Knee extension strength in obese and nonobese male adolescents

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

Energy expenditure of severely obese and non-obese adolescents in standardized and free-living conditions

Energy expenditure of severely obese and non-obese adolescents in standardized and free-living conditions. Congrès NAS

Longitudinal changes in activity patterns, physical capacities, energy expenditure, and body composition in severely obese adolescents during a multidisciplinary weight-reduction program

International audienceOBJECTIVE: To determine the longitudinal changes in body composition, physical capacities, and time and energy expenditure (EE) devoted to various activities in the course of a 9-month weight-reduction period. DESIGN: Longitudinal, clinical intervention including lifestyle education, moderate energy restriction, progressive training, and psychological follow-up. SUBJECTS: A total of 27 (13 boys and 14 girls) severely obese adolescents (mean BMI: 33.9 kg/m2; 41.5% fat mass (FM)), aged 12-16 y. MEASUREMENTS: Before the beginning and after the weight-reduction program, body composition was assessed by dual-energy X-ray absorptiometry (DXA), physical capacities by multistage treadmill test, and EE both by whole-body calorimetry and in free-living conditions using the heart rate-recording method. During 8 months of the weight-reduction period, type and duration of each activity were recorded using a daily controlled activity diary. RESULTS: One boy resigned after 5 months. Body weight (BW) and FM decreased (-19 and -42%, respectively, P<0.001) both in boys and in girls, but fat-free mass (FFM) decreased only in girls (-6%, P<0.001). VO2max (l/min) did not vary significantly, but strength and fitness were improved (P<0.001). Time and EE spent at sedentary activities decreased significantly (P<0.001) to the benefit of moderate (recreational) activities and total physical activities (P<0.001) at the institution during the weekdays, and at home during the weekends and holidays. CONCLUSION: The great BW and FM losses, preservation of FFM, and improvement of physical capacities of obese adolescents obtained under experimental conditions were associated with increases in leisure physical activities in free-living conditions at the expense of sleep and sedentary activities

Energy expenditure of severely obese and non-obese adolescents in standardized and free-living conditions.

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Gender effect on exercise-induced energy intake modification among obese adolescents

International audienceThis study examined gender differences in terms of energy intake and appetite feelings after an acute bout of physical exercise among obese adolescents. Seven obese girls and seven obese boys were asked to complete a sedentary and an exercise session in random order, where their food consumption and appetite sensations were assessed. Both boys and girls showed a significant reduction of energy intake on the exercise day without any modification of their appetite readings and no gender differences in food consumption and appetite responses to an acute exercise were noted. (C) 2011 Elsevier Ltd. All rights reserved

Mechanical Work and Metabolic Cost of Walking after Weight Loss in Obese Adolescents

International audiencePurpose: This study was performed to investigate whether changes in biomechanical parameters of walking explain the reduction in net metabolic cost after weight loss in obese adolescents.Methods: Body composition and metabolic and mechanical energy costs of walking at 1.25 m·s(-1) were assessed in 16 obese adolescents before and after a weight loss. Center of mass (COM) and foot accelerations were measured using two inertial sensors and integrated twice to determine COM and foot velocities and displacements. Potential and kinetic energy fluctuations of the COM and the external mechanical work were calculated. Lateral leg swing was calculated from foot displacements.Results: As expected, the decrease in net metabolic cost was greater, which would have been expected on the basis of the amount of weight loss. The smaller lateral leg swing after weight loss did not explain part of the decrease in net metabolic cost. The reduced body mass required less leg muscle work to raise and accelerate the COM as well as to support body weight. The decrease in body mass seems also associated with a lesser leg muscle work required to raise the COM because of smaller vertical motions. As a result of the inverted pendulum mechanism, the decrease in vertical motions (hence in potential energy fluctuations) was probably related to the decrease in mediolateral kinetic energy fluctuations. Moreover, the lesser amount of fat mass in the gynoid region seems related to the decrease in net metabolic cost of walking.Conclusions: The reduction in net metabolic cost of walking after weight loss in weight-reduced adolescents is associated with changes in the biomechanical parameters of walking

Energy expenditure in relation to sex, age, body composition and physical activity in obese and non-obese adolescents

Energy expenditure in relation to sex, age, body composition and physical activity in obese and non-obese adolescents. Réunion du Comité Scientifique International du CRNH d'Auvergne (poster

Study on essential derivation in maize: III. Selection and evaluation of a panel of single nucleotide polymorphism loci for use in European and North American germplasm

Pairwise distance data for maize (Zea mays L.) inbred lines generated using sets of single nucleotide polymorphisms (SNPs) selected from a 50k Infinium array were compared with pairwise distances generated using a set of 163 simple sequence repeat (SSR) loci previously identified to help determine essentially derived variety (EDV) status (UPOV, 1991). Final comparisons were made using 26,874 SNPs after discarding SNPs with insufficient data quality or vulnerability to ascertainment bias. Inbred lines developed in the United States or in western Europe that had been previously published to establish SSR-based thresholds provided the means to determine equivalent SNP-based protocols. Use of 3072 SNPs selected to provide even genomic coverage according to genetic and physical maps provided robust, precise, high discrimination among inbred lines with consistent zonal classification with up to 20% missing data. Comparisons of intercepts and slopes for SSR and SNP inbred pairwise distance data translated the 82% SSR green-orange similarity threshold to 91% using SNPs and the 90% SSR orange-red threshold to 95% using SNPs. Information required to conduct analyses using these 3072 SNPS is presented