The exercise pressor reflex (a peripheral neural reflex originating in skeletal muscle) contributes significantly to the regulation of the cardiovascular system during exercise. Exerciseinduced signals that comprise the afferent arm of the reflex are generated by activation of mechanically (muscle mechanoreflex) and chemically sensitive (muscle metaboreflex) skeletal muscle receptors. Activation of these receptors and their associated afferent fibres reflexively adjusts sympathetic and parasympathetic nerve activity during exercise. In heart failure, the cardiovascular response to exercise is augmented. Owing to the peripheral skeletal myopathy that develops in heart failure (e.g. muscle atrophy, decreased peripheral blood flow, fibre-type transformation and reduced oxidative capacity), the exercise pressor reflex has been implicated as a possible mechanism by which the cardiovascular response to physical activity is exaggerated in this disease. Accumulating evidence supports this conclusion. This review therefore focuses on the role of the exercise pressor reflex in regulating the cardiovascular system during exercise in both health and disease. Updates on our current understanding of the exercise pressor reflex neural pathway as well as experimental models used to study this reflex are presented. In addition, special emphasis is placed on the changes in exercise pressor reflex activity that develop in heart failure, including the contributions of the muscle mechanoreflex and metaboreflex to this pressor reflex dysfunction.
Blood flow restriction (BFR) training (also known as Kaatsu training) is an increasingly common practice employed during resistance exercise by athletes attempting to enhance skeletal muscle mass and strength. During BFR training, blood flow to the exercising muscle is mechanically restricted by placing flexible pressurizing cuffs around the active limb proximal to the working muscle. This maneuver results in the accumulation of metabolites (e.g., protons and lactic acid) in the muscle interstitium that increase muscle force and promote muscle growth. Therefore, the premise of BFR training is to simulate and receive the benefits of high-intensity resistance exercise while merely performing low-intensity resistance exercise. This technique has also been purported to provide health benefits to the elderly, individuals recovering from joint injuries, and patients undergoing cardiac rehabilitation. Since the seminal work of Alam and Smirk in the 1930s, it has been well established that reductions in blood flow to exercising muscle engage the exercise pressor reflex (EPR), a reflex that significantly contributes to the autonomic cardiovascular response to exercise. However, the EPR and its likely contribution to the BFR-mediated cardiovascular response to exercise is glaringly missing from the scientific literature. Inasmuch as the EPR has been shown to generate exaggerated increases in sympathetic nerve activity in disease states such as hypertension (HTN), heart failure (HF), and peripheral artery disease (PAD), concerns are raised that BFR training can be used safely for the rehabilitation of patients with cardiovascular disease, as has been suggested. Abnormal BFR-induced and EPR-mediated cardiovascular complications generated during exercise could precipitate adverse cardiovascular or cerebrovascular events (e.g., cardiac arrhythmia, myocardial infarction, stroke and sudden cardiac death). Moreover, although altered EPR function in HTN, HF, and PAD underlies our concern for the widespread implementation of BFR, use of this training mechanism may also have negative consequences in the absence of disease. That is, even normal, healthy individuals performing resistance training exercise with BFR are potentially at increased risk for deleterious cardiovascular events. This review provides a brief yet detailed overview of the mechanisms underlying the autonomic cardiovascular response to exercise with BFR. A more complete understanding of the consequences of BFR training is needed before this technique is passively explored by the layman athlete or prescribed by a health care professional.
Recent government initiatives to deploy health information technology in the USA, coupled with a growing body of scholarly evidence linking online heath information and positive health-related behaviors, indicate a widespread belief that access to health information and health information technologies can help reduce healthcare inequalities. However, it is less clear whether the benefits of greater access to online health information and health information technologies is equitably distributed across population groups, particularly to those who are underserved. To examine this issue, this article employs the 2007 Health Information National Trends Survey (HINTS) to investigate relationships between a variety of socio-economic variables and the use of the web-based technologies for health information seeking, personal health information management and patient-provider communication within the context of the USA. This study reveals interesting patterns in technology adoption, some of which are in line with previous studies, while others are less clear. Whether these patterns indicate early evidence of a narrowing divide in eHealth technology use across population groups as a result of the narrowing divide in Internet access and computer ownership warrants further exploration. In particular, the findings emphasize the need to explore differences in the use of eHealth tools by medically underserved and disadvantaged groups. In so doing, it will be important to explore other psychosocial variables, such as health literacy, that may be better predictors of health consumers' eHealth technology adoption.
1. The purpose of this investigation was to determine if activation of the exercise pressor reflex in the decerebrate rat induced circulatory responses comparable to those reported in large mammalian species. 2. To activate both mechanically and metabolically sensitive afferent fibres, static hindlimb contractions were induced by stimulating the cut ends of L4 and L5 spinal ventral roots in Sprague-Dawley rats (300-400 g). To selectively stimulate mechanically sensitive receptors, hindlimb muscles were passively stretched. 3. In intact halothane-anaesthetized animals (n = 10), static contraction and passive stretch induced a decrease in mean arterial pressure (Delta MAP = -17 +/- 3 and -8 +/- 1 mmHg for contraction and stretch, respectively) and heart rate (HR). In contrast, MAP increased 23 +/- 2 mmHg during contraction and 19 +/- 3 mmHg during stretch in decerebrate rats (n = 10). These pressor responses were accompanied by a significant tachycardia. In decerebrate animals, the reintroduction of halothane attenuated the increase in MAP and HR caused by both contraction and stretch. 4. In both anaesthetized and decerebrate rats, sectioning the spinal dorsal roots innervating the activated skeletal muscle eliminated responses to contraction and stretch. This finding indicated that an intramuscular neural reflex mediated the response to each stimulus. 5. The results demonstrate that a decerebrate preparation in the rat is a reliable model for the study of the exercise pressor reflex. Development of the model would enable the study of this reflex in a variety of pathological conditions and allow investigation of the mechanisms controlling cardiovascular responses to exercise in health and disease.
Background The Consumer Assessment of Healthcare Providers and Systems (CAHPSR) Clinician and Group Adult Visit Survey enables patients to report their experiences with outpatient medical offices. Objective To evaluate the factor structure and reliability of the CAHPS Clinician and Group (CG-CAHPS) Adult Visit Survey. Data Source Data from 21,318 patients receiving care in 450 clinical practice sites collected from March 2010 to December 2010 were analyzed from the CG-CAHPS Database. Research Design and Participants Individual level and multilevel confirmatory factor analyses were used to examine CAHPS survey responses at the patient and practice site levels. We also estimated internal consistency reliability and practice site level reliability. Correlations among multi-item composites and correlations between the composites and two global rating items were examined. Measures Scores on CG-CAHPS composites assessing Access to Care, Doctor Communication, Courteous/Helpful Staff, and two global ratings of whether one would Recommend their Doctor, and an Overall Doctor Rating. Results Analyses provide support for the hypothesized three-factor model assessing Access to Care, Doctor Communication, and Courteous/Helpful Staff. In addition, the internal consistency reliabilities were 0.77 or higher and practice site level reliabilities for sites with more than four clinicians were 0.75 or higher. All composites were positively and significantly correlated with the two global rating items, with Doctor Communication having the strongest relationship with the global ratings. Conclusions The CG-CAHPS Adult Visit Survey has acceptable psychometric properties at the individual level and practice site level. The analyses suggest that the survey items are measuring their intended concepts and yield reliable information.
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