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OBJECTIVE--To determine the effect of a 20-week endurance training program in healthy, previously sedentary participants on measures derived from an intravenous glucose tolerance test (IVGTT). RESEARCH DESIGN AND METHODS--An IVGTT [...]

We recently reported that a genomic region close to the leptin locus was linked to fasting insulin response to exercise training in nondiabetic white subjects. We tested the hypothesis that common exonic variants in the leptin (LEP) and leptin receptor (LEPR) genes modify the effects of regular physical activity on glucose homeostasis in nondiabetic whites (n = 397) and blacks (n = 143). In whites, exercise increased insulin sensitivity index (P = 0.041) and disposition index (P = 0.046) in the LEPR 109R allele carriers but not in the K109K homozygotes, increased glucose disappearance index more in the R109R homozygotes than in the K109 allele carriers (P = 0.039), and decreased fasting glucose only in the 109R allele carriers (P = 0.018). We also found an interaction between the LEP A19G and LEPR K109R polymorphisms on the change in fasting insulin in whites (P = 0.010). The association between the LEP A19G polymorphism and the change in insulin was evident only in the LEPR 109R carriers (P = 0.019). The decrease in insulin was strongest in the LEP Alga homozygotes who carried the LEPR 109R allele. Similar interaction was observed in blacks (P = 0.046). Variations in the LEP and LEPR genes are associated with the magnitude of the effects of regular exercise on glucose homeostasis in nondiabetic individuals., Type 2 diabetes is a multifactorial disease that results from a genetic predisposition and various behavioral and environmental risk factors (1). Regular physical activity has been associated with a reduced [...]

Background: A poor diet is a risk factor for chronic diseases such as obesity, cardiovascular disease, hypertension, and some cancers. Twin and family studies suggest that genetic factors potentially influence energy and nutrient intakes. Objective: We sought to identify genomic regions harboring genes affecting total energy, carbohydrate, protein, and fat intakes. Design: We performed a genomic scan in 347 white sibling pairs and 99 black sibling pairs. Dietary energy and nutrient intakes were assessed by using Willett's food-frequency questionnaire. Single-point and multipoint Haseman-Elston regression techniques were used to test for linkage. These subjects were part of the Health, Risk Factors, Exercise Training, and Genetics (HERITAGE) Family Study, a multicenter project undertaken by 5 laboratories. Results: In the whites, the strongest evidence of linkage appeared for dietary energy and nutrient intakes on chromosomes 1p21.2 (P = 0.0002) and 20q13.13 (P = 0.00007), and that for fat intake appeared on chromosome 12q14.1 (P = 0.0013). The linkage evidence on chromosomes 1 and 20 related to total energy intake rather than to the intake of specific macronutrients. In the blacks, promising linkages for macronutrient intakes occurred on chromosomes 12q23-q24.21, 1q32.1, and 7q11.1. Several potential candidate genes are encoded in and around the linkage regions on chromosomes 1p21.2, 12q 14.1, and 20q13.13. Conclusions: These are the first reported human quantitative trait loci for dietary energy and macronutrient intakes. Further study may refine these quantitative trait loci to identify potential candidate genes for energy and specific macronutrient intakes that would be amenable to more detailed molecular studies. KEY WORDS Gene, quantitative trait locus, inheritance, food preference, linkage, energy intake

Several genome-wide linkage scans have been carried out to identify quantitative trait loci for type 2 diabetes and related metabolic phenotypes. However, no previous linkage scans have focused on the response to exercise training of relevant metabolic traits. We performed a genome-wide linkage scan for baseline fasting glucose, insulin, and C-peptide and their responses to a 20-week exercise training program in nondiabetic white and black men and women from the HERITAGE Family Study. In SIBPAL linkage analyses, the maximum number of sibpairs available was 344 and 93 for baseline phenotypes and 300 and 72 for exercise training response phenotypes in whites and blacks, respectively. A total of 509 markers with an average spacing of 6.0 Mb were used. The strongest linkage was found for the changes in fasting insulin in response to exercise training with a marker in the leptin gene on 7q31 (empirical multipoint P = 0.0004) in whites. In blacks, the strongest linkage was observed for baseline fasting glucose on 12q13-q14 (empirical multipoint P = 0.0006). These regions harbor several potential candidate genes. The present findings may be important in identifying individuals at increased risk of developing type 2 diabetes and who are most likely to benefit from a physically active lifestyle., Type 2 diabetes is a multifactorial heterogeneous disease characterized by variable degrees of insulin resistance and pancreatic β-cell dysfunction, which together lead to glucose intolerance (1). Chronic hyperglycemia, even below [...]

This article attributes the heart rate and blood pressure similarities in Caucasian families to genetics. An analysis of systolic blood pressure, diastolic blood pressure, and oxygen consumption is presented.

Abdominal visceral fat (AVF), abdominal subcutaneous fat (ASF), and abdominal total fat (ATF) were measured using a computed tomography scan, both before (baseline) and after (post) a 20-week endurance exercise [...]

Research demonstrates that hormone replacement and vasodilatory property appear to show association at high intensity exercise. Further, favorable hemodynamic and oxygen consumption adaptations occur during endurance exercise training, which are independent of mensural status or hormone therapy.

This article discusses the hereditary aspects of ventilatory threshold. Topics include an analysis of oxygen consumption, aerobic fitness, and phenotype is presented.

This article examines the influence of sex, health status, and age on physiological responses to exercise training. Findings indicate that unhealthy individuals have more dramatic improvements in blood pressure levels, triglyceride concentrations, and cholesterol levels than healthy individuals and that women have a reduced training response when compared to men.

This article discusses research on genetic factors contributing to submaximal aerobic performance phenotypes taken before and after endurance training of 20 weeks. Results show that familial/genetic factors, especially maternal inheritance, influence response to endurance training of sedentary subjects.

This article discusses the contributions of fitness and fatness to potential risks for coronary heart disease, using sedentary adults. Results show that both fitness and fatness are important predictors of risk.

This article examines the effects of an aerobic exercise training program on stroke volume, cardiac output, and oxygen utilization in groups arranged by race, gender, and age. Results indicate that changes in cardiovascular function and level of adaption to intense physical training were similar across groups.

This article examines the effects of an aerobic training program on blood pressure and heart rate during rest and exercise in groups arranged by race, gender, and age. Results indicate that training significantly reduced blood pressure and heart rate during exercise with black and older participants experiencing the greatest changes.

Results show that in a 20-week training program, subjects exercising at a steady-state heart rate and steady maximum oxygen intake can substantially vary their training power out put and increases in rate of power out put.

Research was conducted to determine the reproducibility of cardiovascular, respiratory, and metabolic variables, during maximal exercise, in 390 HERITAGE Family members. Results show that reproducibility was high for all the parameters studied with little variation in the day-to-day measurements.

A muscle-specific creatine kinase (CKMM) gene may contribute to individual differences in maximal oxygen uptake responses to endurance training. Genetic linkage was found in 495 members of 98 Caucasian nuclear families. Researchers measured responses to both sedentary status and endurance training.

The equations developed by the HERITAGE Family Study to estimate oxygen consumption were in some ways superior to those produced by the American College of Sports Medicine (ACSM). The HERITAGE study's best equation was that using only power output, and yielded the most reliable predictions when utilizing pretraining data. Equations for post-training data, whether developed by HERITAGE or the ACSM, were equal in quality.

I provide an overview of the role of physical activity in the prevention of overweight and obesity and in the treatment of overweight and obese individuals. A secondary focus of this paper is on the potential mechanisms responsible for changes in body composition consequent to physical activity. The use of the term 'physical activity' is preferred to the term 'exercise' to better reflect a broader scope of movement, not limited to formal exercise regimes. A brief review of prospective studies that investigated alterations in body composition consequent to physical activity alone is presented, along with a discussion of the influence of genetics, macronutrients in the diet, and characteristics of exercise programs on the magnitude of change observed in these studies. This is followed by a review of the specific role of chronic physical activity on energy intake, resting metabolic rate, the thermic effect of feeding, and the thermic effect of activity. Finally, I discuss the role physical activity plays in preventing overweight and obesity and the most appropriate use of exercise in the management of overweight. Am J Clin Nutr 1996; 63(suppl):456S-60S.

The effects of a nonselective [beta]-adrenergic blocking agent with (pindolol) and without (propranolol) intrinsic sympathomimetic activity properties, compared with placebo-controlled conditions, on metabolic and cardiorespiratory function during long-duration (2 hours) physical activity were examined. After initial cardiorespiratory testing, subjects performed 2-hour walks at 25 and 45% of maximal oxygen consumption ([VO.sub.2]max) under each of the following 3 treatments: pindolol, propranolol and placebo. Medication distribution was randomized and double-blinded. A supine resting blood pressure and electrocardiogram were obtained before each exercise trial. Oxygen consumption, heart rate, stroke volume, cardiac output and blood pressure were determined after 5 minutes of quiet sitting and every 30 minutes during each 2-hour exercise trial. Cardiac output was not significantly different at rest or during exercise, comparing pindolol and propranolol with placebo conditions. Cardiac output tended to decrease over time earlier during propranolol treatment for the 25% [VO.sub.2]max trials in trained normotensive subjects than for the other treatments. Cardiac output decreased at approximately the same time across treatments during the 45% [VO.sub.2]max trials in trained normotensive and untrained hypertensive groups. Finally, owing to the observation that a reduction in cardiac output was delayed or prevented in trained normotensive subjects when compared with that in untrained hypertensives while exercising at 25% [VO.sub.2]max, developing a subject's cardiovascular fitness level may be important in the maintenance of cardiac output during extended periods of low-to-moderate physical activities while under the influence of [beta]-adrenergic blockade.

This study determined the effect on resting metabolic rate (RMR) of subjects spending the night before measurement at home vs at a clinic. Ten subjects participated in six randomized RMR measurements; three measurements were made after subjects slept the evening before the measurements in their home (H1, H2, and H3) and three after they slept in a clinical setting (C1, C2, and C3). There were no significant differences (P < 0.05) in oxygen consumption (V[O.sub.2], mL/min), RMR (kJ/min, kJ . kg body [wt.sub.-1] . [h.sub.-1], or kJ . kg fat-free [mass.sub.-1] . [h.sub.-1]), or respiratory exchange ratio (RER) between any of the six RMR measurements, or between mean values for the three home trials (V[O.sub.2] = 216 [+ or -] 41 mL/min, RER = 0.80 [+ or -] 0.04, heart rate = 51 [+ or -] 3 beats/min, ventilation = 7.1 [+ or -] 1.1 L/min) vs the three clinical trials (V[O.sub.2] = 216 [+ or -] 45 mL/min, RER = 0.80 [+ or -] 0.04, heart rate = 52 [+ or -] 5 beats/min, ventilation = 7.0 [+ or -] 1.1 L/min). We conclude that under most circumstances it is not important that subjects spend the night before RMR assessment at the measurement facility. However, when basal metabolic rate is to be assessed, an overnight stay at the clinical facility would generally be necessary. Am J Clin Nutr 1993;58: 141-4.

A study is conducted to explore sex and race differences in the association between changes in fat mass (FM), abdominal visceral fat (AVF), and abdominal subcutaneous fat (ASF) on blood lipid changes consequent to aerobic exercise training. The multivariate associations among fat loss and changes in blood lipids consequent to aerobic exercise training are similar in African American and white men and women.

A study was done of the Heritage family in a standardized 20 wk training program to investigate whether genetic factors influenced the response to training. It revealed that heart rate (HR) at a given %VO(sub 2max) was not affected by training in a large heterogeneous group of men and women, blacks and white, who varied in fitness, age and response to training.

Research demonstrates that patients with metabolic syndrome risk factors benefit from the aerobic exercise training, which prevents them from developing chronic disease. The metabolic syndrome risk factors include elevated waist circumference, blood pressure, triglycerides, blood glucose, an low high-density cholesterol.

Research reveals familial aggregation of energy metabolism enzyme activities in the skeletal muscle both in the sedentary state and in response to regular exercise. Data show familial resemblance for Type I fiber area and familial aggregation for energy metabolism enzyme in the sedentary state, while with regard to training response familial aggregation is observed only for enzyme activities.

The association between an Apa I restriction fragment length polymorphism (RFLP) in the IGF2 gene locus (IGF2/Apa I) and plasma glucose, insulin and C-peptide levels in the fasting state and [...]

Background: Obesity is a major public health problem in the United States. The role of physical activity and formal exercise in controlling body weight has not been clearly determined. Objective: This study determined the magnitude of change in body weight and composition across sex, race, and age in response to 20 wk of endurance training. Design: Men and women (n = 557) of various ages (16-65 y) and 2 races (black and white) exercised on cycle ergometers 3 d/wk for a total of 60 exercise sessions starting at 55% of maximal oxygen consumption ([VO.sub.2] max) for 30 min/session and building to 75% of [VO.sub.2] max for 50 min/session, where it was maintatined during the last 6 wk. Skinfold-thickness measurements, circumferences, body composition (by hydrostatic weighing), and body fat distribution (by computed tomography scan at L4-L5 and the waist-hip ratio) were determined before and after training. Results: All skinfold-thickness and circumference measures, waist-hip ratio, body mass index, total body mass, fat mass, percentage body fat, and computed tomography scan measures of total, subcutaneous, and visceral abdominal fat decreased with training, whereas total body density and fat-free mass increased. These changes were significant, but small. There were several differences in training response by sex and race, but not by age. Conclusions: A short-term exercise intervention can induce favorable changes in body composition, but the magnitude of these changes is of limited biological significance. Increasing physical activity likely has a major effect on body-composition and fat distribution characteristics only when it is of a greater magnitude and sustained for much longer periods Am J Clin Nutr 1999;70:346-52. KEY WORDS Body composition, fat mass, fat-free mass, visceral fat, skinfold thicknesses, endurance training, weight control, obesity, HERITAGE Family Study