Showing papers by "Claude Bouchard published in 1991"

Growth, Maturation, and Physical Activity

Abstract: Introducing the Basics of Growth, Maturation, and Performance Age- and Sex-Associated Variation in Growth Age- and Sex-Associated Variation in Performance Biological Maturation Regulatory and Influencing Factors The Child in Physical Activity and Sport: Applications

Exercise, fitness, and health : a consensus of current knowledge

Abstract: Part I: Consensus Statement and Introductory Addresses. Part II: Assessment and Determinants of Physical Activity, Fitness, and Health. Part III: Human Adaptation to Physical Activity. Part IV: Physical Activity and Fitness in Disease. Part V: Physical Activity and Fitness in Growth, Reproductive Health, and Ageing. Part VI: The Risks of Exercising.

Current understanding of the etiology of obesity: genetic and nongenetic

Abstract: Four types of human obesities are defined by topography of fat deposition. The focus of the paper is on the genetic determinants and the nongenetic correlates of the first type, which is commonly defined as excess weight-for-height or excess body fat without a particular concentration of fat in a given area of the body. The heritability of fat mass or percent body fat derived from underwater-weighing assessment of body density reaches '�-25% of the age- and gender-adjusted pheno- typic variance. The within-identical-twin-pair resemblance in the response to a standardized overfeeding protocol emphasizes the importance of the genotype in determining individual dif- ferences in body weight and body composition. In this regard, the proneness to store energy primarily as fat or as lean tissue is a major determinant of the response to a caloric sur- plus. Am J C/in Nutr 199l;53:l56lS-5S.

Mitochondrial DNA sequence polymorphism, VO2max, and response to endurance training.

Abstract: DIONNE, F. T., L. TURCOTTE, M.-C., THIBAULT, M. R. BOULAY, J. S. SKINNER, and C. BOUCHARD. Mitochondrial DNA sequence polymorphism, VO2max, and response to endurance training. Med. Sci. Sports Exerc., Vol. 23, No. 2, pp. 177–185, 1991. Mitochondrial DNA sequence variation was determined in 4

Normalization of the metabolic profile in obese women by exercise and a low fat diet.

Abstract: This study was performed to evaluate the additive effect of exercise and a low fat diet on body weight, body composition, and the metabolic profile in four obese women who were previously exercise-trained for 15 months. This study therefore included regular aerobic exercise for 15 months and a low fat diet plus exercise for an additional period of 14 months. After 15 months, mean body weight and fat losses corresponded to 6.4 and 8.4 kg, respectively. Significant reductions (P less than 0.05) in plasma insulin, cholesterol, apo B, and LDL-C were also observed. Following the second part of the study, mean cumulative body weight and fat losses were 11.0 and 11.3 kg, respectively. At this time, the subjects were still overweight, but their plasma glucose and insulin during an oral glucose tolerance test were essentially similar to values obtained in a sample of 22 nonobese women. With the exception of plasma apo B and HDL-C levels, plasma lipid and lipoprotein levels were also comparable to those observed in nonobese controls. These results thus indicate that aerobic exercise-training and a low fat diet can normalize the metabolic profile of obese women, even if their adiposity remains higher than that of lean women.

Heredity and the path to overweight and obesity.

Abstract: Overweight and obesity are not homogeneous phenotypes as individuals differ in terms of the regional distribution of the excess weight or fat. Overweight and obesity are also complex multifactorial phenotypes influenced by both genetic and nongenetic determinants. Heritability of fat mass or percent body fat derived from underwater weighing measurement reaches about 25% of the age and gender adjusted phenotypic variance. Based on twin and parent-child data, it has been reported that the heritability of resting metabolic rate, thermic response to food, and energy cost of submaximal exercise, adjusted for the proper concomitants, is as high as 40%. The level of habitual physical activity also exhibits a significant heritability level on the order of about 25%. Experimental overfeeding with identical twins demonstrates that there are inherited differences in body weight and body composition response. The most important factor identified thus far to account for the individual differences in response to long-term overfeeding is a nutrient partitioning characteristic, namely the proportion of fat vs lean tissue gained. The high gainers are those storing energy primarily in the form of fat, while the low gainers are storing relatively more in the form of lean tissue.

Commingling analysis of generalized body mass and composition measures: The Quebec family study

Abstract: Human body mass and composition are heterogeneous phenotypes resulting from the combined effects of genes, environmental factors, and their interactions. In order to gain an understanding of the individual genetic determinants leading to obesity, we have initiated a systematic analysis of several measures of fatness and its phenotypes including: the body mass index (wt/ht2), fat mass, fat-free (lean) mass, the ratio of fat mass over fat-free mass, percent body fat, and a fat mass index (fat mass/ht). In this report, we examine the distributions of these age and sex adjusted variables in a large family study from Quebec in terms of evidence for commingling and skewness, and evaluate the inter-relationships among the measures. Fat mass, fat-free mass and the fat mass index conceptually represent primary variables in that they are quantitative measures of relevant components of total body weight; the hypothesis of a single distribution was inferred for each of these primary measures, with significant residual skewness except for fat mass. In general, offspring (8-26 years old) distributions were more positively skewed than parent (30-60 years old) distributions. The remaining variables (body mass index, fat mass to fat-free mass ratio, and percent body fat) are indexes combining information on fat and fat-free mass into single measures. Although offspring data were consistent with a single skewed distribution, commingling was found in the parents in each case. The prominent heterogeneity between generations suggests that there may be significant developmental (genetic or environmental) effects in the transition during growing years to adult pattern phenotypes, particularly for the complex indicators of body composition.

Maximal anaerobic performance of the knee extensor muscles during growth.

Abstract: The extent of the growth changes in maximal work output during 10 s (MWO10), 30 s (MWO30), and 90 s (MWO90) of maximal repetitive knee flexions and extensions assessed on a modified Hydra-Gym machine was investigated in 84 boys and 83 girls, 9-19 yr of age. Body weight, fat mass and fat free mass by underwater weighing, and thigh volume and cross-sectional area were also determined. No difference was observed in the absolute MWO10, MWO30, and MWO90 between girls and boys at 9 and 11 yr of age. However, significant differences appeared between genders from 13 yr of age onward, anaerobic performances of the knee extensor muscles of girls representing about 75% or even less of those of boys. The analysis of variance revealed that maximal work ouput during the three knee extension tests was significantly greater in males as well as in females from 9 to 18 yr, regardless how performance was related to morphological characteristics. Performance in absolute values or expressed per unit of body weight, fat free mass, and thigh cross-sectional area for the MWO10, MWO30, and MWO90 tests were almost always significantly lower in both genders when performances of the 9-yr-old group were compared with those of the 13-yr-old group or older groups. Improvement in maximal work output during the 10-s, 30-s, or 90-s knee extension tests with age occurred mainly between 9 and 15 yr in both genders. The results of the present study show that there are gender differences in predominantly anaerobic performances during growth and reveal that increase in muscle mass does not appear to be the only factor responsible for the age-related increment in the anaerobic working capacity of the knee extensor muscles.

Is weight fluctuation a risk factor

Abstract: Being overweight has reached epidemic proportions in the United States and Canada. In adults it is defined as having a body-mass index (the weight in kilograms divided by the square of the height i...

Genetics of obesity and human energy metabolism.

Abstract: Our understanding of the factors responsible for the individual differences in body fat content and the various components of energy expenditure is quite limited. We commonly recognize that there are individual differences within ethnic or racial groups living under given environmental and social conditions. Important correlates of these individual differences have been identified but they are not sufficient to draw a complete and integrated picture of all contributing elements. Our relative ignorance about the phenotypes, their assessment and all their affectors carries major implications for those interested in the genetics of body fat or obesity and energy metabolism. One consequence of this situation has been the total reliance up to now on the top-down approach (Sing et al. 1988) in studying the genetics of obesity and energy metabolism (Fig. 1). This is analogous to the situation that prevailed also, up until recently, in the investigation of the genetics of blood lipids-lipoproteins, atherosclerosis, coronary heart disease and other common diseases (Sing et al. 1988). Thus, a large number of reports have dealt with the heritability of the body mass index (BMI) or skinfold measurements (for reviews see Bouchard & PCrusse, 1988; Bouchard, 1989) and one study with body fat and fat-free mass derived from the underwater weighing assessment of body density (Bouchard et al. 1988a). In addition, three papers have been published on the familial resemblance or the heritability of resting metabolic rate (RMR; Fontaine et al. 1985; Bogardus et al. 1986; Bouchard et al. 1989), one on the heritability

Aerobic and anaerobic energy contribution during maximal work output in 90 s determined with various ergocycle workloads.

Abstract: The aim of this experiment was to evaluate the effect of different workloads on the relative contribution of the various energy delivery systems during a 90-s ergocycle test. Nine male subjects, 22 +/- 1 (mean +/- SD) years of age and weighing 71.4 +/- 6.8 kg, were submitted to a VO2max test, as 10-s test (0.1 kp/kg) and three 90-s tests at different loads (LO: 0.05, ME: 0.075 and HI: 0.1 kp/kg) on an ergocycle. No difference was found between peak power output during the 10-s and HI tests. No differences were observed in the total work output performed during 90 s at different workloads (between 481 and 495 J/kg) as well as in the contribution of aerobic and anaerobic pathways to total energy production. However, VO2max was reached earlier during the ME and HI tests than during the LO test. These results indicate that variation in workload did not influence the total work output and the total contribution of aerobic and anaerobic systems during maximal 90-s ergocycle performances. However, variation in workload had an impact on the relative aerobic and anaerobic contribution at various time points. It is concluded that a 90-s ergocycle test with a resistance of at least 0.1 kp/kg is required to appropriately assess maximal anaerobic power while anaerobic capacity might be measured with workloads as low as 0.05 kp/kg.

Heterogeneity among populations for familial aggregation of blood pressure

Abstract: A simple model of familial aggregation was applied to age-sex corrected systolic (SBP) and diastolic (DBP) blood pressure data from two separate studies: The Quebec Family Study and the Tecumseh Community Health Study. Examination of the familial correlations suggested heterogeneity across studies in all DBP correlations, but for SBP only spouse correlations were higher in Quebec. Fitting the path model to the data revealed that the only source of heterogeneity for SBP was in spouse resemblance (u), which was significant in Quebec but could be dropped from the model in Tecumseh. For SBP, no further heterogeneity was detected, with the vertical transmission being compatible with (but not evidence for) purely polygenic inheritance (i.e., τf = τm = 1/2). Familiality estimates (t2 ) for SBP were quite high (nearly 40%), and extra sibling resemblance was significant. For DBP, heterogeneity was detected in all parameters of the model except for spouse resemblance. Common sibship environmental effects (b) were of little importance in Tecumseh but were highly significant in Quebec. Vertical transmission from mothers (τm ) could be fixed at 1/2 in Tecumseh but was only about half as large in Quebec, and familiality estimates were higher in Quebec (nearly 60%) than in Tecumseh (about 25%). One source of the heterogeneity for SBP was due to cohabitation, which positively impacted on sibling correlations. The source of the sample heterogeneity in DBP may be through environmental factors which have a smaller impact in Tecumseh than in Quebec, although genetic heterogeneity could not be ruled out. Differences in the study designs, as well as differences in the two populations, could account for the heterogeneity detected.