Long-term CRT has beneficial effects on LV function and myocardial efficiency at rest in patients with HF. These effects are not associated with changes in myocardial perfusion or oxygen consumption. During dobutamine-induced stress, CRT does not affect functional parameters, but myocardial efficiency and metabolic reserve may be increased.

Exercise training improves exercise tolerance and LV function. This is accompanied by a decrease in biventricular oxidative metabolism and enhanced forward work efficiency. Therefore, exercise training elicits an energetically favorable improvement in myocardial function and exercise tolerance in patients with DCM.

The purpose of this study was to examine overall, leg and chest ratings of perceived exertion (RPE) at ventilatory threshold (Thvent) in 16 children (mean age 10.9 years) and 17 adults (mean age 24.3 years). Thvent and maximum oxygen consumption (VO2max) were measured during a graded exercise test on a cycle ergometer. Overall, leg and chest RPE were obtained at the end of each exercise stage. VO2max was 49.9 (8.5) and 47.1 (6.1) ml x kg(-1) x min(-1) [mean (SD)] in the adults and children, respectively (P > 0.05). Relative to VO2max, Thvent was 61.7 (5.3)% in the adults and 64.7 (5.2)% in the children (P > 0.05). Overall, leg, and chest RPE values at Thvent for the adults were 11.5 (2.6), 11.9 (2.5), and 10.5 (2.5), while for the children these values were 13.6 (2.2), 14.1 (2.2), and 12.6 (2.3), respectively. All RPE values were higher for the children (P < 0.05). These results suggest that children are able to discriminate levels of exertion in different parts of their body during graded exercise. Furthermore, children rate an intensity corresponding to Thvent to require a greater overall, leg and chest effort than adults exercising at a similar intensity. This indicates that children experience more pronounced cardiorespiratory and muscular sensations during this type of exercise.

We investigated whether insulin resistance in patients with chronic heart failure (CHF) is associated with impaired insulin signalling in skeletal muscle and whether exercise training would lead to an improvement in insulin signalling, concomitant with enhanced insulin action. Fourteen men with CHF due to idiopathic dilated cardiomyopathy, with mild‐to‐moderate limitation of physical activity and a left‐ventricular ejection fraction of less than 45 %, were studied before and after either a 5 month exercise training programme (n= 7) or standard care (n= 7). Seven healthy men participated as controls. Whole‐body insulin‐stimulated glucose uptake was determined by the euglycaemic hyperinsulinaemic clamp technique and skeletal muscle biopsy samples were obtained before and after the insulin infusion for insulin signalling measurements. Insulin‐stimulated glucose uptake was 20 % lower in CHF patients versus healthy subjects. Physiological hyperinsulinaemia increased tyrosine phosphorylation of insulin receptor substrate (IRS)‐1 by ≈2.5‐fold, IRS‐1‐associated phosphatidylinositol 3‐kinase (PI‐3‐kinase) activity by ≈2‐fold and Akt (protein kinase B) phosphorylation by ≈3‐fold, with similar responses between healthy subjects and CHF patients. Insulin‐mediated glucose uptake was not altered in patients after standard care, whereas exercise training elicited a 25 % increase in glucose uptake. Neither standard care nor exercise training altered insulin‐stimulated tyrosine phosphorylation of IRS‐1, IRS‐1‐associated PI‐3‐kinase activity or Akt phosphorylation. In conclusion, the CHF patients demonstrated impaired insulin‐stimulated glucose uptake, despite normal signal transduction in skeletal muscle at the level of IRS‐1, PI‐3‐kinase and Akt. Of clinical relevance is the finding that exercise training improves glucose uptake. However, these changes in insulin action after exercise training appear to be independent of enhanced insulin signalling at the level of IRS‐1, PI‐3‐kinase or Akt.