effects of detraining on cardiovascular responses to exercise: role of blood volume edward f. coyle,...
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Effects of detraining on cardiovascular responses to exercise: role of blood volumeEDWARD F. COYLE, MAR1 K. HEMMERT, AND ANDREW R. COGGANJ. Appl. Physiol. 60(l): 95-99, 1986.Large decline in SV during upright exercise after only 12 days of inactivity and little further decline in SV occurs after 3 mo of inactivity. VO2 max was determined, and cardiac output was measured during upright cycling at 50-60% VO2 max in eight endurance-trained men before and after 2-4 wk of inactivity. Detraining produced a 9% decline in blood volume (5,177 to 4,692). SV was reduced by 12% (P < 0.05) and VO2 max declined 6% (P < 0.01); heart rate (HR) and total peripheral resistance (TPR) during submaximal exercise were increased 11% (P < 0.01) and 8% (P < 0.05). When blood volume was expanded to a similar absolute level (5,500 200 ml) by 6% dextran in saline, the effects of detraining on cardiovascular response were reversed. SV and VO2 max were increased (P < 0.05) by PV expansion in the detrained state to within 2-4% of trained values. Additionally, HR and TPR during submaximal exercise were lowered to near trained values. These findings indicate that the decline in cardiovascular function following a few weeks of detraining is largely due to a reduction in blood volume, which appears tolimit ventricular filling during upright exercise.
Effect of Aerobic Exercise on Blood Pressure: A Meta-Analysis of Randomized, Controlled TrialsSeamus P. Whelton; Ashley Chin, MPH, MA; Xue Xin, MD, MS; and Jiang He, MD, PhDAnn Intern Med. 2002;136:493-503.
This meta-analysis is a comprehensive examination of the effect of aerobic exercise on blood pressure and is based on randomized, controlled clinical trials. Our meta-analysis included 54 clinical trials that involved 2419 participants and were conducted in a wide range of geographic regions and ethnic populations. Our study showed that aerobic exercise has an impressive bloodpressurelowering effect: 3.84 mm Hg for systolic blood pressure and 2.58 mm Hg for diastolic blood pressure. It is important to distinguish between the individual and public health implications of our findings. The blood pressure reduction that we observed may be of moderate interest to practitioners treating individual patients. However, a small decrease in the populations average blood pressure level should dramatically reduce incidence of and death from cardiovascular disease in communities. All forms of exercise seem to be effective in reducing blood pressure. Aerobic exercise reduces insulin resistance and insulin levels in hypertensive patients. Change in blood pressure during exercise is strongly associated with reduction in serum concentrations of total cholesterol and insulin resistance.
Effects of Aging, Sex, and Physical Training on Cardiovascular Responses to ExerciseTakeshi Ogawa, MD; Robert J. Spina, PhD; Wade H. Martin III, MD; Wendy M. Kohrt, PhD;Kenneth B. Schechtman, PhD; John O. Holloszy, MD; and Ali A. Ehsani, MD(Circulation 1992;86:494-503)To investigate the mechanism of the age-related decline in exercise capacity, we measured oxygen uptake, cardiac output, heart rate, and other cardiovascular responses to submaximal and maximal treadmill exercise in healthy sedentary and endurance exercise-trained younger and older men and women. We estimated fat-free mass in the same individuals from measurements of body weight and density. Our findings provide evidence that the decline in VO2max with age is related primarily to a lower maximal cardiac output. Although a slower maximal heart rate accounts for a portion of this effect, a smaller stroke volume is of greater importance. Differences in VO2max between 25- and 65-year-old sedentary subjects of the same sex are approximately 40%. (10% per decade). After normalization of results to fat-free mass, however, VO2max , maximal cardiac output, and stroke volume were an average of 24%, 17%,and 8% lower, respectively, in older than in younger individuals.
The smaller stroke volume observed in older subjects at maximal exercise was associated with a higher mean blood pressure in women and sedentary men. For these groups, stroke work in the older subjects was equal to or greater than that in younger individuals. Stroke volume and cardiac output at maximal exercise were lower in women than in men, even after normalizationto weight. Normalization of results to fat-free mass eliminated the sex difference entirely in sedentary subjects and substantially reduced it in trained individuals. Thus, the sex difference is largely a result of the greater percentage of body fat in women. However, there were sex differences in mechanisms by which exercise capacity was enhanced in conditioned versussedentary subjects. Training status had a larger effect on stroke volume and maximal cardiac output but a smaller effect on maximal arteriovenous oxygen difference in men than in women. Sex differences in the nature and magnitude of adaptations to training were particularly evident in older subjects.
Exercise as Cardiovascular TherapyRoy J. Shephard, MD, PhD, DPE; Gary J. Balady, MDCirculation 1999;99;963-972Possible Biological Mechanisms for Exercise-Induced Reductions in All-Cause and Cardiac MortalityCardiovascular influencesReduction of resting and exercise heart rateReduction of resting and exercise blood pressureReduction of myocardial oxygen demand at submaximal levels of physical activityExpansion of plasma volumeIncrease in myocardial contractilityIncrease in peripheral venous toneFavorable changes in fibrinolytic systemIncreased endothelium-dependent vasodilatationIncreased gene expression for nitric oxide synthaseEnhanced parasympathetic tonePossible increases in coronary blood flow, coronary collateral vessels, and myocardial capillary density
Metabolic influencesReduction of obesityEnhanced glucose toleranceImproved lipid profile
Lifestyle influencesDecreased likelihood of smokingPossible reduction of stressShort-term reduction of appetite
Does Exercise Reduce Inflammation? Physical Activity and C-Reactive ProteinAmong U.S. AdultsEarl S. FordEPIDEMIOLOGY September 2002, Vol. 13 No. 5
In conclusion, the results of this study showed that physical activity is inversely associated with C-reactive protein concentrations, suggesting that physical activity may mitigate inflammation. Research to delineate the exact mechanisms through which physical activity influencesthe inflammatory process will help improve our understanding of some of the benefits of physical activity.Furthermore, additional research concerning the relation of the intensity, duration, and type of physical activity with inflammation could yield additional insights into how physical activity might influence inflammation.
The anti-inflammatory effect of exercise: its role in diabetes and cardiovascular disease controlBente Klarlund Pedersen1Essays in Biochemistry volume 42 2006
Role of inflammation in the pathogenesis of atherosclerosis. Further, inflammationhas been suggested to be a key factor in insulin resistanceRecent findings demonstrate that physical activity induces an increase in the systemic levels of a number of cytokines with anti-inflammatory propertiesGiven that skeletal muscle is the largest organ in the human body, the discovery that contracting muscle is a cytokine producing organ opens a new paradigm: skeletal muscle is an endocrine organ that by contraction stimulates the production and release of cytokines, which can influence metabolism and modify cytokine production in tissue and organsThe evidence for a beneficial effect of physical training in patients with coronary heart disease is strong. Few studies have examined the isolated effect of training on the prevention of diabetes in patients with impaired glucose tolerance, but there is good evidence for a beneficial effect of combined physical training and dietary modification
The beneficial effect of training in patients with type 2 diabetes is very well documented, and there is international consensus that physical training comprises one of the three cornerstones of the treatment of diabetes together with diet and medicine.The players in chronic low-grade inflammation and its link with chronic diseasesThe local inflammatory response is accompanied by a systemic response known as the acute phase response. This response includes the production of a large number of hepatocyte-derived acute phase proteins, such as CRP and can be mimicked by the injection of cytokines. Chronic low-grade systemic inflammation has been introduced as a term for conditions in which a 2- to 3-fold increase in the systemic concentrations of TNF-, IL-1, IL-6, IL-1ra, sTNF-R and CRP is reflected; TNF- derives mainly from the adipose tissue
The link between inflammation, insulin resistance and atherosclerosisAgeing is associated with increased resting plasma levels of TNF- , IL-6, IL-1ra, sTNF-R and CRP. High levels of TNF- are associated with dementia and atherosclerosis. Also, elevated levels of circulating IL-6 are associated with several disorders. Increased levels of both TNF- and IL-6are observed in obese individuals, in smokers and in patients with type 2 diabetes mellitus. Plasma concentrations of IL-6 have been shown to predict all-cause mortality as well as cardiovascular mortality. Furthermore, plasma concentrations of IL-6 and TNF- have been shown to predict the risk of myocardial infarction in several studies, and the CRP level is shown to be a stronger predictor of cardiovascular events than the low density lipoprotein cholesterol level.
Mounting evidence suggests that TNF- plays a direct role in the metabolic syndrome. Accumulating data suggest that IL-6 enhances glucose uptake in myocytes. A number of studies indicate that IL-6 enhances lipolysi