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Exercise training alters endothelium-dependent vasoreactivity of rat abdominal aorta.

We tested the hypothesis that adaptations in peripheral arterial vasoreactivity are induced by exercise training. Male rats were trained to run on a treadmill at 30 m/min (15 degrees incline) for 1 h/day 5 days/wk for 10-12 wk. Efficacy was indicated by a 51% increase (P < 0.05) in citrate synthase activity in soleus muscle of exercise-trained (ET) rats compared with that of sedentary (SED) control rats. Responses to vasoactive compounds were examined in vitro using rings of abdominal aorta. Maximal isometric contractile tension evoked by KCl, norepinephrine (NE), and phenylephrine were not different between groups; sensitivity to phenylephrine was also not different between groups. However, sensitivity was lower for both KCl and NE in vessels from ET animals. Endothelium removal did not influence KCl sensitivity but did abolish the difference in NE sensitivity of vessel segments between ET and SED animals. Maximal vasodilator responses induced by acetylcholine (ACh; NE or prostaglandin F2 alpha preconstriction) were greater in vessel rings from ET rats. However, dilatory responses by sodium nitroprusside (NE or prostaglandin F2 alpha preconstriction) and forskolin (NE preconstriction) were not different between groups, indicating that the augmented ACh-induced dilatory response resulted from an adaptation of the endothelium. Blockade of nitric oxide synthase activity diminished ACh-induced vasodilation by 79 and 100% in SED and ET rats, respectively. These results indicate that training alters vasomotor function in rat abdominal aortas through adaptations of both endothelium and smooth muscle.

Animals↗

Exercise training prevents decline in stroke volume during exercise in young healthy subjects.

Stroke volume (SV) increases above the resting level during exercise and then declines at higher intensities of exercise in sedentary subjects. The purpose of this study was to determine whether an attenuation of the decline in SV at higher exercise intensities contributes to the increase in maximal cardiac output (Qmax) that occurs in response to endurance training. We studied six men and six women, 25 +/- 1 (SE) yr old, before and after 12 wk of endurance training (3 days/wk running for 40 min, 3 days/wk interval training). Cardiac output was measured at rest and during exercise at 50 and 100% of maximal O2 uptake (Vo2max) by the C2H2-rebreathing method. VO2max was increased by 19% (from 2.7 +/- 0.2 to 3.2 +/- 0.3 l/min, P less than 0.001) in response to the training program. Qmax was increased by 12% (from 18.1 +/- 1 to 20.2 +/- 1 l/min, P less than 0.01), SV at maximal exercise was increased by 16% (from 97 +/- 6 to 113 +/- 8 ml/beat, P less than 0.001) and maximal heart rate was decreased by 3% (from 185 +/- 2 to 180 +/- 2 beats/min, P less than 0.01) after training. The calculated arteriovenous O2 content difference at maximal exercise was increased by 7% (14.4 +/- 0.4 to 15.4 +/- 0.4 ml O2/100 ml blood) after training. Before training, SV at VO2max was 9% lower than during exercise at 50% VO2max (P less than 0.05). In contrast, after training, the decline in SV between 50 and 100% VO2max was only 2% (P = NS). Furthermore, SV was significantly higher (P less than 0.01) at 50% VO2max after training than it was before. Left ventricular hypertrophy was evident, as determined by two-dimensional echocardiography at the completion of training. The results indicate that in young healthy subjects the training-induced increase in Qmax is due in part to attenuation of the decrease in SV as exercise intensity is increased.

Adult↗

Selection criteria for exercise training in patients with COPD.

The physical performance of patients with chronic obstructive pulmonary disease (COPD) is limited mainly by pathophysiological derangements of the ventilatory system. Thus, the exercise performance can be ameliorated by increasing the level of ventilation that they can sustain, or by reducing the ventilatory requirement for a given level of activity. Almost all studies have yielded negative results in COPD patients, in terms of exercise training having the ability to improve VEmax. The only way to reduce the ventilatory requirement is to reduce CO2 output. Lower levels of lactate result in less non-metabolic CO2 produced by bicarbonate buffering. This is the likely mechanism responsible for a lower ventilatory requirement for work rates above the pre-training anaerobic threshold. We specifically wished to determine, whether a program of intensity, frequency and duration known capable of producing a physiologic training effect in healthy subjects, would do so in COPD patients. Further, we sought to determine, whether exercise training at a work rate associated with lactic acidosis is more effective in inducing a training effect in COPD patients than a work rate not associated with lactic acidosis. Nineteen COPD patients were selected and performed an incremental test as well as two square wave tests at a low and a high work rate. Identical tests were performed after an 8-week program of cycle ergometer training either for 45 min/day at a high work rate or for a proportionally longer time at a low work rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗

Skin blood flow and sweating changes following exercise training and heat acclimation.

Eight subjects underwent an exercise training program (10 days at 75% VO2max for 1 h/day at 25 degrees C db/13 degrees C wb) and a heat-acclimation program (10 days at 50% VO2max for 1 h/day at 35 degrees C db/32 degrees C wb). The relations of chest sweat rate and of forearm blood flow to internal temperature were determined for each subject at a 25 degrees C ambient temperature before training, between training and acclimation, and following acclimation. Training shifted the vasodilation and sweating thresholds toward lower internal temperatures, and acclimation further lowered these thresholds. All threshold shifts were statistically significant (P less than 0.05). Training and acclimation both appeared to increase the slope of the sweating relation, but these effects were not statistically significant. Changes in the slope of the blood flow relation were small and inconsistent. Since arm blood flow is higher at any given internal temperature after acclimation, the lower blood flow which is reported to accompany heat acclimation must result from the lower body temperatures.

Acclimatization↗

Nonuniform effects of endurance exercise training on vasodilation in rat skeletal muscle.

Endurance exercise training (Ex) has been shown to increase maximal skeletal muscle blood flow. The purpose of this study was to test the hypothesis that increased endothelium-dependent vasodilation is associated with the Ex-induced increase in muscle blood flow. Furthermore, we hypothesized that enhanced endothelium-dependent dilation is confined to vessels in high-oxidative muscles that are recruited during Ex. To test these hypotheses, sedentary (Sed) and rats that underwent Ex (30 m/min x 10% grade, 60 min/day, 5 days/wk, 8-12 wk) were studied using three experimental approaches. Training effectiveness was evidenced by increased citrate synthase activity in soleus and vastus lateralis (red section) muscles (P < 0.05). Vasodilatory responses to the endothelium-dependent agent acetylcholine (ACh) in situ tended to be augmented by training in the red section of gastrocnemius muscle (RG; Sed: control, 0.69 +/- 0.12; ACh, 1.25 +/- 0.15; Ex: control, 0.86 +/- 0.17; ACh, 1.76 +/- 0.27 ml x min(-1) x 100 g(-1) x mmHg(-1); 0.05 < P < 0.10 for Ex vs. Sed during ACh). Responses to ACh in situ did not differ between Sed and Ex for either the soleus muscle or white section of gastrocnemius muscle (WG). Dilatory responses of second-order arterioles from the RG in vitro to flow (4-8 microl/min) and sodium nitroprusside (SNP; 10(-7) through 10(-4) M), but not ACh, were augmented in Ex (vs. Sed; P < 0.05). Dilatory responses to ACh, flow, and SNP of arterioles from soleus and WG muscles did not differ between Sed and Ex. Content of the endothelial isoform of nitric oxide synthase (eNOS) was increased in second-order, fourth-order, and fifth-order arterioles from the RG of Ex; eNOS content was similar between Sed and Ex in vessels from the soleus and WG muscles. These findings indicate that Ex induces endothelial adaptations in fast-twitch, oxidative, glycolytic skeletal muscle. These adaptations may contribute to enhanced skeletal muscle blood flow in endurance-trained individuals.

Animals↗

An overview of the problem: exercise training and orthostatic intolerance.

The questions, whether endurance exercise training (a) induces orthostatic intolerance and (b) alters blood pressure regulation during orthostasis, have been debated since the early 1970s. This symposium presents data that both support and discount the concepts. In addition, data were presented that document invasive and noninvasive techniques of measurement used during investigations of baroreflex and hemodynamic mechanisms of blood pressure regulation during lower body negative pressure (LBNP), a laboratory technique that simulates orthostasis. These techniques and the results obtained enabled the formulation of a hypothetical mechanism of explanation of the "pro and con" of the debated questions.

Adaptation, Physiological↗

The effects of menopausal status and exercise training on serum lipids and the activities of intravascular enzymes related to lipid transport.

The study purpose was to compare the effect of exercise training on serum lipid and apolipoprotein concentrations and the activities of intravascular enzymes related to lipid transport in previously untrained eumenorrheic, premenopausal (PRM) women (n = 21; mean age, 36 +/- 3 years) and estrogen-free postmenopausal (POM) women (n = 16; mean age, 68 +/- 8 years). Subjects trained at a progressive intensity and duration (50% to 75% maximal O2 consumption [VO2max], 200 to 300 kcal/session) 4 d/wk for 12 weeks. Before and after training, VO2max, body weight, relative body fat, and fasting blood samples were obtained following 2 weeks on a standardized diet designed to maintain body weight and during the early follicular stage for the PRM group. Blood samples were analyzed for serum total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), the cholesterol content of the HDL3 subfraction, apolipoprotein (apo)A-I and apoB, lipoprotein(a), and the activity of lecithin:cholesterol acyltransferase (LCAT). Total and hepatic triglyceride lipase activity (HTGLA) were determined from plasma samples obtained after heparin administration. The cholesterol content of the low-density lipoprotein (LDL) and HDL2 subfractions and endothelial-bound lipoprotein lipase activity (LPLA) were calculated. A two (group) x two (time) multivariate ANOVA (MANOVA), with repeated measures for time indicated that the exercise-induced changes in physiological measurements, serum lipid or apolipoprotein concentrations, or enzyme activities did not differ between groups. Serum concentrations of TC, LDL-C, and HDL3 cholesterol, TG, and apo A-I and apoB were higher in POM women compared with the PRM group (P < .05 for all). For the combined groups, body weight and relative body fat did not change with training, but VO2max increased an average of 18.5% (P < .05). LPLA, HTGLA, and LCAT activity were unaltered with exercise training. Except for a small but significant decrease in HDL-C (-5.5%) and an elevation in apoB (4.3%; P < .05 for both), the concentrations of serum lipids and apolipoproteins did not change over the training period. We conclude that in previously untrained women, menopausal status does not influence the exercise training response of serum lipids or apolipoproteins or activities of intravascular enzymes related to lipid transport.

Adult↗

Effects of ingesting a high-fat diet upon exercise-training cessation on fat accretion in the liver and adipose tissue of rats.

The purpose of the present study was to determine if exercise trained rats might benefit from protection against fat accumulation in response to an obesity stimulus initiated upon training cessation. Two groups of female rats were either treadmill trained for 8 weeks (DTr) or remained sedentary (Sed). They were then submitted either to a high-fat diet (HF; 42 E%) or kept on a standard diet (SD; 12.5 E% lipids) for another 6 weeks while remaining sedentary. Fat accumulation in liver and adipocytes along with fat-cell diameter and plasma free fatty acid (FFA) levels were measured 0, 2, and 6 weeks after training cessation. Immediately after the training period (t = 0), DTr rats exhibited similar body mass and higher dietary intake but smaller body fat content (4 fat pads) compared with Sed rats. DTr rats, under both diets, exhibited higher gains in body fat than Sed rats (DTr vs. Sed, 71% vs. 8% and 132% vs. 55% for SD and HF, respectively), such that fat mass in all 4 depots was similar to Sed rats 6 weeks after training cessation. Despite higher adipocyte fat accretion, liver lipid infiltration was not increased in DTr animals and plasma FFA levels were lower throughout the detraining period. In addition, plasma leptin levels remained lower in DTr animals throughout the detraining period under the HF diet condition. The present results indicate that previously exercise trained rats are not protected against adipocyte fat accumulation whether they ingest a standard or a high-fat diet.

Adipocytes↗

The impact of long-term exercise training on psychological function in older adults.

The effect of long-term aerobic training on psychological function was examined in 87 sedentary older adults who engaged in a year-long endurance exercise training program compared with a nonexercising control group. In addition to improved cardiovascular fitness, a positive change in self-reported morale was found for the exercise condition. Of the cognitive functions measured, a significant effect was noted for the Wechsler Memory Scale (WMS) Logical Memory subtest; however, this effect was caused by a decline in performance from pre- to posttesting in the control group. Long-term exercise training had little, if any, effect on improving cognitive function in this older adult sample.

Affect↗

Treadmill exercise training increases the oxidative capacity of chicken iliotibialis muscle.

The number of fibers staining for the oxidative enzyme succinic dehydrogenase (SDH) was measured in the iliotibialis lateralis caudalis muscle of the domestic fowl before treadmill training and after 6 wk and 15 wk of training, respectively. This leg muscle contains exclusively fast-twitch or type II fibers, and before exercise training approximately 40% of these stained intensely for SDH. After 6 and 15 wk training this proportion rose to approximately 50 and 60%, respectively. Most of these highly oxidative fibers also stained weakly for the glycolytic enzyme alpha-glycerophosphate dehydrogenase (alpha-GPDH) and belonged to the fast-twitch oxidative category. Most of the poorly oxidative fibers stained strongly for alpha-GPDH and therefore belonged to the fast-twitch glycolytic category. It is concluded that exercise training in birds can bring about adaptive changes in the oxidative capacity of skeletal muscle similar to those that have been observed in man and other mammals.

Animals↗

Exercise training decreases body fat more in self-selecting than in chow-fed rats.

This study was designed to examine the influence of exercise training on body weight gain and feeding pattern in rats placed on a self-selection or a chow diet regimen. Adult, male, Wistar rats were submitted to daily 2-h treadmill exercise for 28 days (about 50% of VO2 max) at the beginning of the nocturnal period. Two other groups of rats were examined during the same time: a sedentary group that was deprived of food and water during the training session and a control group without any treatment. Food intakes were continuously recorded. For both feeding regimens, trained rats, relative to their respective controls, showed at the end of the experiment a reduction in body weight gain due to a reduced body fat deposit. Moreover, white adipose tissue (WAT) mass of self-selecting rats was smaller than in chow-fed rats. Exercise training decreased plasma glucose level in chow-fed rats and plasma insulin level in self-selecting rats. In self-selecting rats, food intake was slightly increased due to enhanced protein intake during the nocturnal period and fat intake increased both during the nighttime and daytime periods, whereas in chow-fed rats, food intake was decreased during the daytime period. These results show that, in rats placed on a self-selection regimen, exercise training increased fat consumption but reduced WAT. This could be a consequence of an increased lipolytic capacity of adipocytes in self-selecting trained rats. Thus, it appears from these results that the diet's carbohydrate-to-fat ratio can be an important parameter in shaping the interaction between exercise and body weight.

Adipose Tissue↗

Effects of hypocaloric diet and exercise training on inflammation and adipocyte lipolysis in obese postmenopausal women.

The purpose of this study was to determine whether a hypocaloric diet with and without exercise training is effective in reducing plasma C-reactive protein, IL-6, TNFalpha, and their soluble receptors (sIL-6R, sTNFR1, and sTNFR2), and whether changes in these inflammatory markers are related to changes in regional lipolysis in obese (body mass index, 32.78 +/- 4.73) postmenopausal women (diet alone, n = 17; diet plus exercise, n = 17). All inflammatory markers were measured by an ELISA method. In vitro lipolysis was evaluated by measuring glycerol release using a one-step enzymatic fluorometric technique. Six months of diet and diet plus exercise decreased total and abdominal fat to a similar degree. Diet plus exercise, but not diet alone, decreased plasma levels of C-reactive protein, IL-6, sIL-6R, and sTNFR1 and increased basal and postreceptor stimulated lipolysis in both abdominal and gluteal regions. Changes in abdominal stimulated lipolysis correlated significantly with changes in plasma IL-6 (r = -0.39) and TNFR1 (r = -047). Thus, diet plus exercise training, but not diet alone, is effective in reducing chronic inflammation in obese postmenopausal women. In addition, modification of chronic inflammation is associated with changes in local adipose tissue metabolism in response to diet and exercise.

Adipocytes↗

Effects of endurance exercise training on muscle glycogen accumulation in humans.

The purpose of this investigation was to determine whether endurance exercise training increases the ability of human skeletal muscle to accumulate glycogen after exercise. Subjects (4 women and 2 men, 31 +/- 8 yr old) performed high-intensity stationary cycling 3 days/wk and continuous running 3 days/wk for 10 wk. Muscle glycogen concentration was measured after a glycogen-depleting exercise bout before and after endurance training. Muscle glycogen accumulation rate from 15 min to 6 h after exercise was twofold higher (P < 0.05) in the trained than in the untrained state: 10.5 +/- 0.2 and 4.5 +/- 1.3 mmol. kg wet wt(-1). h(-1), respectively. Muscle glycogen concentration was higher (P < 0.05) in the trained than in the untrained state at 15 min, 6 h, and 48 h after exercise. Muscle GLUT-4 content after exercise was twofold higher (P < 0.05) in the trained than in the untrained state (10.7 +/- 1.2 and 4.7 +/- 0.7 optical density units, respectively) and was correlated with muscle glycogen concentration 6 h after exercise (r = 0.64, P < 0.05). Total glycogen synthase activity and the percentage of glycogen synthase I were not significantly different before and after training at 15 min, 6 h, and 48 h after exercise. We conclude that endurance exercise training enhances the capacity of human skeletal muscle to accumulate glycogen after glycogen-depleting exercise.

Adult↗

Physiologic benefits of exercise training in rehabilitation of patients with severe chronic obstructive pulmonary disease.

We determined the effect on exercise tolerance and physiological exercise responses of rigorous rehabilitative exercise training in chronic obstructive pulmonary disease (COPD). Fifteen men and 10 women (mean age, 68 +/- 6 yr; FEV1, 0.93 +/- 0.27 L) participated in a rehabilitation program with an exercise component of three per week 45-min sessions of cycle ergometer training for 6 wk with exercise intensity kept near maximal targets. Before and after rehabilitation, patients performed an incremental test and a constant work rate (CWR) test at 80% of the peak work rate in the preprogram incremental test. Ventilation (V(E)) and gas exchange were measured breath by breath; arterialized venous blood was analyzed for blood gas determinations and lactate. Rehabilitation yielded an average increase in peak work rate in the incremental test of 36% (p < 0.001), and in the duration of the CWR test of 77% (p < 0.001). In the CWR test, the kinetics of O2 uptake, CO2 output, V(E), and heart rate were markedly slower than those of healthy subjects. After training, mean response time decrease averaged 17, 22, 34, and 29%, respectively (p < 0.02), evidence of a physiologic training effect. Further, for identical CWR tasks, V(E) was 10% lower (p < 0.02) after training, attributable to altered breathing pattern: tidal volume increased by 8% and respiratory rate decreased by 19%, yielding lower V(D) /V(T) (0.46 versus 0.53 p < 0.005). Rigorous exercise training for patients with severe COPD yields more efficient exercise breathing pattern and lower V(E); this is associated with improved exercise tolerance.

Aged↗

Effects of exercise training and etidronate treatment on bone mineral density and trabecular bone in ovariectomized rats.

This study was designed to assess the effects of exercise training (Tr) following an etidronate treatment (E) on bone mineral density (BMD) of the femur and trabecular bone of the tibia in ovariectomized (ovx) rats. Female Wistar rats were ovariectomized (ovx) or sham-operated (sham) at 15 weeks of age and divided into five experimental groups: sham; ovx; ovx + E; ovx + Tr; ovx + E + Tr. Etidronate treatment of 5 mg/kg, 5 days/week was administered for 2 weeks and exercised on a treadmill for 30 m/min, 60 min/day, 5 days/week for 10 weeks. BMD of the femur and the trabecular bone area of the proximal tibia were significantly (p < 0.05) higher in E and/or Tr compared to ovx groups. However, the cortical region was not affected significantly by ovariectomy. The area partially filled with the trabecular bone at the constant width was observed only in the E rats. The number of osteoclasts in E group was significantly lower (p < 0.05) than in the ovx and ovx + Tr groups. The ovx + Tr rats had a higher number of osteoblasts (p < 0.05) than the ovx and ovx + E groups. There was a significant interaction between ovx + Tr and ovx + E on BMD in the proximal region of the femur (p < 0.05) and trabecular bone area of the tibia (p < 0.001). These results suggest that the etidronate treatment for 2 weeks beforehand influenced the effects of subsequent exercise training on maintaining the BMD in the proximal femur and the trabecular bone area of the tibia.

Absorptiometry, Photon↗

Reversal of exertional hypotension by prolonged exercise training in selected patients with ischemic heart disease.

The effect of prolonged intense endurance exercise training on exertional hypotension was investigated in 16 patients with coronary artery disease who had a 10 mm Hg or greater fall in systolic blood pressure (SBP) during progressive exercise testing. Training consisted of walking, running, or cycling at 50% to 60% of peak oxygen uptake (peak VO2) for 30 min 3 days per week for an initial 3 months and was followed by an additional 9 months of similar exercise performed at 70% to 90% of peak VO2 for 50 to 60 min 5 days per week. The 1 year program resulted in a 41% increase in peak VO2 and lower heart rate and blood pressure responses to submaximal work. Before conditioning, SBP attained a maximal value of 162 +/- 5 mm Hg but fell 21 +/- 3 mm Hg, to 141 +/- 7 mm Hg, at peak effort (p less than .01). After training, maximal SBP was achieved at a faster heart rate (157 +/- 5 vs 132 +/- 6 beats/min; p less than .001) and was 7.4% higher (174 +/- 6 vs 162 +/- 5 mm Hg; p less than .005), while SBP at peak exercise had increased by 21% (171 +/- 6 vs 141 +/- 7 mm Hg; p less than .001) and ST segment depression was slightly reduced. Left ventricular ejection fraction (LVEF) before training declined from 56 +/- 4% at rest to 52 +/- 3% at peak exercise (p less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Effect of short-term exercise training on insulin-stimulated PI 3-kinase activity in human skeletal muscle.

The purpose of this study was to determine if the improvement in insulin sensitivity with exercise training is associated with enhanced phosphatidylinositol 3-kinase (PI 3-kinase) activity. Nine sedentary men were studied before and after 7 days of exercise training (1 h/day, approximately 75% maximal oxygen consumption). Insulin sensitivity was determined with a euglycemic-hyperinsulinemic glucose clamp in the sedentary state and 15-17 h after the final exercise bout. PI 3-kinase activity was determined from samples (vastus lateralis) obtained in the fasted condition and after 60 min of submaximal insulin stimulation during the clamp. After exercise, glucose infusion rate increased (P < 0. 05) significantly (means +/- SE, 7.8 +/- 0.5 vs. 9.8 +/- 0.8 mg. kg(-1). min(-1)), indicating improved insulin sensitivity. Insulin-stimulated (insulin stimulated/fasting) phosphotyrosine immunoprecipitable PI 3-kinase activity also increased significantly (P < 0.05) with exercise (3.1 +/- 0.8-fold) compared with the sedentary condition (1.3 +/- 0.1-fold). There was no change in fasting PI 3-kinase activity. These data suggest that an enhancement of insulin signal transduction in skeletal muscle may contribute to the improvement in insulin action with exercise.

Adult↗

Effect of exercise training on muscle glucose transporter 4 protein and intramuscular lipid content in elderly men with impaired glucose tolerance.

This study determined the effects of exercise training on adaptations of skeletal muscle including fibre composition, capillarity, intra-muscular triglyceride concentration (IMTG), as well as glucose transporter 4 protein (GLUT4) and metabolic enzyme activities. Percutaneous muscle biopsies from the vastus lateralis muscle were obtained from non-obese elderly Korean men (n = 10; age range 58-67 years) with impaired glucose tolerance. Subjects performed 12 weeks of endurance exercise training (60-70% of the heart rate reserve). The training program improved the total GLUT4 protein expression (P < 0.01), decreased the IMTG, increased the fatty acid oxidation capacity, and the number of capillaries around type 1 fibres (P < 0.05), whereas no significant alteration was observed around type II fibres. All data are presented as the means together with the standard deviation. The results suggest that endurance training evokes morphological and biochemical changes in the skeletal muscle of elderly men with impaired glucose tolerance that may be considered to limit the development of type 2 diabetes.

Adaptation, Physiological↗