Brown and Timothy G. Lohman

This study characterized body composition profiles of elite American heptathletes and cross-validated skinfold (SKF) and bioelectrical impedance analysis (BIA) field method equations for estimation of percent body fat (%Fat) using dual energy x-ray absorptiometry (DXA) as the criterion. Weight, height, fat mass (FM), fat-free mass (FFM), bone mineral density (BMD), and %Fat were measured in 19 heptathletes using standard measurement protocols for DXA, SKFs and BIA. The ages, heights, and weights were respectively 25.5 ± 3.5 years, 175.0 ± 6.6 cm, 67.3 ± 7.1 kg. DXA estimates of mean ± SD values for body composition variables were 57.2 ± 6.1 kg FFM, 10.1 ± 2.6 kg FM, 114 ± 7% BMD for age/racial reference group, and 15 ± 3.0 %Fat. Ranges of bias values for %Fat (DXA minus SKF or BIA) were, respectively, −0.5 to 1.6% and −5.5 to −1.2%. Ranges for standard errors of estimate and total errors were, respectively, SKF 2.4–2.5%, 2.4–2.8% and BIA 3.0%, 5.0–6.5%. Regression analyses of the field methods on DXA were significant (p < .05) for all SKF equations but not BIA equations. This study demonstrates that elite American heptathletes are lean, have high levels of BMD, and that SKF equations provide more accurate estimates of %Fat relative to DXA than estimates from BIA equations.

Restricted access

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.

Restricted access

Thomas B. Walker, Jessica Smith, Monica Herrera, Breck Lebegue, Andrea Pinchak and Joseph Fischer

The purpose of this study was to investigate the ability of whey-protein and leucine supplementation to enhance physical and cognitive performance and body composition. Thirty moderately fit participants completed a modified Air Force fitness test, a computer-based cognition test, and a dual-energy X-ray-absorptiometry scan for body composition before and after supplementing their daily diet for 8 wk with either 19.7 g of whey protein and 6.2 g leucine (WPL) or a calorie-equivalent placebo (P). Bench-press performance increased significantly from Week 1 to Week 8 in the WPL group, whereas the increase in the P group was not significant. Push-up performance increased significantly for WPL, and P showed a nonsignificant increase. Total mass, fat-free mass, and lean body mass all increased significantly in the WPL group but showed no change in the P group. No differences were observed within or between groups for crunches, chin-ups, 3-mile-run time, or cognition. The authors conclude that supplementing with whey protein and leucine may provide an advantage to people whose performance benefits from increased upper body strength and/or lean body mass.

Restricted access

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.

Restricted access

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.

Restricted access

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.

Restricted access

Gary Slater, David Jenkins, Peter Logan, Hamilton Lee, Matthew Vukovich, John A. Rathmacher and Allan G. Hahn

This investigation evaluated the effects of oral β-Hydroxy-β-Methylbutyrate (HMB) supplementation on training responses in resistance-trained male athletes who were randomly administered HMB in standard encapsulation (SH), HMB in time release capsule (TRH), or placebo (P) in a double-blind fashion. Subjects ingested 3 g · day−1 of HMB or placebo for 6 weeks. Tests were conducted pre-supplementation and following 3 and 6 weeks of supplementation. The testing battery assessed body mass, body composition (using dual energy x-ray absorptiometry), and 3-repetition maximum isoinertial strength, plus biochemical parameters, including markers of muscle damage and muscle protein turnover. While the training and dietary intervention of the investigation resulted in significant strength gains (p < .001) and an increase in total lean mass (p = .01), HMB administration had no influence on these variables. Likewise, biochemical markers of muscle protein turnover and muscle damage were also unaffected by HMB supplementation. The data indicate that 6 weeks of HMB supplementation in either SH or TRH form does not influence changes in strength and body composition in response to resistance training in strength-trained athletes.

Restricted access

Herculina S. Kruger, Lize Havemann-Nel, Chrisna Ravyse, Sarah J. Moss and Michael Tieland

Background:

Black women are believed to be genetically less predisposed to age-related sarcopenia. The objective of this study was to investigate lifestyle factors associated with sarcopenia in black South African (SA) urban women.

Methods:

In a cross-sectional study, 247 women (mean age 57 y) were randomly selected. Anthropometric and sociodemographic variables, dietary intakes, and physical activity were measured. Activity was also measured by combined accelerometery/heart rate monitoring (ActiHeart), and HIV status was tested. Dual energy x-ray absorptiometry was used to measure appendicular skeletal mass (ASM). Sarcopenia was defined according to a recently derived SA cutpoint of ASM index (ASM/height squared) < 4.94 kg/m2.

Results:

In total, 8.9% of the women were sarcopenic, decreasing to 8.1% after exclusion of participants who were HIV positive. In multiple regressions with ASM index, grip strength, and gait speed, respectively, as dependent variables, only activity energy expenditure (β = .27) was significantly associated with ASM index. Age (β = –.50) and activity energy expenditure (β = .17) were significantly associated with gait speed. Age (β = –.11) and lean mass (β = .21) were significantly associated with handgrip strength.

Conclusions:

Sarcopenia was prevalent among these SA women and was associated with low physical activity energy expenditure.

Restricted access

Michael J. Davies, Gail P. Dalsky and Paul M. Vanderburgh

This study employed allometry to scale maximal oxygen uptake (V̇O2 max) by body mass (BM) and lean body mass (LBM) in healthy older men. Ratio standards (ml · kg−1 · min−1) derived by dividing absolute V̇O2 max (L · min−1) by BM or LBM often fail to control for the body size variable. The subjects were 73 older men (mean ± SD: age = 69.7 ± 4.3 yrs, BM = 80.2 ± 9.6 kg, height = 174.1 ± 6.9 cm). V̇O2 max was assessed on a treadmill with the modified Balke protocol (V̇O2 max = 2.2 ± 0.4 L · min−1). Body fat (27.7 ± 6.4%) was assessed with dual energy x-ray absorptiometry. Allometry applied to BM and V̇O2 max determined the BM exponent to be 0.43, suggesting that heavier older men are being penalized when ratio standards are used. Allometric scaling applied to LBM revealed the LBM exponent to be 1.05 (not different from the ratio standard exponent of 1.0). These data suggest that the use of ratio standards to evaluate aerobic fitness in older men penalized fatter older men but not those with higher LBM.

Restricted access

Gladys Block, Christopher D. Jensen, Torin J. Block, Jean Norris, Tapashi B. Dalvi and Ellen B. Fung

Background:

Understanding and increasing physical activity requires assessment of occupational, home, leisure and sedentary activities.

Methods:

A physical activity questionnaire was developed using data from a large representative U.S. sample; includes occupational, leisure and home-based domains; and produces estimates of energy expenditure, percent body fat, minutes in various domains, and meeting recommendations. It was tested in 396 persons, mean age 44 years. Estimates were evaluated in relation to percent body fat measured by dual-energy x-ray absorptiometry.

Results:

Median energy expenditure was 2,365 kcal (women) and 2,960 kcal (men). Women spent 35.1 minutes/day in moderate household activities, 13.0 minutes in moderate leisure and 4.0 minutes in vigorous activities. Men spent 18.0, 22.5 and 15.6 minutes/day in those activities, respectively. Men and women spent 276.4 and 257.0 minutes/day in sedentary activities. Respondents who met recommendations through vigorous activities had significantly lower percent body fat than those who did not, while meeting recommendations only through moderate activities was not associated with percent body fat. Predicted and observed percent body fat correlated at r = .73 and r = .82 for men and women respectively, P < .0001.

Conclusions:

This questionnaire may be useful for understanding health effects of different components of activity, and for interventions to increase activity levels.