The effects of eccentric and concentric resistance exercise on metabolic health

Title from PDF of title page (University of Missouri--Columbia, viewed on December 7, 2010).The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Dissertation advisor: Dr. Tom R. Thomas.Vita.Ph. D. University of Missouri--Columbia 2010.The purpose of this study was to 1) compare the effects of single sessions of eccentric (ECC) and concentric (CON) contractions, and 2) determine the effects of 12 wks of ECC and CON resistance training (RT) on parameters of metabolic health. Thirty sedentary and obese individuals were randomly assigned to complete a single session of either CON (n=15) or ECC (n=15) resistance exercise consisting of 3 sets of 10 repetitions of bilateral leg extension and leg curl at 75% of CON or ECC one repetition maximum (1RMCON/1RMECC). Outcome measures were assessed at baseline (0 h) and 1, 24, 48, and 72 h post-exercise. Twenty-five of the 30 subjects also completed 12 wks of CON (n=13) or ECC (n=12) RT. Training consisted of whole-body RT 3-4 d/wk at 60-75% of 1RMCON or 1RMECC. Outcome measures were assessed pre- and post-training. The single session of ECC exercise produced significantly greater muscle degradation than CON exercise. The single session of exercise significantly reduced plasma TG and lipoproteins; however, there were no differences in these reductions between groups. No significant differences were found for plasma cytokines, glucose, or insulin. RT resulted in significant reductions in body fat%, waist circumference, diastolic blood pressure, and mid-thigh adipose tissue (AT) and significant increases in muscular strength, lean body mass, and mid-thigh total- and high density-muscle with no significant group differences. There were no significant changes in abdominal AT, plasma TG, lipoproteins, cytokines, glucose, or insulin following RT. Although a single session of ECC contractions resulted in greater skeletal muscle degradation than CON, the effects on plasma metabolic variables were similar in the two groups. Both CON and ECC RT produce beneficial alterations in metabolic health.Includes bibliographical reference

Positive association between mammographic breast density and bone mineral density in the Postmenopausal Estrogen/Progestin Interventions Study

INTRODUCTION: Mammographic breast density is a strong independent risk factor for breast cancer. We hypothesized that demonstration of an association between mammographic breast density and bone mineral density (BMD) would suggest a unifying underlying mechanism influencing both breast density and BMD. METHODS: In a cross-sectional analysis of baseline data from the Postmenopausal Estrogen/Progestin Interventions Study (PEPI), participants were aged 45 to 64 years and were at least 1 year postmenopausal. Mammographic breast density (percentage of the breast composed of dense tissue), the outcome, was assessed with a computer-assisted percentage-density method. BMD, the primary predictor, was measured with dual-energy X-ray absorptiometry. Women quitting menopausal hormone therapy to join PEPI were designated recent hormone users. RESULTS: The mean age of the 594 women was 56 years. The average time since menopause was 5.6 years. After adjustment for age, body mass index, and cigarette smoking, in women who were not recent hormone users before trial enrollment (n = 415), mammographic density was positively associated with total hip (P = 0.04) and lumbar (P = 0.08) BMD. Mammographic density of recent hormone users (n = 171) was not significantly related to either total hip (P = 0.51) or lumbar (P = 0.44) BMD. In participants who were not recent hormone users, mammographic density was 4% greater in the highest quartile of total hip BMD than in the lowest. In participants who were not recent hormone users, mammographic density was 5% greater in the highest quartile of lumbar spine BMD than in the lowest. CONCLUSION: Mammographic density and BMD are positively associated in women who have not recently used postmenopausal hormones. A unifying biological mechanism may link mammographic density and BMD. Recent exogenous postmenopausal hormone use may obscure the association between mammographic density and BMD by having a persistent effect on breast tissue

Predicting Postprandial Lipemia in Healthy Adults and in At-Risk Individuals With Components of the Cardiometabolic Syndrome

To determine whether a single‐point triglyceride (TG) concentration could estimate the 8‐hour postprandial lipemic (PPL) response, men and women performed baseline PPL (n=188) and postexercise PPL (n=92) trials. Correlations were generated between TG concentrations at baseline and at various time points after a high‐fat meal vs 8‐hour area under the TG curve (TG‐AUC) and peak TG level. Stepwise multiple regression and bootstrap simulations using TG level and additional predictor variables of sex, age, percentage of body fat, training status, and maximal oxygen consumption indicated that the 4‐hour TG concentrations accounted for \u3e90% of the variance in TG‐AUC and peak TG responses during the PPL trials. Equations were confirmed by cross‐validation in healthy as well as at‐risk individuals with components of the cardiometabolic syndrome. Our data suggest that the 4‐hour TG value is highly related to the total 8‐hour PPL response and can be used for accurate estimation of PPL in a clinical or research setting