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PubMed2005

Exercise training in obese children and adolescents: current concepts.

Childhood obesity has reached epidemic proportions worldwide and is associated with increased cardiovascular mortality and morbidity in adult life. The increase in fat mass in children and adolescents has occurred concomitantly with a decline in reported time for exercise. Evidence suggests that non-physically active children are more likely to become non-physically active adults and that encouraging the development of physical activity habits in children helps establish patterns that continue into adulthood. Dietary treatment of obesity is relatively ineffective in adults and it has been suggested that prevention of obesity in childhood and adolescence should emphasise increased physical activity rather than diet because of fears relating to the adverse effects of inappropriate eating patterns. Despite this, there are very few randomised controlled studies investigating the efficacy of exercise training in obese children or adolescents and many of the extant studies have been poorly controlled and have not specifically stratified the independent effect of exercise versus dietary modification. This review focuses on the well designed controlled trials that have evaluated the effect of exercise training in obese children and adolescents on body composition, haemodynamic and metabolic variables, cardiovascular fitness, muscular strength and vascular function. These studies indicate that, although exercise training does not consistently decrease bodyweight or body mass index, it is associated with beneficial changes in fat and lean body mass, emphasising the importance of comprehensive assessment of body composition in future exercise-training studies. Exercise training improves cardiovascular fitness and muscular strength; however, it seems to have little effect on blood lipid profile or blood pressure in obese young people. Importantly, recent studies have demonstrated that exercise training improves vascular endothelial function, an important surrogate measure that may predict future atherosclerotic risk in obese children and adolescents. Given that improvement in vascular function in these training studies occurred in the absence of changes in lipid fractions, haemodynamic variables or glucose metabolism, exercise appears to have a direct beneficial effect on the vasculature, in addition to its putative benefits through risk-factor modification.

Adolescent↗

PubMed2002

Changes in high-density lipoprotein-cholesterol subfractions with exercise training may be dependent on cholesteryl ester transfer protein (CETP) genotype.

We sought to determine if a cholesteryl ester transfer protein (CETP) gene locus variation contributes to the variability in the responses of plasma high-density lipoprotein-cholesterol (HDL-C) and its subfractions to endurance exercise training. Middle- to older-aged men and women with at least 1 lipoprotein-lipid risk factor underwent 6 months of endurance exercise training while on a low-fat diet. Plasma lipid levels were measured by nuclear magnetic resonance (NMR). Initial age, body composition, lipoprotein-lipid profiles, and VO(2)max did not differ between the 2 CETP genotype groups (B1B1, n = 16; B1B2, n = 14). With exercise training, VO(2)max increased, and body weight, total body fat, and computed tomographic (CT) intra-abdominal visceral fat decreased similarly in both CETP genotype groups. Plasma total cholesterol and low-density lipoprotein-cholesterol (LDL-C) levels did not change significantly with training in either genotype group. HDL(2NMR)-C levels increased with exercise training in CETP B1B1 (P <.05), but did not change in CETP B1B2 genotype individuals. HDL(3NMR)-C levels tended to decrease with training in CETP B1B1 persons and HDL(4NMR)-C levels tended to increase with training somewhat more in CETP B1B2 individuals, but these differences were not significant. HDL(5NMR)-C levels increased similarly with exercise training in the 2 groups. The integrated HDL(3-5NMR)-C levels increased with exercise training in CETP B1B2 (P <.05), but did not change in CETP B1B1 genotype individuals. Apolipoprotein E (APO E) or lipoprotein lipase (LPL) PvuII genotype did not associate with HDL-C subfraction changes with training. Thus, CETP genotype may contribute to the interindividual differences in plasma HDL-C subfraction changes occurring with endurance exercise training in sedentary middle- to older-aged men and women.

Apolipoproteins E↗

PubMed2002

Exercise training improves muscle insulin resistance but not insulin receptor signaling in obese Zucker rats.

Exercise training improves skeletal muscle insulin sensitivity in the obese Zucker rat. The purpose of this study was to investigate whether the improvement in insulin action in response to exercise training is associated with enhanced insulin receptor signaling. Obese Zucker rats were trained for 7 wk and studied by using the hindlimb-perfusion technique 24 h, 96 h, or 7 days after their last exercise training bout. Insulin-stimulated glucose uptake (traced with 2-deoxyglucose) was significantly reduced in untrained obese Zucker rats compared with lean controls (2.2 +/- 0.17 vs. 5.4 +/- 0.46 micromol x g(-1) x h(-1)). Glucose uptake was normalized 24 h after the last exercise bout (4.9 +/- 0.41 micromol x g(-1) x h(-1)) and remained significantly elevated above the untrained obese Zucker rats for 7 days. However, exercise training did not increase insulin receptor or insulin receptor substrate-1 (IRS-1) tyrosine phosphorylation, phosphatidylinositol 3-kinase (PI3-kinase) activity associated with IRS-1 or tyrosine phosphorylated immunoprecipitates, or Akt serine phosphorylation. These results are consistent with the hypothesis that, in obese Zucker rats, adaptations occur during training that lead to improved insulin-stimulated muscle glucose uptake without affecting insulin receptor signaling through the PI3-kinase pathway.

Animals↗

PubMed2006

Exercise training improves aortic depressor nerve sensitivity in rats with ischemia-induced heart failure.

Exercise training improves arterial baroreflex control in heart failure (HF) rabbits. However, the mechanisms involved in the amelioration of baroreflex control are unknown. We tested the hypothesis that exercise training would increase the afferent aortic depressor nerve activity (AODN) sensitivity in ischemic-induced HF rats. Twenty ischemic-induced HF rats were divided into trained (n = 11) and untrained (n = 9) groups. Nine normal control rats were also studied. Power spectral analysis of pulse interval, systolic blood pressure, renal sympathetic nerve activity (RSNA), and AODN were analyzed by means of autoregressive parametric spectral and cross-spectral algorithms. Spontaneous baroreflex sensitivity of heart rate (HR) and RSNA were analyzed during spontaneous variation of systolic blood pressure. Left ventricular end-diastolic pressure was higher in HF rats compared with that in the normal control group (P = 0.0001). Trained HF rats had a peak oxygen uptake higher than untrained rats and similar to normal controls (P = 0.01). Trained HF rats had lower low-frequency [1.8 +/- 0.2 vs. 14.6 +/- 3 normalized units (nu), P = 0.0003] and higher high-frequency (97.9 +/- 0.2 vs. 85.0 +/- 3 nu, P = 0.0005) components of pulse interval than untrained rats. Trained HF rats had higher spontaneous baroreceptor sensitivity of HR (1.19 +/- 0.2 vs. 0.51 +/- 0.1 ms/mmHg, P = 0.003) and RSNA [2.69 +/- 0.4 vs. 1.29 +/- 0.3 arbitrary units (au)/mmHg, P = 0.04] than untrained rats. In HF rats, exercise training increased spontaneous AODN sensitivity toward normal levels (trained HF rats, 1,791 +/- 215; untrained HF rats, 1,150 +/- 158; and normal control rats, 2,064 +/- 327 au/mmHg, P = 0.05). In conclusion, exercise training improves AODN sensitivity in HF rats.

Algorithms↗

PubMed1995

Effect of exercise training on antioxidant system in brain regions of rat.

The purpose of this investigation was to determine whether any alterations in antioxidant enzyme activities and levels of glutathione (GSH) in brain regions occurred following exercise training. Sprague-Dawley rats were given exercise training on a treadmill for 7.5 weeks and sacrificed 18 h after the last exercise along with the sedentary control rats. Different brain regions-cerebral cortex (CC), brainstem (BS), corpus striatum (CS), and hippocampus (H)-were isolated; GSH, oxidized glutathione (GSSG), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities were determined. The exercise training increased SOD activity significantly (130% of sedentary control) in BS and in CS. SOD activity in H was the lowest of all four brain regions. Different brain regions showed GSH-Px activity in decreasing order for CS < BS < CC < H. GSH levels were 43% less in BS than CC and CS. The ratio of GSH/GSSG significantly increased from 6.8 to 8.3 in CC, and from 9.4 to 13.5 in BS as a result of exercise training. Different brain regions contained different activities of antioxidant enzymes, as well as GSH and GSSG levels, which were preferentially altered as a result of exercise training to cope with oxidative stress.

Adaptation, Physiological↗

PubMed2004

Exercise training changes autonomic cardiovascular balance in mice.

Experiments were performed to investigate the influence of exercise training on cardiovascular function in mice. Heart rate, arterial pressure, baroreflex sensitivity, and autonomic control of heart rate were measured in conscious, unrestrained male C57/6J sedentary (n = 8) and trained mice (n = 8). The exercise training protocol used a treadmill (1 h/day; 5 days/wk for 4 wk). Baroreflex sensitivity was evaluated by the tachycardic and bradycardic responses induced by sodium nitroprusside and phenylephrine, respectively. Autonomic control of heart rate and intrinsic heart rate were determined by use of methylatropine and propranolol. Resting bradycardia was observed in trained mice compared with sedentary animals [485 +/- 9 vs. 612 +/- 5 beats/min (bpm)], whereas mean arterial pressure was not different between the groups (106 +/- 2 vs. 108 +/- 3 mmHg). Baroreflex-mediated tachycardia was significantly enhanced in the trained group (6.97 +/- 0.97 vs. 1.6 +/- 0.21 bpm/mmHg, trained vs. sedentary), whereas baroreflex-mediated bradycardia was not altered by training. The tachycardia induced by methylatropine was significantly increased in trained animals (139 +/- 12 vs. 40 +/- 9 bpm, trained vs. sedentary), whereas the propranolol effect was significantly reduced in the trained group (49 +/- 11 vs. 97 +/- 11 bpm, trained vs. sedentary). Intrinsic heart rate was similar between groups. In conclusion, dynamic exercise training in mice induced a resting bradycardia and an improvement in baroreflex-mediated tachycardia. These changes are likely related to an increased vagal and decreased sympathetic tone, similar to the exercise response observed in humans.

Animals↗

PubMed1998

Effect of exercise training and food restriction on endothelium-dependent relaxation in the Otsuka Long-Evans Tokushima Fatty rat, a model of spontaneous NIDDM.

We investigated whether endothelial function may be impaired in the Otsuka Long-Evans Tokushima Fatty (OLETF) rat, a model of spontaneous NIDDM. The effect of exercise training and food restriction on endothelial function was also studied. OLETF rats were divided into three groups at age 16 weeks: sedentary, exercise trained, and food restricted (70% of the food intake of sedentary rats). Otsuka Long-Evans Tokushima rats were used as the age-matched nondiabetic controls. Endothelium-dependent relaxation of the thoracic aorta induced by histamine was significantly attenuated in the sedentary or food-restricted rats, and exercise training improved endothelial function. Relaxation induced by sodium nitroprusside, a donor of nitric oxide, did not differ significantly among groups. Both exercise training and food restriction significantly suppressed plasma levels of glucose and insulin and serum levels of triacylglycerol and cholesterol and reduced the accumulation of abdominal fat. Insulin sensitivity, as measured by the hyperinsulinemic-euglycemic clamp technique, was significantly decreased in sedentary rats but was enhanced in exercise-trained and food-restricted rats. The urinary excretion of nitrite was significantly decreased in sedentary and food-restricted rats compared with nondiabetic rats and was significantly increased in exercise-trained rats. These results indicate that exercise training, but not food restriction, prevents endothelial dysfunction in NIDDM rats, presumably due to the exercise-induced increase in the production of nitric oxide.

Abdomen↗

PubMed1997

Randomized trial of a hospital-based exercise training program after acute myocardial infarction: cardiac autonomic effects.

OBJECTIVES: This study sought to determine whether a moderate intensity supervised exercise training program, performed immediately after an uncomplicated acute myocardial infarction, improves recovery in cardiac autonomic function compared with standard advice about activity at home. BACKGROUND: Exercise training has beneficial effects on cardiac autonomic function and may improve prognosis after acute myocardial infarction. METHODS: Thirty-nine male and 10 female patients, mean (+/-SE) age 57 +/- 1 years, with an uncomplicated acute myocardial infarction were randomized to either a 6-week moderate intensity supervised hospital-based exercise training program (exercise group) or to an unsupervised low intensity home walking program (control group). Outcome measures included changes in baroreflex sensitivity (phenylephrine bolus method) and heart rate variability (24-h Holter monitoring) and the endurance time at 85% of peak oxygen consumption. RESULTS: At baseline, there were no significant differences in left ventricular ejection fraction (57 +/- 2% vs. 53 +/- 2%), frequency of anterior infarction (27% vs. 18%) and peak creatine kinase (1,256 +/- 170 vs. 2,599 +/- 295 IU) between the exercise and control groups. Baroreflex sensitivity (10.5 +/- 1.0 vs. 8.4 +/- 1.2 ms/mm Hg) and time domain measures of heart rate variability were also similar. After completion of the program, the exercise group exercised for a median of 15 min (interquartile range 12 to 25) at a workload of 104 +/- 7 W compared with 7 min (interquartile range 3.5 to 12) at a workload of 89 +/- 8 W in the control group (p < 0.01). There were significant (p < 0.001) improvements in baroreflex sensitivity and heart rate variability for the 49 patients combined but no differences between the exercise and control groups. Baroreflex sensitivity improved by 3.4 +/- 1.0 and 1.7 +/- 1.0 ms/mm Hg and the standard deviation of 24-h RR intervals by 36 +/- 6 and 40 +/- 10 ms, respectively (p > 0.1). CONCLUSIONS: A hospital-based exercise training program increased endurance capacity but did not improve recovery of cardiovascular antonomic function after uncomplicated acute myocardial infarction.

Ambulatory Care↗

PubMed1998

Increased orthostatic tolerance following moderate exercise training in patients with unexplained syncope.

OBJECTIVE: To determine whether a programme of simple, moderate exercise training increases blood volume and improves orthostatic tolerance in patients with attacks of syncope or near syncope related to orthostatic stress. DESIGN: An open study in 14 patients referred with unexplained attacks of syncope, who were shown to have a low tolerance to an orthostatic stress test. Measurements were made of plasma and blood volumes, orthostatic tolerance to a test of combined head up tilt and lower body suction, and baroreceptor sensitivity by applying subatmospheric pressures to a chamber over the neck. Cardiorespiratory fitness was assessed from the relation between heart rate and oxygen uptake during a graded treadmill exercise test. Assessments were made before and after undertaking an exercise training programme (Canadian Air Force 5BX/XBX). RESULTS: After the training period, 12 of the 14 patients showed evidence of improved cardiorespiratory fitness. All 12 patients were symptomatically improved; they showed increases in plasma and blood volumes and in orthostatic tolerance, and decreases in baroreceptor sensitivity. Despite the improved orthostatic tolerance, values of blood pressure both while supine and initially following tilting were lower than before training. CONCLUSIONS: Exercise training has a role in the management of patients with syncope and poor orthostatic tolerance. It improves symptoms and increases orthostatic tolerance without increasing resting blood pressure.

Adolescent↗

PubMed2002

Exercise training and the cardiovascular consequences of type 2 diabetes and hypertension: plausible mechanisms for improving cardiovascular health.

The coexistence of type 2 diabetes and hypertension is especially damaging to cardiovascular health. Most trials of exercise training for these conditions have focused on glycemic control and blood pressure reduction. Less is known about the effects of exercise on the cardiovascular consequences of diabetes and hypertension. This article reviews the available evidence and plausible mechanisms by which exercise training may improve the cardiovascular health of persons with type 2 diabetes and hypertension and provides practical guidelines for exercise prescription. A MEDLINE search was performed for January 1985 to June 2002. Bibliographies from relevant articles, professional society clinical practice guidelines, and books were also reviewed. Because few large, randomized trials exist on these topics, meta-analyses, smaller trials, nonrandomized trials, and animal studies were also considered. Data quality was determined by publication in peer-reviewed journals or professional society literature. Type 2 diabetes and hypertension result in abnormalities in central and peripheral parameters of cardiovascular structure and function. Evidence for an exercise training benefit is strongest for improvements in endothelial vasodilator function and left ventricular diastolic function. The data for exercise training's improvement of arterial stiffness and system inflammation and reduction of left ventricular mass are less robust. However, this assertion is based more on a lack of randomized controlled trials rather than data to the contrary. Exercise training also reduces total and abdominal fat. These changes in body composition mediate improvements in insulin sensitivity and blood pressure and may improve endothelial vasodilator function. The current evidence, albeit not fully confirmed in randomized trials, suggests that the benefits of exercise training go beyond the recognized benefits of glycemic control and blood pressure reduction.

Adipose Tissue↗

PubMed1998

How effective is exercise training for the treatment of hypertension?

OBJECTIVE: Exercise is often recommended as therapy for hypertension, yet its use is not widespread among clinicians. Reasons include uncertainty regarding its efficacy, the relative importance of the exercise prescription determinants (intensity and frequency), or confounding variables including patient characteristics such as age and gender. This review will present the evidence for exercise as a treatment for hypertension using a search of the English language literature from January 1966 to January 1998. DATA SOURCES: A search of MEDLINE articles using the MESH headings and textwords of blood pressure, hypertension, exercise, and exertion as well as hand searches in related articles and cross-referencing. DATA EXTRACTION AND SYNTHESIS: Identified articles were reviewed for their design characteristics, and specific attention was made of the subject characteristics, the exercise training protocol, the magnitude of the blood pressure-lowering response, and the influence of pharmacologic treatment on blood pressure lowering. RESULTS: A total of 39 studies representing random and nonrandom designs using predominantly walking-jogging exercise were identified. These studies showed reductions in blood pressure (systolic blood pressure/diastolic blood pressure) of -13/ -18 mm Hg in hypertensive patients. Most of the antihypertensive effect of exercise training was observed after 10 weeks, whereas training more than three times per week or for more than 50 minutes did not confer added benefit. Lower intensity exercise resulted in greater blood pressure reduction than did high intensity exercise. No gender differences in the antihypertensive effect of exercise were observed although most studies were performed in men. Although few studies were performed in older patients, there did not appear to be an age-dependent antihypertensive effect of exercise. There was a paucity of literature regarding the interaction of pharmacologic therapy and exercise in hypertensive patients. CONCLUSIONS: The results support the use of exercise as an effective therapy in hypertension. Studies were generally lacking in adequate control groups. Future research opportunities are many and should include studies using ambulatory monitoring and stratification of patients with different degrees of hypertension, undergoing different pharmacologic regimens.

Clinical Trials as Topic↗

PubMed2003

Effects of exercise training on glomerular structure in fructose-fed spontaneously hypertensive rats.

A high-fructose diet (HFD) has been shown to elevate blood pressure (BP) and to decrease insulin sensitivity in rats. Although running exercise can attenuate these phenomena, its effect on target organ protection is not clear. We investigated whether exercise training has renal protective effects in this model. Nine-week-old spontaneously hypertensive rats were allocated to groups that received HFD or a control diet (control group) for 15 weeks. At the age of 10 weeks, fructose-fed rats were allocated to groups that were given vehicle (FRU group), temocapril, an angiotensin converting enzyme inhibitor (TEM group), exercise training (EX group; treadmill running), or temocapril plus exercise training (TEM+EX group). BP was higher in the FRU group than in the control group. Exercise training tended to decrease BP and temocapril treatment decreased BP significantly. Proteinuria was similar in the five groups. Plasma leptin concentration and epididymal fat weight were lower in the EX and TEM+EX groups than in the FRU group. In the soleus muscle of the FRU group, the composite ratio of type I fiber was decreased and that of type IIa fiber was increased compared with those in the control group. Both temocapril and exercise training restored these ratios. The glomerular sclerosis index (GSI) was higher in the FRU group than in the control group. GSI was decreased equally in the TEM, EX, and TEM+EX groups and was positively correlated with plasma leptin concentration. The results suggest that exercise training ameliorates glomerular sclerosis through mechanisms other than a reduction in BP.

Aging↗

PubMed2003

Effects of exercise training on physical activity in older people: a randomized controlled trial.

BACKGROUND: Recent randomized controlled trials indicated that exercise training for elderly significantly increased their physical fitness. However, very few studies have examined changes in physical activity after exercise training. The purpose of this study was to investigate whether six-month exercise training for older adults can increase and maintain their physical activity in daily life. METHODS: Sixty-two men and women aged 60 to 81 years (mean age 67.1 years), living in communities, were randomly allocated into an exercise group (n = 32) or a control group (n = 33). The intervention started in April 1998 and lasted for 25 weeks. The exercise regimen consisted of endurance training and resistance exercises in a two-hour class conducted at least twice a week. The subjects completed a physical activity diary at each pre-intervention (March 1998), post-intervention (September 1998) and follow-up (April 1999) measurement of physical activity. Physical activity, expressed as total daily energy expenditure, was calculated by multiplying the amount of time spent in each activity and the corresponding METs. RESULTS: Total daily energy expenditure significantly increased from 40.8 kcal/kg/day to 43.5 kcal/kg/day in the exercise group (p = 0.03), but did not change in the control group. At the follow-up measurement, the mean total daily energy expenditure in the exercise group remained significantly higher, by 1.7 kcal/kg/day, than that at the pre-intervention (p = 0.05). CONCLUSIONS: This randomized controlled trial indicated that exercise training for elderly was effective in increasing physical activity in daily life.

Activities of Daily Living↗

PubMed1989

Ventricular ectopy in cardiac rehabilitation patients on exercise training and nonexercising days.

We evaluated the effect of routine exercise training sessions on the frequency of ventricular ectopic activity (VEA) in 18 coronary artery disease patients (mean age = 60 years) who were active participants in a cardiac rehabilitation program. Nine patients were classified as high risk and nine patients were low risk according to clinical status and cardiac catheterization criteria. Five patients in each group were on beta blockade, but none were on antiarrhythmic agents. Serial 24-h ECG monitoring was obtained on a routine supervised exercise day and nonexercise control day. VEA were compared during three time periods: (1) exercise training and recovery (4 h) and the corresponding 4 h during control, (2) activities of daily living (12 h), and (3) sleep (8 h). Both groups showed a moderate increase in total VEA during the three activity periods from control day to exercise day. However, this increase was only significant (p less than 0.05) in the high-risk group during the 12-h activity of daily living period postexercise. VEA was significantly greater (p less than 0.05) in the high-risk group during all activity intervals except the sleep period on the exercise day. We conclude that VEA occurs with similar frequency during exercise training or corresponding control periods. High-risk patients have significantly greater VEA on exercise and control days and show additional increased in VEA during activities of daily living (eating and driving) on exercise days.

Activities of Daily Living↗

PubMed1998

Influence of aerobic exercise training on brain natriuretic peptide secretion in patients in the chronic phase of myocardial infarction.

Brain natriuretic peptide (BNP) secretion increases after myocardial infarction (MI); its plasma level may reflect the degree of left ventricular dysfunction. This study examines how aerobic exercise therapy for MI influences BNP secretion. Subjects included 70 patients (mean age, 62.0+/-11.3 years) who were divided into four groups: (1) 20 patients with an anterior MI and exercise training; (2) 20 patients with an anterior MI and no exercise training; (3) 15 patients with an inferior MI and exercise training; and (4) 15 patients with an inferior MI and no exercise training. The training groups performed aerobic exercise 3 times a week for 2 months. Exercise intensity was defined as a heart rate of anaerobic threshold (AT), derived from the treadmill cardiopulmonary exercise testing at 1 month after the onset of MI. The subjects underwent cardiopulmonary exercise testing again at 3 months after the onset of MI. To measure BNP, blood samples were obtained in the resting state and immediately after the peak exercise. AT and peak oxygen uptake increased in the training group with anterior MI and in both the training and nontraining groups with inferior MI. Significant serial change in plasma BNP level was not observed in the inferior MI groups. Plasma BNP level decreased longitudinally only in the nontraining anterior MI group. It was concluded that exercise training in patients with an anterior MI could delay the recovery of left ventricular function, but will increase exercise tolerance.

Aged↗

PubMed2000

Effects of exercise training on cardiac function, gene expression, and apoptosis in rats.

This study determined the effects of exercise training on cardiac function, gene expression, and apoptosis. Rats exposed to a regimen of treadmill exercise for 13 wk had a significant increase in cardiac index and stroke volume index and a concomitant decrease in systemic vascular resistance compared with both age-matched and body weight-matched sedentary controls in the conscious state at rest. In exercise-trained animals, there was no change in the expression of several marker genes known to be associated with pathological cardiac adaptation, including atrial natriuretic factor, beta-myosin heavy chain, alpha-skeletal and smooth muscle actins, and collagens I and III. Exercise training, however, produced a significant induction of alpha-myosin heavy chain, which was not observed in rats with myocardial infarction. No histological features of cardiac apoptosis were observed in the treadmill-trained rats. In contrast, apoptotic myocytes were detected in animals with myocardial infarction. In summary, exercise training improves cardiac function without evidence of cardiac apoptosis and produces a pattern of cardiac gene expression distinct from pathological cardiac adaptation.

Actins↗

PubMed1985

Influence of caffeine on the resting metabolic rate of exercise-trained and inactive subjects.

The effect of caffeine on the resting metabolic rate (RMR) was investigated in endurance exercise-trained (N = 14) and inactive (N = 10) male individuals. Subjects were also classified into regular and non-regular consumers of caffeine. After an overnight fast, RMR was measured using an indirect calorimetry open circuit system. Thereafter, subjects orally consumed 300 mg of caffeine, after which RMR was measured for 90 min. Five of the exercise-trained subjects were also studied after the administration of a placebo. Plasma concentrations of glycerol and free fatty acid and respiratory exchange ratio (R) were measured at each 15-min interval. Before caffeine ingestion, no significant differences were observed in RMR, R, glycerol, free fatty acid and blood pressure levels between exercise-trained and inactive groups. Following caffeine consumption, a three-way analysis of variance revealed that inactive subjects exhibited a greater increase (P less than 0.05) in RMR than did exercise-trained subjects. No significant differences were observed in RMR response between regular or nonregular consumers of caffeine. Moreover, no differences were observed in glycerol, free fatty acid, heart rate, and blood pressure response between exercise-trained and inactive subjects and between regular and non-regular consumers of caffeine. These results suggest that endurance training results in a reduced thermogenic response to a caffeine challenge.

Adult↗

PubMed2006

Endothelial function and exercise training: evidence from studies using animal models.

This review summarizes and examines the evidence from experiments using animal models to determine the effect of endurance exercise training on endothelium-dependent dilation in the arterial circulation. The response of the endothelium to exercise training is complex and depends on a number of factors that include the duration of the training program, the size of the artery/arteriole, the anatomical location of the artery/arteriole, and the health of the individual. In healthy animals, short-term exercise training appears to cause enhanced endothelium-dependent dilation in some vascular beds, but it returns to normal levels as the duration of the training program increases. In general, evidence supports the notion that exercise training causes greater increases in endothelium-dependent dilation in various disease states than in healthy individuals. The evidence of a generalized effect of training on arterial endothelium in all regions of the body is inconsistent and appears to depend on the animal model used. Available results indicate that training duration, artery size, and anatomical location interact in ways not fully understood at this time to determine whether and to what extent endothelium-dependent dilation will be enhanced by exercise training.

Animals↗