Biomedical subjects

C Bouchard

Publications and source records attributed to C Bouchard.

At least 559 records · Page 31Linked to original sources

PubMed1986

Heredity and changes in hormones and metabolic rates with short-term training.

The purpose of this experiment was to assess the effects of a 22-day training program on resting metabolic rate (RMR), thermic effect of a meal (TEM), and associated hormonal changes. Six pairs of male monozygotic twins were submitted to a 22-day ergocycle exercise program designed to induce a deficit in energy balance of 4.2 MJ per day. RMR and TEM after a 4.2-MJ meal challenge were measured before and after training. Results indicated that RMR and TEM did not change significantly, although a large variation in response between twin pairs was observed. Moreover, training reduced (P less than 0.05) basal and postprandial insulin response, plasma thyroid hormones triiodothyronine (T3), thyroxine (T4), and FT4 (P less than 0.05). Absolute changes in RMR and TEM exhibited significant within-pair resemblance in response, with intraclass correlations reaching r = 0.81 (P less than 0.05) and r = 0.72 (P less than 0.05), respectively. Changes in T4 and FT4 also exhibited moderate within-pair resemblance (0.42 less than or equal to r less than or equal to 0.71). These results suggest that short-term exercise training does not modify RMR and TEM but can significantly decrease plasma levels of insulin and thyroid hormones. Moreover, the similarity of response within twin pairs suggests that heredity plays a role in determining RMR, TEM, and thyroid hormone adaptation to exercise training generating a negative energy balance.

Adolescent↗

PubMed1986

Skeletal muscle characteristics in sedentary black and Caucasian males.

Twenty-three male Black African and 23 male Caucasian subjects, ascertained as sedentary, participated in this study designed to determine whether there were differences in skeletal muscle histochemical and biochemical characteristics between racial groups. Muscle fiber type proportions (I, IIa, and IIb), fiber areas and activities of several enzyme markers of different energy metabolic pathways were determined from a biopsy of the vastus lateralis. Results indicated that Caucasians had a higher percent type I (8%, P less than 0.01) and a lower percent type IIa (6.7%, P less than 0.05) fiber proportions than Africans. No significant differences were observed between the two racial groups in the type IIb fiber proportion or in the three fiber type areas. Enzymes catalyzing reactions in phosphagenic [creatine kinase (CK)] and glycolytic [hexokinase (HK), phosphofructokinase (PFK), and lactate dehydrogenase (LDH)] metabolic pathways had significantly higher activities (about 30-40%) in the Black African group than in the Caucasian group (P less than 0.01). No significant difference was noted in the activities of oxidative enzymes [malate dehydrogenase (MDH), oxoglutarate dehydrogenase (OGDH), and 3-hydroxyacyl-CoA dehydrogenase (HADH)]. Consequently, the PFK/OGDH ratio was significantly elevated in Africans (P less than 0.05). The racial differences observed between Africans and Caucasians in fiber type proportion and enzyme activities of the phosphagenic and glycolytic metabolic pathways may well result from inherited variation. These data suggest that sedentary male Black individuals are, in terms of skeletal muscle characteristics, well endowed for sport events of short duration.

Adult↗

PubMed1986

Inheritance of human muscle enzyme adaptation to isokinetic strength training.

Five monozygotic twin pairs were submitted to a 10-week isokinetic strength training program and biochemical characteristics measured before and after training to determine the role of heredity in skeletal muscle adaptation, while 5 unrelated sedentary subjects served as control group. Experimental subjects performed twice 3 series of 5 bilateral reciprocal alternating knee flexions and extensions at a velocity of 90 degrees/s 5 times per week. Before and after the training period, for each subject, the peak muscular torque output was measured at the same velocity and the vastus lateralis muscle was biopsied for biochemical determinations. No significant change was observed in the control group. Training increased peak muscular torque output by 24%. The activities of hexokinase, malate dehydrogenase and 3-hydroxyacyl CoA dehydrogenase also increased significantly by 28, 26 and 38%, respectively. Interindividual variations in the response of these variables to training were noted but these were shown to be independent of the genotype. No overall effect of training was observed for oxoglutarate dehydrogenase activity (OGDH). However, changes were seen in individual pairs of twins and these were in opposite directions in some pairs compared to others, thus explaining the absence of a general training effect. Significant intrapair resemblance in the training response was present for OGDH (r = 0.76), indicating that the sensitivity to isokinetic strength training for OGDH was highly variable, not random and probably genetically determined.

3-Hydroxyacyl CoA Dehydrogenases↗

PubMed1986

The effect of exercise-training on resting metabolic rate in lean and moderately obese individuals.

Two experiments have been performed to establish whether exercise-training has an influence on resting metabolic rate (RMR). In a first study, RMR was measured in a cohort of 59 individuals comprising 20 trained and 39 non-trained subjects. The absolute level of RMR in trained subjects exceeded by 11 percent that observed in the non-trained individuals (P less than 0.01). When comparing regression lines of RMR versus FFM between the two groups, the intercept with the Y axis (RMR values) was also significantly higher in trained subjects (P less than 0.01). The second experiment was conducted to find out whether the trend for an elevated RMR noted in athletes could be reproduced in obese persons engaging in an exercise-training program. Eight moderately obese women were submitted to an 11-week training programme, including 5 hours of aerobic exercise per week performed at a mean intensity of about 50 percent VO2 max. The results showed that exercise-training induced a significant rise in RMR which corresponded to 8 percent of pretraining value in kcal/kg FFM/min (P less than 0.01). Thus, data reported here suggest that aerobic exercise-training is associated with an elevated RMR per unit of fat free mass in both lean and moderately obese individuals.

Adult↗

PubMed1986

The role of body fat in insulin sensitivity of endurance athletes.

The purpose of the study was to assess the role of adiposity in the enhanced insulin sensitivity observed in endurance athletes (EA). An oral glucose tolerance test (75 g glucose) was administered to nine EA and to 23 sedentary subjects (SS). Two different strategies were used to investigate the problem. First, body composition indicators and Vo2max were correlated with the delta insulin and delta glucose areas measured for 180 minutes following glucose ingestion. These correlation analyses were performed for the two groups combined (n = 32). No significant correlations were observed between either fat weight or percent body fat versus delta insulin, delta glucose or delta glucose/delta insulin areas. Moreover, no significant correlation was observed between the several subcutaneous fat indicators and delta insulin, delta glucose and delta glucose/delta insulin areas. The second strategy consisted of comparing EA to SS when percent body fat difference was eliminated. This was achieved by two different methods, first by covariance analysis and second by comparing subsamples of trained and non-trained subjects paired with respect to percent body fat. These two comparisons revealed that even when adiposity was equal between the groups, a significantly greater insulin sensitivity was observed in the EA group (p less than 0.01). The present results suggest that adiposity is not the determining factor for the increased insulin sensitivity of trained subjects.

Adipose Tissue↗

PubMed1986

Fat distribution and adipose tissue metabolism in non-obese male black African and Caucasian subjects.

Twenty-four male black African (25.5 +/- 3.0, mean +/- s.d., years of age) and 24 male Caucasian (21.5 +/- 3.6) subjects, ascertained as sedentary individuals, participated in this study designed to determine whether there were racial differences in fat distribution and adipose tissue metabolism while controlling the differences in body fat. An adipose tissue biopsy was obtained from the suprailiac region for the determination of basal (BL), epinephrine submaximal 10(-4) M (ESML) and maximal 10(-3) M (EML) stimulated lipolysis, basal (BLG) and maximal insulin 9 microU/ml (ILG) stimulated lipogenesis and heparin releasable lipoprotein lipase (LPL) activity. Body density was determined through underwater weighing procedures and body fat derived with the Siri equation. The following skinfolds were also measured: triceps, biceps, subscapular, abdomen, suprailiac, front thigh and medial calf. Caucasians were matched with the black Africans for age, body weight and body density. Results indicated that when Caucasians and black Africans of similar percentage body fat were compared, no significant differences were observed in the total amount of subcutaneous fat, fat distribution and suprailiac mean fat cell size. Moreover, no significant differences were observed between the two groups for BL, BLG, and ILG of adipose tissue. However, black Africans had higher (P less than 0.01) epinephrine stimulated lipolytic values (ESML and EML) and LPL activity (P less than 0.01) than the Caucasian subjects. These results suggest that for a comparable level of fatness and similar fat morphology and distribution, there are racial differences in adipose tissue metabolism.

Adipose Tissue↗

PubMed1986

More on red blood cell genetic variation in Olympic athletes.

As a follow-up to De Garay et al. (1976) and Chagnon et al. (1984) studies, we are reporting on the genetic variation of four red blood cell enzymes in 49 athletes with isoelectric-focusing and electrophoresis techniques. The athletes were Caucasians participating in the 1976 Montreal Olympic Games. They were performing in 5 different sports and the sample included 18 women and 31 men. No uncommon allele was found and all known alleles were detected for each enzyme. Phenotypes and gene frequencies were computed and compared with appropriate populations of reference. No significant differences were observed for any of the enzymes. Moreover, no association was found between variation in these proteins and participation in rowing (N = 25) or track (N = 13) event.

Acid Phosphatase↗

PubMed1986

Aerobic performance in brothers, dizygotic and monozygotic twins.

Forty-two brothers, 66 dizygotic twins of both sexes and 106 monozygotic twins of both sexes, 16 to 34 yr of age, took part in this study that was designed to investigate the effect of heredity in aerobic performance. Maximal oxygen uptake (VO2 max), maximal heart rate (HR max), maximal ventilation, and maximal oxygen pulse were obtained from a progressive ergocycle test to exhaustion. Total work output in a 90-min maximal ergocycle test was also determined in the twins. Fat-free weight was estimated from body density measurements obtained through underwater weighing. Aerobic performance scores were adjusted for age (brothers), and age and sex (dizygotic and monozygotic twins) by regression procedures. Dizygotic twins and brothers of same sibship exhibited about the same level of resemblance for all variables or were only slightly different, with the exception of HR max. Monozygotic pairs were generally more alike than the other sibs, as suggested by the intra-class coefficients. Twin data were used to compute the genetic effects. The within-pair estimate of genetic variance revealed that it was significant (P less than or equal to 0.05) for all variables except VO2 max X kg-1 fat-free weight X min-1. In the case of HR max, the among-pairs component estimate had to be used, and it also proved significant (P less than or equal to 0.01). The size of the genetic effect was computed from three different methods, and it reached about 40% for VO2 max X kg-1 X min-1, 50% for HR max, 60% for maximal oxygen pulse and maximal ventilation, and 70% for 90-min work output X kg-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1986

Heredity and muscle adaptation to endurance training.

To determine whether sensitivity of muscle characteristics and aerobic performances to endurance training was genotype-dependent, 6 pairs of monozygotic (MZ) twins, 21 +/- 4 yr of age (mean +/- SD), took part in a 15-wk ergocycle endurance training program. Tests were performed before and after 7 and 15 weeks of training. A biopsy of the vastus lateralis muscle was obtained for the determination of fiber type composition and activities of creatine kinase, hexokinase, phosphofructokinase, lactate dehydrogenase, malate dehydrogenase, 3-hydroxyacyl CoA dehydrogenase, and oxoglutarate dehydrogenase. Maximal oxygen uptake was measured with a progressive maximal ergocycle test, while endurance performance was determined as the total work output during a 90-min maximal ergocycle test. Results indicated that maximal oxygen uptake X kg-1 and endurance performance X kg-1 increased significantly (14 and 31%, respectively) with training, and intra-pair resemblance (intra-class) in response to 15 wk of training ranged from 0.65 to 0.83. Hexokinase (31%), phosphofructokinase (37%), lactate dehydrogenase (21%), malate dehydrogenase (31%), and 3-hydroxyacyl CoA dehydrogenase (60%) were significantly increased with training whereas no mean change in fiber-type proportions, oxoglutarate dehydrogenase and creatine kinase activities and the phosphofructokinase/oxoglutarate dehydrogenase ratio was observed. Similarity within twin pairs in the response to enzyme activities was mainly detected in the second half of the training program. The present results confirm, therefore, that both maximal oxygen uptake and endurance performance responses to training are largely genotype-dependent.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗

PubMed1985

Cardiac dimension changes with endurance training. Indications of a genotype dependency.

We studied the sensitivity of cardiac structures to endurance training. To evaluate variability in adaptation, 20 sedentary subjects and ten pairs of monozygotic twins were submitted to a 20-week endurance training program. Maximal oxygen uptake increased significantly in both groups: 11 mL O2/kg/min-1 or 30% in the sedentary group and 6 mL O2/kg/min-1 or 13% in the monozygotic twins. Statistically significant increases in left ventricular diameter, posterior wall and septal thicknesses, as well as left ventricular end-diastolic volume and left ventricular mass were observed in the sedentary subjects, but not in the monozygotic twins. We could demonstrate that after training, twin pairs differed more from each other than at the start. Concomitantly, within-pair resemblance was greater after training than before. Results indicate that cardiac dimensions are amenable to significant modifications under controlled endurance training conditions and furthermore that the extent and variability of the response of cardiac structures to training are perhaps genotype dependent.

Adult↗

PubMed1985

Relationships between skeletal muscle characteristics and aerobic performance in sedentary and active subjects.

Forty-eight sedentary and 39 quite active or well-trained men participated in this study. Muscle biopsy samples were taken from the vastus lateralis for the determination of fiber type composition (I, IIa, IIb), fiber type area, and assay of the following enzymes: malate dehydrogenase (MDH), 3-hydroxyacyl CoA dehydrogenase (HADH) and oxoglutarate dehydrogenase (OGDH). Maximal oxygen uptake (VO2max) was determined with a progressive cycle ergometer test, while endurance performance or maximal aerobic capacity (MAC) was defined as the total work output during a 90-min cycle ergometer test. Correlation analysis revealed no evidence of association between fiber type composition and VO2max kg-1 or MAC kg-1 in sedentary subjects, while active men exhibited significant correlation between % type I (r = 0.52), % type IIb (r = 0.31) and VO2max kg-1. Enzyme activities were not significantly correlated with MAC kg-1 and VO2max kg-1 in sedentary men while active men exhibited significant correlation for the three enzymes (0.37 less than or equal to r less than or equal to 0.51) with VO2max kg-1. These results show that the contribution of muscle fiber type and enzyme activities to aerobic performance may be inflated from a statistical point of view by the training status heterogeneity of subjects. They also suggest that variation in these muscle characteristics does not account for the individual differences in aerobic performance of subjects who have never trained before. Therefore, the assessment of muscle characteristics is not as useful as originally thought for the detection of individuals with a high potential for endurance performance among untrained subjects.

Adolescent↗

PubMed1985

Human skeletal muscle fiber type alteration with high-intensity intermittent training.

The response of muscle fiber type proportions and fiber areas to 15 weeks of strenuous high-intensity intermittent training was investigated in twenty-four carefully ascertained sedentary (14 women and 10 men) and 10 control (4 women and 6 men) subjects. The supervised training program consisted mainly of series of supramaximal exercise lasting 15 s to 90 s on a cycle ergometer. Proportions of muscle fiber type and areas of the fibers were determined from a biopsy of the vastus lateralis before and after the training program. No significant change was observed for any of the histochemical characteristics in the control group. Training significantly increased the proportion of type I and decreased type IIb fibers, the proportion of type IIa remained unchanged. Areas of type I and IIb fibers increased significantly with training. These results suggest that high-intensity intermittent training in humans may alter the proportion of type I and the area of type I and IIb fibers and in consequence that fiber type composition in human vastus lateralis muscle is not determined solely by genetic factors.

Adult↗

PubMed1985

High density lipoprotein cholesterol, habitual physical activity and physical fitness.

The relationships between habitual physical activity and fitness parameters and fasting serum high density lipoprotein cholesterol (HDL-C), total cholesterol (TC), and triglycerides (TG) were assessed in 357 men aged 30-59 years (mean 44, SD 5). A progressive submaximal power output test (PWC150), a 1-min sit-up test, and a 3-day activity energy expenditure record were obtained for each subject. HDL-C, TG, and HDL-C/TC were significantly associated with the fitness indices (PWC150 and sit-ups), but not with the mean daily energy expenditure computed from a 3-day activity record. However, when the subjects were stratified according to the maximal level of intensity reported in the work and leisure energy expenditure record, a relationship between maximal exercise or work intensity and the concentration of HDL-C and TG, and the ratio HDL-C/TC was found. When adjusted by multiple regression procedures for age, alcohol consumption, cigarette smoking, socio-economic status, fatness level, and TC, or TG, or HDL-C, as appropriate, these relationships became nonsignificant, with the exception of TG and PWC150. These results suggest that habitual physical activity of light intensities is not a major determinant of HDL-C, TC, and HDL-C/TC; it could, however, have a small but significant role in TG. In addition, data suggest that periods of exercise of higher intensity, i.e. with an energy cost of about 6 mets and more, could be a sensible mean to influence serum blood lipid levels.

Adult↗

PubMed1985

Lack of relationship between changes in adiposity and plasma lipids following endurance training.

In order to study the effect of alterations in fat morphology and metabolism induced by exercise-training on plasma lipids, 13 healthy young men were subjected to a 20-week aerobic training program on bicycle. Training significantly increased maximal aerobic power (VO2 max) (P less than 0.001) and decreased per cent body fat (P less than 0.001). A significant reduction of mean adipocyte diameter and an increase in isolated fat cell epinephrine-stimulated lipolysis were also observed following training. However, with the exception of total cholesterol, no changes were noted in plasma lipids. Neither before nor after training were triglycerides and high density lipoprotein cholesterol (HDL-C) correlated with VO2 max, fat cell diameter and adipocyte-stimulated lipolysis. The present study demonstrates that an important fat loss (mean loss of fat = 3 kg) and a significant gain in VO2 max induced by endurance training do not necessarily produce an increase in HDL-C levels in normal male subjects. Moreover, changes in VO2 max, body fatness and in fat cell epinephrine-stimulated lipolysis produced by endurance training are not related to modifications in plasma lipids in healthy men.

Adipose Tissue↗

PubMed1985

Evidence for a regional component of body fatness in the association with serum lipids in men and women.

Four hundred and seventy-two subjects (234 women and 238 men), 18 to 50 years of age, participated in percent body fat determination from underwater weighing, assessment of 6 subcutaneous skinfold thicknesses, and a 12-hour fast blood sampling for measurement of serum triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), total cholesterol (CHOL), and HDL-C/CHOL ratio. Even though women were significantly fatter than men, they had lower TG, CHOL, and higher values of HDL-C/CHOL ratio. Correlational and variance analyses showed that body fatness seemed to be more closely associated with serum lipids in men than in women. Moreover, the relationship between each skinfold and serum lipids indicated that subscapular and abdominal fat depots are more closely associated with serum lipids than other fat depots in men. In women, correlations were lower and regional differences attenuated. Furthermore, the regional trend observed in men remained significant after correction for concomitant variables such as age, cigarette smoking, habitual energy intake and energy expenditure, maximal aerobic power, and alcohol consumption. However, no effect of increasing body fatness was noted on HDL-C levels in women. Results of this study suggest that measurement of subscapular and abdominal fat should be considered when interpreting the blood lipid profile, particularly in males. A higher percentage of fat must be present in women than in men to observe alterations in serum lipids.

Adipose Tissue↗

PubMed1985

Resting metabolic rate in monozygotic and dizygotic twins.

In order to study the influence of heredity on resting metabolic rate (RMR), 20 monozygotic and 19 dizygotic male twins pairs aged 20.6 (SD 2.9) and 21.4 (SD 3.1) years, gave their consent to participate in the experiment. Fat free weight (FFW) was estimated from underwater weighing. RMR was measured by indirect calorimetry using an open circuit system. RMR was expressed as kJ X min-1, kJ/m2 X h-1, kJ/kg X h-1 and kJ/kgFFW X h-1. Significant intraclass coefficients were observed in MZ twins for the different expressions of RMR. The values ranged from r = 0.45 (P less than 0.05) to r = 0.81 (P less than 0.01). However, DZ twins demonstrated lower intraclass coefficients for RMR, with a range from r = 0.21 to r = 0.44. Significant (P less than 0.05) DZ resemblance was revealed only when RMR was expressed as kJ X min-1 and kJ/kg X h-1. Results of the present study suggest that variations in RMR may have a genetic component. Implications for human energy balance and body fat are discussed.

Adipose Tissue↗

PubMed1985

Adipose tissue lipid accumulation pathways in marathon runners.

Eighteen male marathon runners (mean marathon performance: 2 h 36 min, SD = 7.0 min; VO2 max = 64.1 +/- 15.1 ml/kg . min-1) were submitted to a needle biopsy in the suprailiac region and to various measurements of body fatness: percent body fat (% fat), seven skinfold thicknesses, and mean fat cell diameter. Basal and insulin-stimulated glucose conversion into triglycerides were measured in collagenase-isolated fat cells, while heparin-releasable lipoprotein lipase activity (LPLa) was determined in intact adipose tissue. All body fatness indicators were significantly smaller in marathon runners in comparison to a sedentary control group (P less than 0.001). Fat cell basal and insulin-stimulated glucose conversion into triglycerides as well as LPLa were significantly higher for the runners group (P less than 0.01), differences being particularly important when comparisons were performed between subjects paired for mean fat cell diameter. Pearson interclass correlations between body fatness and fat cell glucose incorporation into triglycerides were low and positive for the sedentary group (0.04 less than or equal to r less than or equal to 0.41), while they were negative for the marathon runners groups (-0.28 less than or equal to r less than or equal to -0.40) with the exception of % fat. Moreover, correlations between LPLa and indicators of body fatness were positive in the sedentary group (0.47 less than or equal to r less than or equal to 0.79), while they were negative in the marathon runners group (-0.03 less than or equal to r less than or equal to -0.63).(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

PubMed1985

Specificity of aerobic and anaerobic work capacities and powers.

Thirty-three untrained subjects of both sexes, 18-31 years of age, performed several tests on cycle ergometers. Maximal aerobic power (MAP) was obtained in a progressive work test. Maximal aerobic capacity (MAC) was measured in a 90-min maximal test and was computed as the total work output during that period. Two all-out cycle ergometer work tests lasting 10 s and 90 s were used to estimate the anaerobic alactic capacity (AAC) and lactic capacity (ALC). Anaerobic alactic power (AAP) was computed as the highest output in 1 s in the AAC test and anaerobic lactic power (ALP) was obtained as the mean output during the last 5 s in an all-out test of 30 s. Correlation coefficients were computed between all measurements of capacity and power expressed per kg of body weight as well as with scores adjusted for sex differences. Common variances (r2 X 100) between measurements of power were either low (MAP-AAP, 40%) or moderate (MAP-ALP, 61%; AAP-ALP, 62%) while common variances between measurements of capacity were sometimes low (MAC-AAC, 49%) or higher (MAC-ALC, 76%; AAC-ALC, 77%). The common variances between tests of power and capacity reached high values when calculated with metabolic criteria of the same class (MAP-MAC, 81%; AAP-AAC, 92%). These results provide quantitative evidence to support the notion of specificity between the aerobic and the anaerobic work performances and support the distinction between capacity and power of the three energy systems.

Adenosine Triphosphate↗