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001, time effect P http://www.selleckchem.com/products/lee011.html to poor exercise tolerance in HF. This study demonstrates that in patients with HF, CRT significantly decreased MSNA at rest and during static exercise. To the best of our knowledge, this is the first study to show the effects of CRT in MSNA during isometric exercise, a condition in which central command and exercise pressor reflex (EPR), for example, metaboreflex and mechanoreflex, http://www.selleck.cn/products/AZD6244.html are simultaneously activated. Besides this functional behavior, we observed that CRT improves exercise capacity as measured by peak VO2 and NYHA functional class, which is in accordance with findings of prior randomized clinical trials.[2-10] However, the mechanisms of this benefit are not well understood. Therefore, we consider that CRT effects on limb neurovascular control may contribute to a better understanding of this issue. Although exercise intolerance is a hallmark of HF, the mechanisms of the symptoms are not completely understood. Evidence from the literature has shown that peripheral hemodynamic variables and skeletal muscles abnormalities, rather than ejection fraction and intracardiac hemodynamic alterations, seem to play an important role in exercise intolerance in patients with HF.[23-27] Moreover, previous studies including randomized controlled trials have shown that CRT improves peak VO2 without significant changes in systolic function.[6, 7] These findings are in accordance with the muscle hypothesis proposed by Coats et al.[28] in the early 1990s. In that paper, the authors suggested that exercise intolerance in HF patients is caused by increased ergoreflex activity (i.e., somatic afferents located in skeletal muscle sensitive to metabolic by-products), hyperventilation, increased sympathetic nerve activity, and peripheral vasoconstriction. The concept that muscle mechanoreceptor http://www.selleckchem.com/products/bmn-673.html sensitivity is increased in HF was postulated by several investigators after observing that the muscle metaboreflex is blunted in HF patients.[29, 30] Prior evidence suggests that this is the predominant mechanism leading to sympathetic activity observed in HF patients during exercise. Middlekauff et al.[31] demonstrated that MSNA increases during low-level rhythmic handgrip exercise in the first minute in HF patients and only in the third minute of exercise in healthy control individuals. These results confirm that muscle mechanoreceptor control is augmented in patients with HF.