Ic syndrome. Methods: Twenty-seven middle-aged obese women (mean ± SD; age = 51 ± 9yr and body mass index = 34 ± 6 kg·m−2) with the metabolic syndrome completed one of three 16-wk aerobic exercise interventions: (i) no-exercise training (Control): seven participants maintained their existing levels of physical activity; (ii) low-intensity exercise training (LIET): 11 participants exercised 5 d·wk−1 at an intensity ≤ lactate threshold (LT); and (iii) high-intensity exercise training (HIET): nineparticipants exercised 3 d·wk−1 at an intensity > LT and 2 d·wk−1 ≤ LT. Exercise time was adjusted to maintain caloric expenditure (400 kcal per session). Single-slice computed tomography scans obtained at the L4-L5 disc space and midthigh were used to determine abdominal fat and thigh muscle cross-sectional areas. Percent body fat was assessed by air displacement plethysmography. Results: HIET significantly reduced total abdominal fat (P < 0.001), abdominal subcutaneous fat (P = 0.034), and AVF (P = 0.010). There were no significant changes observed in any of these parameters within the Control or the LIET conditions. Conclusions: The present data indicate that body composition changes are affected by the intensity of exercise training with HIET more effectively for reducing total abdominal fat, subcutaneous abdominal fat, and AVF in obese women with the metabolic syndrome....

There is evidence from human twin and family studies as well as mouse and rat selection experiments that there are considerable interindividual differences in the response of cardiorespiratory fitness (CRF) and other cardiometabolic traits to a given exercise programme dose. We developed this consensus statement on exercise response variability following a symposium dedicated to this topic. There is strong evidence from both animal and human studies that exercise training doses lead to variable responses. A genetic component contributes to exercise training response variability. In this consensus statement, we (1) briefly review the literature on exercise response variability and the various sources of variations in CRF response to an exercise programme, (2) introduce the key research designs and corresponding statistical models with an emphasis on randomised controlled designs with or without multiple pretests and post-tests, crossover designs and repeated measures designs, (3) discuss advantages and disadvantages of multiple methods of categorising exercise response levels—a topic that is of particular interest for personalised exercise medicine and (4) outline approaches that may identify determinants and modifiers of CRF exercise response. We also summarise gaps in knowledge and recommend future research to better understand exercise response variability.

OBJECTIVE: Reductions in insulin sensitivity in conjunction with muscle mitochondrial dysfunction have been reported to occur in many conditions including aging. The objective was to determine whether insulin resistance and mitochondrial dysfunction are directly related to chronological age or are related to age-related changes in body composition. RESEARCH DESIGN AND METHODS: Twelve young lean, 12 young obese, 12 elderly lean, and 12 elderly obese sedentary adults were studied. Insulin sensitivity was measured by a hyperinsulinemic-euglycemic clamp, and skeletal muscle mitochondrial ATP production rates (MAPRs) were measured in freshly isolated mitochondria obtained from vastus lateralis biopsy samples using the luciferase reaction. RESULTS: Obese participants, independent of age, had reduced insulin sensitivity based on lower rates of glucose infusion during a hyperinsulinemic-euglycemic clamp. In contrast, age had no independent effect on insulin sensitivity. However, the elderly participants had lower muscle MAPRs than the young participants, independent of obesity. Elderly participants also had higher levels inflammatory cytokines and total adiponectin. In addition, higher muscle MAPRs were also noted in men than in women, whereas glucose infusion rates were higher in women. CONCLUSIONS: The results demonstrate that age-related reductions in insulin sensitivity are likely due to an age-related increase in adiposity rather than a consequence of advanced chronological age. The results also indicate that an age-related decrease in muscle mitochondrial function is neither related to adiposity nor insulin sensitivity. Of interest, a higher mitochondrial ATP production capacity was noted in the men, whereas the women were more insulin sensitive, demonstrating further dissociation between insulin sensitivity and muscle mitochondrial function.

Diminished bioavailability of nitric oxide (NO), the gaseous signaling molecule involved in the regulation of numerous vital biological functions, contributes to the development and progression of multiple age- and lifestyle-related diseases. While l-arginine is the precursor for the synthesis of NO by endothelial-nitric oxide synthase (eNOS), oral l-arginine supplementation is largely ineffective at increasing NO synthesis and/or bioavailability for a variety of reasons. l-citrulline, found in high concentrations in watermelon, is a neutral alpha-amino acid formed by enzymes in the mitochondria that also serves as a substrate for recycling l-arginine. Unlike l-arginine, l-citrulline is not quantitatively extracted from the gastrointestinal tract (i.e., enterocytes) or liver and its supplementation is therefore more effective at increasing l-arginine levels and NO synthesis. Supplementation with l-citrulline has shown promise as a blood pressure lowering intervention (both resting and stress-induced) in adults with pre-/hypertension, with pre-clinical (animal) evidence for atherogenic-endothelial protection. Preliminary evidence is also available for l-citrulline-induced benefits to muscle and metabolic health (via vascular and non-vascular pathways) in susceptible/older populations. In this review, we examine the impact of supplementing this important urea cycle intermediate on cardiovascular and metabolic health outcomes and identify future directions for investigating its therapeutic impact on cardiometabolic health.