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Results for “Exercise training”

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PubMed1990

Arm exercise training in the rehabilitation of patients with impaired ventricular function and heart failure.

Although exercise training is an accepted part of comprehensive coronary care programs in patients with coronary artery disease, it still remains to be demonstrated whether or not exercise training should also be applied to patients with impaired ventricular function. Circumstantial evidence exists that patients with impaired ventricular function may eventually benefit from an individually adapted exercise training program provided that contraindications for acceptance of cardiac patients to such a program are well observed. Our study is based on 22 patients with impaired ventricular function, of which 18 were at least 6 months after a Q-wave myocardial infarction and the remaining 4 after coronary artery bypass grafting. Eleven patients with impaired left ventricular function performing upper extremity (arm) ergometry were followed up for 36 months. These patients were trained twice weekly with exercise periods of 30 min duration. The reason for choosing arm ergometry training was that the peak heart rate obtained in arm ergometry is higher when compared to leg ergometry. Rate-pressure product and heart rate were higher for given submaximal work tasks in arm ergometry, while maximal work aerobic capacity was found to be lower in comparison to leg work. The assessment of our patients was based on cardiopulmonary testing, continuous electrocardiographic monitoring (48 h), two-dimensional echocardiography and equilibrium multigated radionuclide ventriculography (99mTc). Group 1, consisting of 11 patients with left ventricular ejection fraction (LVEF) 30.1 +/- 9.5%, were trained by arm exercise for 3 years with a significant increase in work capacity and LVEF. Group 2 consisted of 11 patients with LVEF 25.5 +/- 6.8% who underwent a 12 months' calisthenic program. Peak work capacity and LVEF remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Output↗

PubMed2006

Hemostatic response to postprandial lipemia before and after exercise training.

Chronic hypertriglyceridemia is thought to be atherogenic and is associated with an elevated thrombotic potential, both of which may be improved with aerobic exercise training. Eight subjects were tested for aerobic capacity, body composition, and postprandial lipemia (PPL), followed by 6 mo of exercise training and final testing. Blood samples were obtained for measurement of free fatty acid (FFA), triglycerides (TG), insulin (Ins), and glucose (Glu). Hemostatic variables including factor VII activity (FVIIa), tissue factor pathway inhibitor-factor Xa complex (TFPI/Xa), and plasminogen activator inhibitor-1 (PAI-1) antigen/activity as well as leukocyte tumor necrosis factor-alpha (TNF-alpha) gene expression were determined among four subjects. We found that the exercise training was of sufficient intensity to increase aerobic capacity (P < 0.0001) and improve body composition (P = 0.04). There were no differences between tests among PPL responses of FFA, TG, Ins, or Glu; however, the mean TG response and fat oxidation rate improved. PAI-1 antigen/activity, FVIIa, TFPI/Xa, and TNF-alpha gene expression were all improved after exercise training after adjusting for confounders. We conclude that aerobic exercise training reduces the potential for coagulation, improves fibrinolytic potential, and reduces leukocyte TNF-alpha gene expression after the ingestion of a high-fat meal.

Aged↗

PubMed2005

Improved insulin action following short-term exercise training: role of energy and carbohydrate balance.

Short-term exercise training improves insulin action, but the impact of replacing the energy expended during exercise to prevent energy deficit is unclear. The purpose of this study was to establish the role of an energy deficit in mediating improved insulin action after short-term exercise training. Two groups of previously sedentary, overweight/obese subjects performed 6 consecutive days of moderate-intensity walking to expend approximately 500 kcal/day. In one group, energy and carbohydrate expended during exercise was replaced [balance group (BAL), n = 8] and in the other group, energy was not replaced [deficit group (DEF), n = 8]. Insulin action (blood glucose uptake during glucose infusion) and selected lipids and adipokines were measured pre- and posttraining. Training increased estimated daily energy expenditure by approximately 500 kcal/day (DEF = 469 +/- 45, BAL = 521 +/- 48), generating an energy deficit in DEF (-481 +/- 24 kcal/day) but not BAL (+8 +/- 20 kcal/day). Insulin action increased 40% in DEF (P = 0.032) but not BAL (-8.4%, P = 0.107). Hepatic glucose production was suppressed during glucose infusion in DEF (30.2 +/- 9.5%, P = 0.037) but not BAL (-10.0 +/- 7.4%, P = 0.417). Fasting leptin concentrations declined in DEF but not BAL. Six days of exercise training without energy replacement significantly increased insulin action. Restoring energy balance by refeeding the energy and carbohydrate expended during exercise resulted in no change in insulin action. These findings suggest that changes in short-term energy and/or carbohydrate balance play a key role in mediating the beneficial effects of exercise on whole body and hepatic insulin action.

Blood Glucose↗

PubMed1986

Improvement of left ventricular contractile function by exercise training in patients with coronary artery disease.

To determine whether prolonged, intense exercise training can improve left ventricular function in patients with coronary artery disease, we studied 25 patients, 52 +/- 2 years old (mean +/- SE), who completed a 12 month program of endurance exercise training and 14 additional patients with comparable maximal exercise capacities and ejection fractions who did not exercise. The training program consisted of endurance exercise of progressively increasing intensity, frequency, and duration. During the last 3 months the patients were running an average of 18 miles/week, or doing an equivalent amount of exercise on a cycle ergometer. Maximal attainable VO2 increased 37% (p less than .001). Of the 10 patients with effort angina, five became asymptomatic, three experienced less angina, and two were unchanged after training. Ejection fraction was determined by equilibrium radionuclide ventriculography. At rest, ejection fraction was 53 +/- 3% before and 54 +/- 3% after training (p = NS). Ejection fraction did not change during maximal supine exercise before training (52 +/- 3%), but after training it increased to 58 +/- 3% (p less than .01). During maximal exercise, systolic blood pressure and the rate-pressure product were higher after training. The systolic blood pressure-end-systolic volume relationship was shifted upward and to the left, with an increase in maximal systolic blood pressure (p less than .001) and a smaller end-systolic volume (p less than .05), providing evidence for an improvement in contractile state after training. In patients who did not participate in training neither this relationship nor the ejection fraction response to exercise was changed after 12 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2003

Baroreflex buffering in sedentary and endurance exercise-trained healthy men.

Baroreflex buffering plays an important role in arterial blood pressure control. Previous reports suggest that baroreflex sensitivity may be altered in endurance exercise-trained compared with untrained subjects. It is unknown, however, if in vivo baroreflex buffering is altered in the endurance exercise-trained state in humans. Baroreflex buffering was determined in 36 healthy normotensive men (18 endurance exercise-trained, 41+/-5 [SEM] years; 18 untrained, 41+/-4 years) by measuring the potentiation of the systolic blood pressure responses to a phenylephrine bolus and to incremental phenylephrine infusion during compared with before ganglionic blockade with trimethaphan. The exercise-trained men had a lower resting heart rate and higher maximal oxygen consumption and heart rate variability than the sedentary control subjects (all P=0.01). Mean levels and variability of blood pressure, cardiovagal baroreflex sensitivity (change in heart rate/change in systolic blood pressure), and basal muscle sympathetic nerve activity were not different in the two groups. The systolic blood pressure responses to phenylephrine were not different in the endurance-trained and untrained men before or during ganglionic blockade (P>0.6). Measures of baroreflex buffering with the use of a phenylephrine bolus (3.9+/-0.8 versus 4.0+/-0.7, trained versus untrained, P=0.85) and incremental infusion (2.8+/-0.4 versus 2.5+/-0.6, P=0.67) were similar in the two groups. Baroreflex buffering does not differ in endurance exercise-trained compared with untrained healthy men. These results support the concept that habitual vigorous endurance exercise does not modulate in vivo baroreflex buffering in healthy humans.

Adrenergic alpha-Agonists↗

PubMed2002

Effect of exercise training on skeletal muscle fibre characteristics in men with chronic heart failure. Correlation between skeletal muscle alterations, cytokines and exercise capacity.

BACKGROUND: In patients with congestive heart failure (CHF) there is a shift from aerobic type I muscle fibres to less aerobic type II fibres. Exercise training has been shown to have beneficial effects on exercise performance, peripheral pathology and the neurohumoral profile in stable patients with CHF. This study evaluated the effect of a 3 month exercise training program on skeletal muscle characteristics and the correlation of these to cytokines and exercise capacity in CHF patients. METHODS: Skeletal muscle biopsies for enzyme-histochemical analysis were performed in 15 CHF patients in New York Heart Association classes II-III, with a mean ejection fraction of 33+/-5% before and after a 12 week training period. The patients were trained for 30 min, five times a week at 80% of the peak heart rate achieved at baseline ergometer cycle test. Fifteen healthy men were used as controls. Plasma samples were examined by enzyme immunoassays for levels of pro-inflammatory cytokines. RESULTS: (a) At baseline we found muscle atrophy in five of the patients. The percent area of type I fibres (40.7+/-12.0 vs. 56.4+/-11.0%, P<0.05) and the thickness of type IIA (56.10+/-7.8 vs. 71.6+/-11.9 microm, P<0.001) and B-fibres (49.0+/-8.9 vs. 63.9+/-10.6 microm, P<0.001) were reduced, whereas the percent area of type IIA fibres (52.1+/-13.3 vs. 36.4+/-9.9%, P<0.05) was increased in heart failure patients compared to healthy controls. There was a modest correlation between fibre thickness and the level of interleukin 6 (r=-0.657, P=0.008). (b) After exercise training there was a reduction in muscle area examined by light-microscopy, measured as a percentage of field (-2.7, P=0.003) with an concomitant increase in interstitium. This reduction correlated to the increase in the 6-min walk test (r=-0.558, P=0.031). The thickness of type IIB fibres increased (+5.6 microm, P=0.068) and the area of type I fibres decreased (-6.1%, P=0.062). CONCLUSIONS: Patients with CHF have a relatively increased area of type IIA fibres and a relatively decreased area of type I fibres compared to healthy individuals. The thickness of type IIA and type IIB fibres is decreased compared to normal individuals. A modest negative correlation between the level of interleukin 6 and fibre thickness at baseline, suggests that inflammatory cytokines may be involved in the pathogenesis of the CHF related myopathy. A significant correlation between the reduction of muscle area, with increased interstitum, and the increase in the 6-min walk test may indicate that the improvement is due to increased capillary density permitting better flow reserve to exercising muscles.

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PubMed2000

Exercise training enhances glycolytic and oxidative enzymes in canine ventricular myocardium.

Aerobic exercise training evokes adaptations in the myocardial contractile machinery that enhance cardiac functional capacity; in comparison, the effects of training on the myocardium's energy generating pathways are less well characterized. This study tested the hypothesis that aerobic exercise training can increase the capacities of the major pathways of intermediary metabolism in canine myocardium. Mongrel dogs were conditioned by a 9-week treadmill running program or cage rested for 4 weeks. Exercise conditioning was evidenced by 26% and 22% decreases (P<0.05) in respective heart rates at rest and during submaximal exercise and by a 40% increase (P<0.05) in citrate synthase (CS) activity of the vastus lateralis. Glycolytic, TCA cycle, and beta-oxidative enzymes were assayed in myocardial extracts at 37 degrees C. Relative to sedentary controls, training increased glyceraldehyde 3-phosphate dehydrogenase (GAPDH) activity by 49% in left and 33% in right ventricle, and pyruvate kinase, CS, and 3-hydroxyacyl CoA dehydrogenase (HADH) activities by 74%, 91%, and 77%, respectively, in left ventricle (P<0.05). Immunoblotting further confirmed that training increased left ventricular contents of CS and GAPDH. Other measured enzymes (hexokinase, phosphofructokinase, lactate dehydrogenase, alpha-ketoglutarate dehydrogenase, malate dehydrogenase) were not altered by training in either ventricle. Kinetic analyses revealed increased maximum rates but unaltered substrate affinities of GAPDH, CS and HADH following training. Thus, aerobic exercise training augments the intermediary metabolic capacity of canine myocardium by selectively increasing the concentrations of regulatory enzymes of glycolysis and oxidative metabolism.

Animals↗

PubMed1979

Conditioning effects of chronic infusions of dobutamine. Comparison with exercise training.

We studied the conditioning effects of chronic infusion of dobutamine and exercise training in three groups of chronically instrumented dogs. One group was infused with normal saline, a second group was infused with dobutamine (40 mug/kg per min), and the third group was exercised on a treadmill at 4 mph, up a 10 degrees incline. Each group was either infused or exercised for 2 h a day, 5 d a week for 5 consecutive wk. Resting heart rate and arterial blood lactate concentration, measured at weekly intervals, decreased progressively in the dobutamine and exercise groups, but not in the group that received normal saline infusion. Cardiovascular responses to submaximal treadmill exercise were not changed by 5 wk of normal saline infusion. However, the increases in heart rate, cardiac output, mean aortic blood pressure, arterial blood lactate, plasma renin activity, and norepinephrine concentration during exercise were significantly smaller after 5 wk of conditioning with either dobutamine or exercise training. After conditioning, the increases in arteriovenous oxygen difference during exercise were larger in the latter two groups, but the increases in total body oxygen consumption did not differ before and after conditioning. To assess ventricular function, we intravenously infused methoxamine both before and after conditioning. The slope of the line that related systolic aortic blood pressure and mean left atrial pressure increased in the animals conditioned with either dobutamine or exercise, indicating enhanced myocardial contractility. Left ventricular blood flow was lower in these two groups of animals than it was in the normal saline group. Left ventricular weight did not differ among the three groups. Our results show that chronic infusion of dobutamine produced cardiovascular and metabolic conditioning effects like those produced by exercise training, and further suggest that sympathetic stimulation during exercise plays a role in physical conditioning.

Animals↗

PubMed1998

Influence of exercise training on blood viscosity in patients with coronary artery disease and impaired left ventricular function.

Exercise training has recently become an accepted therapeutic modality in chronic heart failure after myocardial infarction. Because the therapeutic mechanism behind it is controversial and not well understood, we analyzed the influence of exercise training on blood viscosity. Twenty-five patients with chronic heart failure (ejection fraction < 40%) after myocardial infarction were randomly assigned to either an 8-week intensive exercise program at a residential rehabilitation center or 8 weeks of sedentary life at home. Exercise consisted of two 1-hour walking sessions per day and four intensive bicycle ergometer training sessions of 40 minutes at 70% to 80% peak exercise capacity per week. Whole blood viscosity, viscosity at standardized hematocrit of 45% (P45) at high and low shear rates, and plasma viscosity were measured in a Couette-type viscometer before, during, and at the end of the study period. Exercise training, which significantly increased maximal cardiac output and oxygen uptake, did not change plasma viscosity, whole blood viscosity, and P45 significantly. Sedentary controls, however, had a higher whole blood viscosity and P45 after 8 weeks. No statistical difference was found, however, between the two groups. We conclude that blood rheology remains unaffected by exercise training in patients with chronic heart failure. The improvement of blood viscosity remains an interesting therapeutic option for the symptoms of these patients, which must be achieved by methods other than exercise training.

Blood Viscosity↗

PubMed2002

Combined effect of ACE inhibitor and exercise training on insulin resistance in type 2 diabetic rats.

The aim of this study was to investigate whether a combined treatment of ACE inhibitor and exercise training is more effective than either treatment alone in alleviating the insulin resistant states in the Otsuka Long-Evans Tokushima Fatty (OLETF) rat, a model of type 2 diabetes. OLETF rats (25 weeks old) were randomly divided into 5 groups; sedentary control, exercise-trained, temocapril (ACE inhibitor; 2 mg/kg/day)-treated, with and without exercise, and losartan (AT1 receptor antagonist; 1 mg/kg/day)-treated. Long-Evans Tokushima Otsuka rats were used as a non-diabetic control. Body weight, the amount of abdominal fat and blood pressure were higher for OLETF rats than for control rats. However, glucose infusion rate (GIR), an index of insulin resistance, was decreased greatly in OLETF rats. The fasting levels of blood glucose, insulin and lipids were also increased in the diabetic strain. In OLETF rats, both temocapril and losartan reversed hypertensive states significantly, whereas GIR and hyperlipidemia were improved when rats were treated with ACE inhibitors, but not with the AT1 receptor antagonist. Exercise training decreased body weight and the amount of abdominal fat, and also increased GIR in parallel with improved dislipidemia. The combination of the ACE inhibitor with exercise training also improved obesity, hyperinsulinemia, dislipidemia and fasting level of blood glucose, and this combination resulted in the greatest improvement of insulin resistance. These results suggest that the combination of ACE inhibitor and exercise training may be a beneficial treatment for mixed diabetic and hypertensive conditions.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1993

Rigorous exercise training increases superoxide dismutase activity in ventricular myocardium.

Controversy exists as to the effect of endurance training on myocardial antioxidant enzyme activity. These experiments sought to clarify this issue by examining antioxidant enzyme activities in the rat ventricular myocardium in response to different intensities and durations of exercise training. Female Fischer-344 rats (120 days old) were assigned to either a sedentary control group or one of nine exercise training groups. Animals were exercised on a motorized treadmill for 10 wk; combinations of three durations (30, 60, and 90 min/day), and three levels of exercise intensity (low, moderate, and high) were studied. Exercise training did not alter (P > 0.05) citrate synthase, catalase, or glutathione peroxidase activities in the right or left ventricle. In contrast, high-intensity exercise (all durations) and moderate-intensity exercise (90 min/day) resulted in a significant increase (P < 0.05; +28-30%) in right ventricular superoxide dismutase (SOD) activity. Similarly, high-intensity exercise training (all durations) resulted in a significant elevation (P < 0.05; +14-26%) of left ventricular SOD activity. Furthermore, low- and moderate-intensity exercise training of long duration (i.e., 60-90 min/day) resulted in significant increases (P < 0.05; +10-23%) in left ventricular SOD activity. These data support the hypothesis that high-intensity exercise (> or = 30 min/day) or moderate-intensity exercise of long duration (> or = 60 min/day) is effective in upregulating SOD activity in the ventricular myocardium.

Animals↗

PubMed2006

Exercise training reverses downregulation of HSP70 and antioxidant enzymes in porcine skeletal muscle after chronic coronary artery occlusion.

Oxidative stress is associated with muscle fatigue and weakness in skeletal muscle of ischemic heart disease patients. Recently, it was found that endurance training elevates protective heat shock proteins (HSPs) and antioxidant enzymes in skeletal muscle in healthy subjects and antioxidant enzymes in heart failure patients. However, it is unknown whether coronary ischemia and mild infarct without heart failure contributes to impairment of stress proteins and whether exercise training reverses those effects. We tested the hypothesis that exercise training would reverse alterations in muscle TNF-alpha, oxidative stress, HSP70, SOD (Mn-SOD, Cu,Zn-SOD), glutathione peroxidase (GPX), and catalase (CAT) due to chronic coronary occlusion of the left circumflex (CCO). Yucatan swine were divided into three groups (n = 6 each): sedentary with CCO (SCO); 12 wk of treadmill exercise training following CCO (ECO); and sham surgery controls (sham). Forelimb muscle mass-to-body mass ratio decreased by 27% with SCO but recovered with ECO. Exercise training reduced muscle TNF-alpha and oxidative stress (4-hydroxynonenal adducts) caused by CCO. HSP70 levels decreased with CCO (-45%), but were higher with exercise training (+348%). Mn-SOD activity, Mn-SOD protein expression, and Cu,Zn-SOD activity levels were higher in ECO than SCO by 72, 82, and 112%, respectively. GPX activity was 177% greater in ECO than in SCO. CAT trended higher (P = 0.059) in ECO compared with SCO. These data indicate that exercise training following onset of coronary artery occlusion results in recovery of critical stress proteins and reduces oxidative stress.

Adaptation, Physiological↗

PubMed2004

Endurance exercise training increases insulin responsiveness in isolated adipocytes through IRS/PI3-kinase/Akt pathway.

Endurance exercise training promotes important metabolic adaptations, and the adipose tissue is particularly affected. The aim of this study was to investigate how endurance exercise training modulates some aspects of insulin action in isolated adipocytes and in intact adipose tissue. Male Wistar rats were submitted to daily treadmill running (1 h/day) for 7 wk. Sedentary age-matched rats were used as controls. Final body weight, body weight gain, and epididymal fat pad weight did not show any statistical differences between groups. Adipocytes from trained rats were smaller than those from sedentary rats (205 +/- 16.8 vs. 286 +/- 26.4 pl; P < 0.05). Trained rats showed decreased plasma glucose (4.9 +/- 0.13 vs. 5.3 +/- 0.07 mM; P < 0.05) and insulin levels (0.24 +/- 0.012 vs. 0.41 +/- 0.049 mM; P < 0.05) and increased insulin-stimulated glucose uptake (23.1 +/- 3.1 vs. 12.1 +/- 2.9 pmol/cm(2); P < 0.05) compared with sedentary rats. The number of insulin receptors and the insulin-induced tyrosine phosphorylation of insulin receptor-beta subunit did not change between groups. Insulin-induced tyrosine phosphorylation insulin receptor substrates (IRS)-1 and -2 increased significantly (1.57- and 2.38-fold, respectively) in trained rats. Insulin-induced IRS-1/phosphatidylinositol 3 (PI3)-kinase (but not IRS-2/PI3-kinase) association and serine Akt phosphorylation also increased (2.06- and 3.15-fold, respectively) after training. The protein content of insulin receptor-beta subunit, IRS-1 and -2, did not differ between groups. Taken together, these data support the hypothesis that the increased adipocyte responsiveness to insulin observed after endurance exercise training is modulated by IRS/PI3-kinase/Akt pathway.

Adipocytes↗

PubMed1998

Exercise training has little effect on HDL levels and metabolism in men with initially low HDL cholesterol.

Low concentrations of high-density lipoprotein cholesterol (HDL-C) are a recognized risk factor for atherosclerotic cardiovascular disease. Exercise is often recommended to increase HDL-C, but the effect of exercise training on HDL levels and metabolism in subjects with low HDL concentrations is not well defined. The present study compared the HDL response to 12 months of supervised endurance exercise training without weight loss in 17 men aged 26 49 years with initially low ( < 40 mg/dl, N=7) or normal ( > 44 mg/dl, N=10) HDL-C levels. HDL-C levels and HDL apolipoprotein metabolism were assessed while the subjects consumed controlled diets before and after the year of training. Increases in total (5.1+/-2.8 versus 1.9+/-4.2 mg/dl, P=0.08) and HDL2 (3.8+/-2.9 versus 0.4+/-1.1 mg/dl, P=0.01) cholesterol were greater in men with normal initial HDL-C levels. Catabolic rates for HDL apolipoproteins decreased 7-14% and biological half-lives increased 10-15% after exercise training in subjects with normal HDL, but were unchanged in the low HDL-C group. HDL apolipoprotein synthetic rates were not consistently affected by exercise training in either group. Postheparin lipoprotein lipase activity increased 27%, the clearance rate of intravenous triglycerides increased 14%, and apolipoprotein B levels decreased 16% with training in subjects with normal HDL-C but were unchanged in the low HDL-C group. We conclude that the ability to increase HDL-C levels through endurance exercise training is limited in subjects with low initial HDL-C, possibly because exercise training in such subjects fails to alter triglyceride metabolism.

Adult↗

PubMed1990

Different metabolic responses to exercise training programmes in single rat muscle fibres.

The aim of this report is to elucidate the effects of exercise training on metabolic properties of different muscle fibre types of the rat hindlimb. Single muscle fibres were dissected from soleus (SOL) or extensor digitorum longus (EDL) muscles of Wistar strain male rats trained on a treadmill for 16 weeks. Each fibre was typed histochemically (SO, slow-twitch oxidative; FOG, fast-twitch oxidative glycolytic; FG, fast-twitch glycolytic). Then glycolytic and oxidative enzymes (CK, LDH, PFK, PK, SDH, and MDH) activities were measured biochemically. Slow-type fibres (SO) were hypertrophied following endurance training and fast-twitch fibres (FOG and FG) were hypertrophied following sprint training. In EDL muscles the distribution of the slow-type fibres was reduced following the sprint training. The activity of glycolytic enzymes increased significantly in the fast-type fibres (FOG and FG) following sprint training, while oxidative enzymes activities increased in both fast (FOG and FG) and slow (SO) muscle fibres following the endurance training. Neither glycolytic nor oxidative enzymes' activities always increased equally in all types of fibre following exercise training. Consequently, the metabolic profiles in each type of single muscle fibre were affected differently by different intensities of exercise training. These results suggest that the functional (enzymes activity) and structural (muscle fibre hypertrophy) changes of skeletal muscle fibre following exercise training appeared gradually, and would be controlled by different factors.

Animals↗

PubMed2000

Exercise training improves left ventricular isovolumic relaxation.

PURPOSE: Left ventricular (LV) diastolic function is an important determinant of aerobic fitness. The purpose of this paper was to investigate the relationship between aerobic fitness and the rate and extent of isovolumic LV relaxation. METHODS: Two series of experiments were performed utilizing both human and animal models. In the first series of experiments, the relationship between LV diastolic time intervals and exercise capacity was assessed in two groups of collegiate men (N = 18) with variable peak run times (Bruce protocol). In the second series of experiments, the extent of LV relaxation was examined in sedentary and exercise-trained rats (treadmill running), using an isolated, isovolumic heart preparation. Subsequent morphological assessment was also performed in rats. RESULTS: At rest, men with greater peak treadmill time had a shorter resting LV isovolumic relaxation time (R-R interval adjusted 1000 ms) (long duration runners, 84+/-5 ms vs short duration runners, 105+/-7 ms, P < 0.05) despite a similar LV diastolic interval. Peak treadmill time was inversely correlated to LV isovolumic relaxation time (R-R interval adjusted 1000 ms) (r = -0.55; P < 0.02). In animal studies (N = 26), the LV pressure-volume relationship was shifted rightward in exercise-trained rats (P = 0.003). Exercise-trained rats had an increased LV inner diameter (sedentary, 5.1+/-0.35 mm vs exercise-trained, 6.1+/-0.28 mm, P < 0.05) and a thicker interventricular septum (sedentary, 1.52+/-0.06 mm vs exercise-trained, 1.72+/-0.09 mm, P < 0.05). CONCLUSION: This study suggests that both the rate and extent of LV isovolumic relaxation is enhanced with exercise training. Further study is required to understand the interrelationship between exercise and diastolic function.

Animals↗

PubMed1993

Exercise training increases GLUT-4 protein in rat adipose cells.

The relative abundance and subcellular distribution of the GLUT-1 and GLUT-4 glucose transporter isoforms were determined in basal and insulin-stimulated adipose cells from wheel cage exercise-trained rats and compared with both age-matched sedentary controls and young cell size-matched sedentary controls. Exercise training increased total estimated GLUT-4 by 67 and 54% compared with age-matched and young controls, respectively. Total estimated GLUT-1 per cell was not significantly different among the three groups. Expressed per cell, plasma membrane GLUT-4 protein in basal adipose cells from exercise-trained and age-matched control rats was 2.5-fold greater than in young controls (P < 0.05) and was associated with higher basal rates of glucose transport in these cells (P < 0.02). In insulin-stimulated cells, plasma membrane GLUT-4 was 67% greater in the exercise-trained animals than young controls (P < 0.01), and 31% greater than in age-matched controls. Rates of glucose transport were correspondingly higher. In basal cells, low-density microsomal GLUT-4 from exercise-trained rats was approximately twofold greater than from age-matched controls and young controls. With insulin stimulation, GLUT-4 in low-density microsomes decreased to similar levels in all groups. We conclude that the total amount of GLUT-4 protein, but not GLUT-1, is increased in adipose cells by exercise training and that this increase in GLUT-4 is due primarily to an increase in intracellular GLUT-4.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

PubMed2004

Would the addition of TENS to exercise training produce better physical performance outcomes in people with knee osteoarthritis than either intervention alone?

OBJECTIVE: To examine if the addition of transcutaneous electrical nerve stimulation (TENS) to exercise training would produce better physical outcomes than TENS or exercise alone in people with knee osteoarthritis. DESIGN: Sixty-two subjects were randomly allocated to four groups. INTERVENTIONS: Patients received either (1) TENS, (2) placebo stimulation, (3) exercise training, or (4) TENS and exercise training five days a week for four weeks. MAIN OUTCOME MEASURES: The isometric peak torque, spatiotemporal gait parameters and range of knee movement were assessed in treatment session1, session10 and session20 and the four-week follow-up. RESULTS: By session20, the TENS and exercise group demonstrated an average of 26.6% cumulative gain in the knee extensor peak torque for the different knee positions (all p < 0.05). Although the between-group difference was short of being statistically significant, the gain found in the TENS and exercise group was greater than that found in the other three groups. The TENS and exercise group also tended to show greater cumulative increase in stride length (12.6%, p = 0.006), walking cadence (9.3%, p = 0.098) and gait velocity (22.4%, p = 0.034) than the other groups. By session20, it was the only group that produced a significant increase in the range of knee motion during walking (12.0%, p = 0.000). The TENS group and the exercise group both demonstrated some improvements in the above physical outcomes, but negligible change was found in the group receiving placebo stimulation (all p > 0.05). CONCLUSION: No significant difference was found among the four treatment protocols, but the addition of TENS to exercise training tended to produce the best overall improvement in physical outcomes in people with knee osteoarthritis.

Aged↗