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At least 919 records · Page 51Linked to original sources
PubMed1982

[Electron microscope study of skeletal muscle fibers during physical exercise in high-altitude hypoxia].

Experiments on rats exposed to intense exercise and high-altitude hypoxia have shown the reduction in physical efficiency and in the training effect of muscle loads as compared to the same characteristics examined under the conditions of plain. Electron microscopy of rat skeletal muscle fibers has discovered significant changes in their ultrastructure. Morphometric analysis of the same changes has shown a reduction in the relative volume of mitochondria, an increase in the relative volume of sarcoplasmic reticulum an abrupt fall of the glycogen reserves in the early stages of experiment with a further tendency towards the normalization of this characteristic. The changes described were followed by focal destructive-degenerative abnormalities in the energy and in the contractile-myofibrillar apparatuses.

Adaptation, Physiological↗
PubMed1993

Renin-angiotensin-aldosterone system and physical exercise.

The renin-angiotensin-aldosterone system plays a primary role in regulating the physiological response and adaptation of fluid-electrolyte balance as well as cardiovascular function to exercise in man. We reviewed the main mechanisms leading to stimulation of the renin-angiotensin-aldosterone axis during physical stress, i.e. the decrease in renal perfusion and in the NaCl load to the macula densa, the enhancement of sympathetic activity, and the reduction in hormone clearance rate. Interpretation of hormonal changes is difficult because of the variability in environmental conditions and exercise protocols, and the different subjects characteristics. We analyzed these confounding variables reported in literature studies, showing their influence on renin-angiotensin-aldosterone response. Possible implications of these hormonal alterations for performance and health, and the evaluation of new mechanisms of hormones regulation, i.e. receptor changes, require further research.

Adaptation, Physiological↗
PubMed1979

Adjustments of circulation including blood pressure to orthostatic reaction and physical exercise during application of a low estrogen dose steroid oral contraceptive.

The orthostatic circulatory reaction, the physical working capacity on a bicycle ergometer, the blood pressure reactions at rest both during and after the ergometer test, the total hemoglobin content and the heart volume in the supine position were all determined on four separate occasions in 34 nulligravidae who were taking a low estrogen dose steroid oral contraceptive consisting of 30 micrograms of ethinyl estradiol and 150 micrograms of levonorgestrel (known as Neovletta, Schering AG). These examinations were performed once prior to the commencement of this medication, and 6, 12 and 24 months thereafter. The orthostatic pulse and blood pressure reactions taken on these subjects standing upright for a period of eight minutes were pronounced up to and including the 12 month control, but decreased thereafter. Physical working capacity at a pulse rate of 170 beats per minute on the different test occasions decreased up to and including the 12 month control, but thereafter seemed to increase almost to their initial levels. Blood pressure, heart volume and total amount of hemoglobin increased up to and including the 12 month control but thereafter seemed to return to the pre-treatment level. These circulatory changes during the first year of the application of this contraceptive may be as the result of a marked sympathicotonic reaction induced by the steroids. Possibly because of some form of adaptive mechanism, this reaction seems to decrease (and almost to "normalize") during the second year of use.

Adolescent↗
PubMedDate not supplied

[The effect of the combination of vitamin E and C on the oxidative stress parameters in physical exercise].

The paper outlines the modification of some antioxidant enzymes and of reduced glutathione studied on physical training induced oxidative stress model. We also assessed vitamin E and C effect. Biochemical determinations were performed on heart homogenate and erythrocytes. Catalase and glutathione peroxidase activity diminished and superoxide dismutase activity increased to a different extent in both tissue samples, while coupled vitamin E and C protection to these tissues equally varied. The glutathione (GSH) pool decreased in erythrocytes and was moderately enhanced in the heart. Either in red blood cells or heart tissue GSH level constancy was maintained by simultaneous administration of vitamins through the experiment (training period). Malondialdehyde concentration revealed a slightly pro-oxidative behaviour of this couple of vitamins that explained the only partial recovery of enzymatic activity to normal values as well as a moderate lipid peroxidation process. Both phenomena were better expressed in erythrocytes.

Animals↗
PubMed1991

[Effects of antidepressive agents on tolerance of hypoxia and physical exercise].

In experiments on mice and rats we studied the influence of antidepressants on hypoxic and physical tolerance. The antidepressants pyrazidol, azaphen, imipramine and moclobemide as well as the nootropic drug piracetam prolonged the life of animals in conditions of hypoxic and hemic hypoxia and increased the survival rate of rats in circulatory hypoxia. In experiments on mice antidepressants increased also the time of swimming.

Animals↗
PubMed1995

Metabolic effects of atenolol and doxazosin in healthy volunteers during prolonged physical exercise.

Nonselective beta-blockers may reduce exercise performance, not only through hemodynamic but also through metabolic effects. During prolonged physical exertion, lipolysis induced by plasma epinephrine occurs through beta-adrenoceptors of adipocytes. Therefore, beta-blockade may reduce release of free fatty acids (FFA) from adipocytes and consequently the energy supply for muscle cells. In this single-blind study, we compared the metabolic effects of atenolol with those of doxazosin, an alpha 1-blocker, during exercise in 26 young volunteers (age 20-35 years). All subjects performed an exercise test on a bicycle ergometer 5 h after consuming a standard breakfast. The starting workload of 50 W was increased by 30 W every 3 min until maximal heart rate (HR) was achieved; after a 2-min recovery period at 50 W the test was continued for 15 min at 60% maximal workload. Before and at the end of the test, blood samples were taken for glucose, lactate, and FFA determination. After 1 week, the test was repeated; the volunteers randomly received atenolol or doxazosin for 2 days before the second test. Exercise performance, plasma glucose, and lactate were not affected by either drug. The concentration of FFA was unchanged in subjects treated with doxazosin but was significantly reduced after the test in subjects treated with atenolol. Our data demonstrate that neither doxazosin nor atenolol impairs exercise performance in young volunteers. Atenolol reduces plasma FFA concentration possibly by inhibiting lipolysis. Doxazosin, in contrast, does not alter this parameter. Therefore, doxazosin may be a antihypertensive drug of potential benefit in treatment of hypertensive patients engaging in sports or undergoing a program of physical training.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1992

[Echocardiographic evaluation of the left ventricle in mild hypertension treated with physical exercise].

The authors submit findings of haemodynamic changes during long-term treatment of mild hypertension by physical training. Using this method, blood pressure was normalized in all subjects. The authors conclude that physical activity has a similar impact on the haemodynamics of mild hypertension as drugs which reduce the tension of the sympathetic nerve. A surprising finding was the diminution or complete disappearance of cardiac hypertrophy in this treatment.

Adult↗
PubMed1999

[Effects of physical exercise on the cardiorespiratory system in children].

OBJECTIVE: Our aim was to perform a prospective study to evaluate the effects of competitive sports on the cardiorespiratory system and physical performance in children. PATIENTS AND METHODS: Male children aged 6 and 7 years were selected from a public school (PS) and from a soccer sports school (SS). They underwent anthropometrical measurement. Those boys who were further than one standard deviation from the 50th percentile were excluded from the study. A total of 74 boys were selected with 41 being from the PS and 33 from the SS. Three different physical competitive activities were performed by the children. Hemodynamic measurements [heart rate (HR), systolic, mean and diastolic blood pressure (SBP, MBP and DBP)] and respiratory measurements [respiratory rate (RR), arterial oxygen saturation (SatO2), peak expiratory flow (PEF), forced expiratory volume in one second (FEV1), forced vital capacity (FVC), and the FEV1/FVC relationship] were taken before and after the physical activity. RESULTS: Overall we found a significantly higher physical performance in the SS group (p < 0.001). The HR before and after exercise was significantly lower in the SS group. The comparison between constants before and after physical activity in each group showed a significant increase in HR, SBP, MBP and DBP in the PS group, but there was no difference between the SBP before and after physical activity in the SS group. The SS group had a significantly lower RR and better SatO2 in the basal measurement. The relationship between constants before and after physical activity showed a rise in the PEF in the PS group and a decrease in the SatO2 in the SS group. CONCLUSIONS: We recommend controlled physical competitive activity in children because of its benefits on cardiorespiratory function and the absence of adverse effects.

Anthropometry↗
PubMed1999

Effects of physical exercise in pre-and postmenopausal women on lipid peroxidation and antioxidant systems.

The effects of moderate physical activity were studied in 19 postmenopausal and 25 premenopausal women on the enzymatic (superoxide dismutase and catalase) and non-enzymatic (vitamins A and E) antioxidant systems and on the processes of lipid peroxidation (malondialdehyde), and to see whether there is any variation in oxidative stress indicators between the postmenopausal and non-menopausal women. The subjects were also studied anthropometrically. At the end of a training period, there was a decrease in body fat percentage and in various skin folds. Neither group presented a rise in lipid peroxidation levels, although there was a significant (p<0.05) rise in superoxide dismutase activity in the postmenopausal women.

Adult↗
PubMed1994

Physical exercise and psychological health.

For individuals who are just beginning to exercise, the very unfit, the elderly and persons suffering from psychiatric disorders, low intensity activity has important potential psychological benefits. Several studies indicate that mental health can be improved by low- or moderate-intensity activity. In 2 studies it could be demonstrated that aerobic exercise plus counselling was more effective in the treatment of depressive disorders than counselling alone. Cross-sectional community studies clearly reveal that after controlling for potential sociodemographic and health-related confounding variables the risk of depression is significantly higher for physically inactive individuals compared with regular exercisers. No final conclusions can be drawn from longitudinal field studies on the predictive value of physical activity on the degree of depressive symptoms. Several biological and psychological hypotheses have been proposed to explain the association between physical activity and mental health, however, there is still a lack of an integrated theoretical model.

Exercise↗
PubMed1985

Plasma testosterone and catecholamine responses to physical exercise of different intensities in men.

Plasma testosterone, noradrenaline, and adrenaline concentrations during three bicycle ergometer tests of the same total work output (2160 J X kg-1) but different intensity and duration were measured in healthy male subjects. Tests A and B consisted of three consecutive exercise bouts, lasting 6 min each, of either increasing (1.5, 2.0, 2.5 W X kg-1) or constant (2.0, 2.0, 2.0 W X kg-1) work loads, respectively. In test C the subjects performed two exercise bouts each lasting 4.5 min, with work loads of 4.0 W X kg-1. All the exercise bouts were separated by 1-min periods of rest. Exercise B of constant low intensity resulted only in a small increase in plasma noradrenaline concentration. Exercise A of graded intensity caused an increase in both catecholamine levels, whereas, during the most intensive exercise C, significant elevations in plasma noradrenaline, adrenaline and testosterone concentrations occurred. A significant positive correlation was obtained between the mean value of plasma testosterone and that of adrenaline as well as noradrenaline during exercise. It is concluded that both plasma testosterone and catecholamine responses to physical effort depend more on work intensity than on work duration or total work output.

Adult↗
PubMed1998

Attenuated physical exercise capacity in smokers compared with non-smokers after coronary angioplasty despite similar luminal diameters.

AIMS: To study the impact of smoking on the change in exercise capacity in patients treated with coronary angioplasty. METHODS: Three hundred and sixty-eight men below 70 years of age eligible for percutaneous transluminal coronary angioplasty without previous coronary interventions were consecutively enrolled. Of the 334 patients (90.8%) who completed the study 77 (23.1%) were current smokers. Exercise tests were performed before percutaneous transluminal coronary angioplasty, 2 and 19 +/- 2.4 weeks after percutaneous transluminal coronary angioplasty. Coronary angiography was done in 333 patients (99.7%) (at mean 19 +/- 2.4 weeks). The angiograms were analysed quantitatively. RESULTS: There were no differences in the clinical and angiographic characteristics among the groups except for age. The non-smokers were older than the smokers (55.7 vs 52.4 years (P = 0.001)). Exercise capacity was equal before percutaneous transluminal coronary angioplasty in both groups (17.6 vs 16.5 W x min-1 x kg-1). Non-smokers had a significantly higher increase in exercise capacity than smokers from baseline to 2 weeks after percutaneous transluminal coronary angioplasty (mean difference 4.3 W x min-1 x kg-1 (95% CI: 2.3 to 6.2; P < 0.001)), and from baseline to 19 weeks after percutaneous transluminal coronary angioplasty (mean difference 3.9 W x min-1 x kg-1 (95% CI: 1.6 to 6.2; P < 0.001). CONCLUSION: A clinical benefit from percutaneous transluminal coronary angioplasty was seen in both groups as judged from exercise testing. Smokers had a substantially lower increase in exercise capacity than non-smokers, indicating an attenuated benefit from percutaneous transluminal coronary angioplasty among smokers.

Adult↗
PubMed1986

Free and conjugated catecholamines in human plasma during physical exercise.

To investigate changes of free and sulfoconjugated catecholamines in response to alterations in sympatho-adrenal activity, free and conjugated noradrenaline, adrenaline and dopamine were determined radioenzymatically in plasma of 49 subjects. During brief vigorous bicycle exercise (8 min, maximal heart rate: 177 beats/min) mean free noradrenaline and adrenaline values of 2.0 and 0.51 nmol/l at rest, increased to 6.7 and 2 nmol/l (P less than 0.001) respectively, at the maximal workload of 200 watt, whereas conjugated noradrenaline and adrenaline decreased from 3.4 and 0.8 nmol/l to 2.1 and 0.4 nmol/l (P less than 0.001) respectively. In the tenth min of the recovery period basal free and conjugated noradrenaline and adrenaline levels were measured. The moderate stress of a steam bath (20 min, maximal heart rate: 131 beats/min) doubled free noradrenaline and adrenaline levels. However, conjugated noradrenaline and adrenaline concentrations remained unchanged. The increase in free catecholamine values during an exhausting cross-country march over 20 km was associated with an accumulation of sulfated catecholamines. After a rest of 30 min free noradrenaline and adrenaline reached basal values, whereas conjugated noradrenaline and adrenaline remained elevated by 64 and 70% respectively, compared to pre-exercise concentrations. It was concluded that conjugated noradrenaline and adrenaline may be used as pools for free noradrenaline and adrenaline during brief vigorous exercise. In addition, they may also be indicators of chronic activation of the sympatho-adrenal system.

Adult↗
PubMed2002

Physical exercise and blood pressure with reference to the angiotensinogen M235T polymorphism.

We investigated the role of the angiotensinogen (AGT) gene M235T polymorphism in determining blood pressure (BP) response to moderate intensity exercise in a 6-yr randomized controlled trial in 140 middle-aged men. Sitting, supine, and standing blood pressures were measured annually. Of the randomized men, 86% participated in the trial for 6 yr. Submaximal cardiorespiratory fitness increased by 16% in the exercise group. In the M homozygotes, sitting systolic BP decreased by 1.0 mmHg in the exercise but increased by 14.6 mmHg in the reference group (P = 0.007 for net effect). Sitting and supine diastolic BP decreased by 6.2 and 3.3 mmHg in the exercise but increased by 2.8 and 3.2 mmHg in the reference group (P = 0.026 and 0.024 for net effects), respectively. Regular moderate intensity exercise attenuates aging-related increase in systolic BP and decreases diastolic BP among the M homozygotes of the AGT gene M235T polymorphism.

Aging↗