Abdominal fat assessment in adolescents using dual-energy X-ray absorptiometry.
ABSTRACT Abdominal obesity is an increasing problem in adolescents, often persisting into adulthood. Reliable assessment has been restricted to techniques limited by relatively high radiation doses or cost.
To investigate the reliability of several abdominal regions using dual-energy X-ray absorptiometry (DXA), and to assess the construct validity of these methods against metabolic profile.
Inter- and intra-rater precision of two assessors were examined, for fat mass analysis in six different abdominal regions using DXA in overweight/obese and normal weight adolescents. Construct validity was examined in overweight/obese individuals.
All methods had acceptable intra- and inter-rater reliability. Region 1 was most precise in overweight/obese individuals, while Region 6 was most precise in normal weight individuals. In all regions, assessments were less precise in overweight/obese individuals. All regions were equally predictive of insulin outcomes.
Abdominal adiposity can be reliably assessed in adolescents using DXA, and the most precisely assessed regions were identified. All regions predicted insulin outcomes.
Full-textDOI: · Available from: Tracey W Tsang, Jul 06, 2015
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ABSTRACT: The aim of the present study was to compare "absolute" and "relative" knee extension strength between obese and nonobese adolescents. Ten nonobese and 12 severely obese adolescent boys of similar chronological age, maturity status, and height were compared. Total body and regional soft tissue composition were determined using dual-energy X-ray absorptiometry (DXA). Knee extensors maximum voluntary contraction (MVC) torque was measured using an isometric dynamometer at a knee angle of 60° (0° is full extension). Absolute MVC torque was significantly higher in obese adolescents than in controls. However, although MVC torque expressed per unit of body mass was found to be significantly lower in obese adolescent boys, no significant difference in MVC torque was found between groups when normalized to fat-free mass. Conversely, when correcting for thigh lean mass and estimated thigh muscle mass, MVC torque was significantly higher in the obese group (17.9% and 22.2%, respectively; P <0.05). To conclude, our sample of obese adolescent boys had higher absolute and relative knee extension strength than our nonobese controls. However, further studies are required to ascertain whether or not relative strength, measured with more accurate in vivo methods such as magnetic resonance imaging, is higher in obese adolescents than in nonobese controls.Applied Physiology Nutrition and Metabolism 03/2012; 37(2):269-75. DOI:10.1139/h2012-010 · 2.23 Impact Factor
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ABSTRACT: Aim. To examine the efficacy of a six-month Kung Fu (KF) program on physical fitness in overweight/obese adolescents. Methods. Subjects were randomly assigned to the KF or sham exercise (Tai Chi, TC) control group. Physical measurements in cardiovascular fitness and muscle fitness occurred at baseline and after 6 months of training thrice weekly. Results. Twenty subjects were recruited. One subject was lost to follow-up, although overall compliance to the training sessions was 46.7 +/- 27.8%. At follow-up, the cohort improved in absolute upper (P = .002) and lower (P = .04) body strength, and upper body muscle endurance (P = .02), without group differences. KF training resulted in significantly greater improvements in submaximal cardiovascular fitness (P = .03), lower body muscle endurance (P = .28; significant 95% CI: 0.37-2.49), and upper body muscle velocity (P = .03) relative to TC training. Conclusions. This short-term KF program improved submaximal cardiovascular fitness, lower body muscle endurance, and muscle velocity, in overweight/obese adolescents with very low baseline fitness.Journal of obesity 01/2010; 2010(2090-0708). DOI:10.1155/2010/672751
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ABSTRACT: Body composition is well known to be associated with endurance performance among adult skiers; however, the association among adolescent crosscountry and alpine skiers is inadequately explored. The study sample comprised 145 male and female adolescent subjects (aged 15-17 years), including 48 crosscountry skiers, 33 alpine skiers, and 68 control subjects. Body composition (%body fat [BF], %lean mass [LM], bone mineral density [grams per centimeter squared]) was measured with a dual-emission x-ray absorptiometer, and pulse and oxygen uptake was measured at 3 break points during incremental performance tests to determine physical fitness levels. Female crosscountry and alpine skiers were found to have significantly higher %LM (mean difference = 7.7%, p < 0.001) and lower %BF (mean difference = 8.1%, p < 0.001) than did female control subjects. Male crosscountry skiers were found to have lower %BF (mean difference = 3.2%, p < 0.05) and higher %LM (mean difference = 3.3%, p < 0.01) than did male alpine skiers and higher %LM (mean difference = 3.7%, p < 0.05) and %BF (mean difference = 3.2%, p < 0.05) than did controls. This study found strong associations between %LM and the onset of blood lactate accumulation and VO2max weight adjusted thresholds among both genders of the crosscountry skiing cohort (r = 0.47-0.67, p < 0.05) and the female alpine-skiing cohort (r = 0.77-0.79, p < 0.001 for all). This study suggests that body composition is associated with physical performance amongst adolescents.The Journal of Strength and Conditioning Research 07/2012; 26(7):1799-804. DOI:10.1519/JSC.0b013e318237e8da · 1.86 Impact Factor