Effect of exercise intensity and volume on persistence of insulin sensitivity during training cessation

Effect of exercise intensity and volume on persistence of insulin sensitivity during training cessation. J Appl Physiol 106: 1079â 1085, 2009. First published February 5, 2009; doi:10.1152/japplphysiol.91262.2008. The purpose of this study was to determine whether exercise prescriptions differing in volume or intensity also differ in their ability to retain insulin sensitivity during an ensuing period of training cessation. Sedentary, overweight/obese subjects were assigned to one of three 8-mo exercise programs: 1) low volume/moderate intensity [equivalent of 12 miles/wk, 1,200 kcal/wk at 40-55% peak O2 consumption (VO2peak), 200 min exercise/wk], 2) low volume/vigorous intensity (12 miles/wk, 1,200 kcal/wk at 65-80% VO2peak, 125 min/wk), and 3) high volume/vigorous intensity (20 miles/wk, 2,000 kcal/wk at 65-80% VO2peak, 200 min/wk). Insulin sensitivity (intravenous glucose tolerance test, SI) was measured when subjects were sedentary and at 16-24 h and 15 days after the final training bout. SI increased with training compared with the sedentary condition (P less than or equal to 0.05) at 16-24 h with all of the exercise prescriptions. SI decreased to sedentary, pretraining values after 15 days of training cessation in the low-volume/vigorous-intensity group. In contrast, at 15 days SI was significantly elevated compared with sedentary (P less than or equal to 0.05) in the prescriptions utilizing 200 min/wk (low volume/moderate intensity, high volume/vigorous intensity). In the high-volume/vigorous-intensity group, indexes of muscle mitochondrial density followed a pattern paralleling insulin action by being elevated at 15 days compared with pretraining; this trend was not evident in the low-volume/moderateintensity group. These findings suggest that in overweight/obese subjects a relatively chronic persistence of enhanced insulin action may be obtained with endurance-oriented exercise training; this persistence, however, is dependent on the characteristics of the exercise training performed

Mitochondrial Overload and Incomplete Fatty Acid Oxidation Contribute to Skeletal Muscle Insulin Resistance

SummaryPrevious studies have suggested that insulin resistance develops secondary to diminished fat oxidation and resultant accumulation of cytosolic lipid molecules that impair insulin signaling. Contrary to this model, the present study used targeted metabolomics to find that obesity-related insulin resistance in skeletal muscle is characterized by excessive β-oxidation, impaired switching to carbohydrate substrate during the fasted-to-fed transition, and coincident depletion of organic acid intermediates of the tricarboxylic acid cycle. In cultured myotubes, lipid-induced insulin resistance was prevented by manipulations that restrict fatty acid uptake into mitochondria. These results were recapitulated in mice lacking malonyl-CoA decarboxylase (MCD), an enzyme that promotes mitochondrial β-oxidation by relieving malonyl-CoA-mediated inhibition of carnitine palmitoyltransferase 1. Thus, mcd−/− mice exhibit reduced rates of fat catabolism and resist diet-induced glucose intolerance despite high intramuscular levels of long-chain acyl-CoAs. These findings reveal a strong connection between skeletal muscle insulin resistance and lipid-induced mitochondrial stress

Exercise-Induced Changes in Metabolic Intermediates, Hormones, and Inflammatory Markers Associated With Improvements in Insulin Sensitivity

OBJECTIVE: To understand relationships between exercise training-mediated improvements in insulin sensitivity (S(I)) and changes in circulating concentrations of metabolic intermediates, hormones, and inflammatory mediators. RESEARCH DESIGN AND METHODS: Targeted mass spectrometry and enzyme-linked immunosorbent assays were used to quantify metabolic intermediates, hormones, and inflammatory markers at baseline, after 6 months of exercise training, and 2 weeks after exercise training cessation (n = 53). A principal components analysis (PCA) strategy was used to relate changes in these intermediates to changes in S(I). RESULTS: PCA reduced the number of intermediates from 90 to 24 factors composed of biologically related components. With exercise training, improvements in S(I) were associated with reductions in by-products of fatty acid oxidation and increases in glycine and proline (P < 0.05, R² = 0.59); these relationships were retained 15 days after cessation of exercise training (P < 0.05, R² = 0.34). CONCLUSIONS: These observations support prior observations in animal models that exercise training promotes more efficient mitochondrial β-oxidation and challenges current hypotheses regarding exercise training and glycine metabolism

Infants’ behavioral and physiological profile and mother–infant interaction

This study aims to (a) identify and profile groups of infants according to their behavioral and physiological characteristics, considering their neurobehavioral organization, social withdrawal behavior, and endocrine reactivity to stress, and to (b) analyze group differences in the quality of mother–infant interaction. Ninety seven 8-week-old infants were examined using the Neonatal Behavioral Assessment Scale and the Alarm Distress Baby Scale. Cortisol levels were measured both before and after routine inoculation between 8 and 12 weeks. At 12 to 16 weeks mother–infant interaction was assessed using the Global Rating Scales of Mother–Infant Interaction. Three groups of infants were identified: (a) ‘‘withdrawn’’; (b) ‘‘extroverted’’; (c) ‘‘underaroused.’’ Differences between them were found regarding both infant and mother behaviors in the interaction and the overall quality of mother–infant interaction. The identification of behavioral and physiological profiles in infants is an important step in the study of developmental pathways

Assessing Psychological Well-Being in Mothers of Children with Disability: Evaluation of the Parenting Morale Index and Family Impact of Childhood Disability Scale

Objective Process model of stress and coping guided psychometric assessment of two brief measures of psychological well-being: Parenting Morale Index (PMI); Family Impact of Childhood Disability (FICD) scale. Methods Canadian mothers (N = 195) of children with disability (CWD) completed PMI, FICD, and validation measures (Brief Family Assessment Measure [FAM], Personal Well-Being Index, Positive and Negative Affect Schedule, General Self-Efficacy Scale, Social Desirability Scale) via computer-assisted telephone interview. Of these, 154 completed additional validation measures (Center for Epidemiological Studies—Depression Scale, Parenting Stress Index, Family Hardiness Index, Brief FAM) 1 year later. Results Factor structures of PMI and FICD were supported; both demonstrated internal consistency, temporal stability, and convergent and discriminant validity. After 1 year, PMI and FICD jointly predicted depressive symptoms, parenting stress, family hardiness, and family adjustment. Conclusion PMI and FICD can identify mothers of CWD at risk for poor psychological well-being to increase the specificity of supports

Abdominal obesity and metabolic syndrome: exercise as medicine?

Background: Metabolic syndrome is defined as a cluster of at least three out of five clinical risk factors: abdominal (visceral) obesity, hypertension, elevated serum triglycerides, low serum high-density lipoprotein (HDL) and insulin resistance. It is estimated to affect over 20% of the global adult population. Abdominal (visceral) obesity is thought to be the predominant risk factor for metabolic syndrome and as predictions estimate that 50% of adults will be classified as obese by 2030 it is likely that metabolic syndrome will be a significant problem for health services and a drain on health economies.Evidence shows that regular and consistent exercise reduces abdominal obesity and results in favourable changes in body composition. It has therefore been suggested that exercise is a medicine in its own right and should be prescribed as such. Purpose of this review: This review provides a summary of the current evidence on the pathophysiology of dysfunctional adipose tissue (adiposopathy). It describes the relationship of adiposopathy to metabolic syndrome and how exercise may mediate these processes, and evaluates current evidence on the clinical efficacy of exercise in the management of abdominal obesity. The review also discusses the type and dose of exercise needed for optimal improvements in health status in relation to the available evidence and considers the difficulty in achieving adherence to exercise programmes. Conclusion: There is moderate evidence supporting the use of programmes of exercise to reverse metabolic syndrome although at present the optimal dose and type of exercise is unknown. The main challenge for health care professionals is how to motivate individuals to participate and adherence to programmes of exercise used prophylactically and as a treatment for metabolic syndrome

Effects of exercise amount and intensity versus a combined exercise and lifestyle intervention on metabolic syndrome in adults with prediabetes: a STRRIDE-PD randomized trial

The purpose of this secondary analysis was to determine what portion of the effects of a Diabetes Prevention Program-like intervention on metabolic syndrome (MetS) could be achieved with exercise alone, as well as to determine the relative importance of exercise intensity and amount to the total exercise effect on MetS. Sedentary, overweight adults with prediabetes were randomly assigned to one of four 6-month interventions: 1) low-amount/moderate-intensity (10 kcal/kg/week at 50% peak V˙O2); 2) high-amount/moderate-intensity (16 kcal/kg/week at 50% peak V˙O2); 3) high-amount/vigorous-intensity (16 kcal/kg/week at 75% peak V˙O2); or 4) diet (7% weight loss) plus low-amount/moderate-intensity (10 kcal/kg/week at 50% peak V˙O2). The primary outcome of this secondary analysis was change in the MetS z-score. A total of 130 participants had complete data for all five Adult Treatment Panel (ATP) III MetS criteria. The diet-and-exercise group statistically outperformed the MetS z-score and the ATP III score compared to the exercise alone group. Aerobic exercise alone achieved 24%–50% of the total effect of the combined diet-and-exercise intervention on the MetS score. Low-amount moderate-intensity exercise quantitatively performed equal to or better than the interventions of high-amount moderate-intensity or high-amount vigorous-intensity exercise in improving the MetS score. The combined diet-and-exercise intervention remains more efficacious in improving the MetS z-score. However, all three exercise interventions alone showed improvements in the MetS z-score, suggesting that a modest amount of moderate-intensity exercise is all that is required to achieve approximately half the effect of a diet-and-exercise intervention on the MetS.Clinical Trial Registration:clinicaltrials.gov, identifier NCT00962962