Search Results
Results 451 - 500 of 821
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Bosquet L - - 2003
AIM: The purpose of the study was to examine whether an unaccustomed increase in training volume would result in characteristics changes in heart rate variability (HRV), in order to determine if this marker can be used to diagnose overtraining. METHODS: Nine experienced endurance athletes increased their usual amount of training ...
Arlt Josef - - 2003
BACKGROUND: Heart rate variability represents a reliable marker to delineate the status of autonomic nervous system (ANS) function and alterations due to stress in vivo. Interestingly, up to now the effects of corticotropin-releasing hormone (CRH), a key regulator of the stress hormone system, upon heart rate variability are not sufficiently ...
Kaya Dayimi - - 2003
AIM: Long-term estrogen replacement therapy has favorable results on autonomic cardiovascular functions in postmenopausal women. Although acute estrogen administration has beneficial modulations on autonomic tone in animal studies, there are still controversies about the effects of acute estrogen on autonomic modulation to the heart in humans. The aim of this ...
Dingli K - - 2003
A recent study has shown that daytime heart rate variability is reduced in obstructive sleep apnoea/hypopnoea syndrome (OSAHS) patients. In the present study, the hypothesis was that sympathovagal balance around apnoeas/hypopnoeas and nocturnal autonomic activity are altered in OSAHS patients. Frequency- and time-domain analyses of RR intervals were performed to ...
Welzig C Michael - - 2003
We have previously demonstrated in an in vitro model for lipid lowering that lipoprotein depletion resulted in a marked increase in the negative chronotropic response to the acetylcholine analogue carbamylcholine. In this study we used heart rate variability analysis to determine the effect of lipid lowering by statins on the ...
García-González M A - - 2003
A new index for the analysis of the heart rate variability (HRV) dynamics is presented. The proposed index (acceleration change index (ACI)) characterizes the sign of the differences of a time series. A theoretical study shows an expression that relates ACI and the autocorrelation function of the time series. This ...
Agostoni Piergiuseppe - - 2003
BACKGROUND: In heart failure (HF) patients, exercise may increase pulmonary capillary hydrostatic pressure and thereby generate pulmonary edema. If pulmonary edema developed, alveolar-capillary membrane conductance (Dm), measured immediately after exercise, would decrease. To test this hypothesis, we measured Dm before and at 2 and 60 minutes after exercise. METHODS AND ...
Charkoudian Nisha - - 2003
Dehydration is known to decrease orthostatic tolerance and cause tachycardia, but little is known about the cardiovascular control mechanisms involved. To test the hypothesis that arterial baroreflex sensitivity increases during exercise-induced dehydration, we assessed arterial baroreflex responsiveness in 13 healthy subjects (protocol 1) at baseline (PRE-EX) and 1 h after ...
Cottin François - - 2004
This study compared heart rate variability (HRV) in ten male judokas between two types of exercise eliciting the same near-maximal average heart rate (HR): judo wrestling vs. cycloergometric bout. Beat-to-beat RR intervals were recorded during (1) a 4-min judo randori (wrestling); (2) a 4-min cycloergometric exercise eliciting maximal oxygen consumption ...
Perini Renza - - 2003
The rhythmic components of heart rate variability (HRV) can be separated and quantitatively assessed by means of power spectral analysis. The powers of high frequency (HF) and low frequency (LF) components of HRV have been shown to estimate cardiac vagal and sympathetic activities. The reliability of these spectral indices, as ...
Mourot Laurent - - 2004
The aim of the study was to evaluate the effectiveness of the Poincaré plot analysis of heart rate variability (HRV) in observing endurance training-induced changes. Four 10-min manoeuvres were performed (supine lying, standing, steady state exercising and subsequent recovery) by eight control subjects before and after a short-term endurance training ...
Brubaker Peter H - - 2003
PURPOSE: Little information is available regarding peak and submaximal exercise performance in elderly heart failure (HF) patients, particularly in those with diastolic dysfunction (DD). Therefore, the purpose of this investigation was to compare exercise responses of elderly patients with HF due to either systolic dysfunction (SD) or DD, to age-matched ...
Bartels Matthew N - - 2003
STUDY OBJECTIVES: To evaluate cardiac autonomic modulation in patients with COPD during peak exercise. METHODS: Fifty-three patients with COPD (mean FEV(1), 35% predicted [SD, 11% predicted]; mean PaO(2), 68 mm Hg [SD, 11 mm Hg]; mean PaCO(2), 40 mm Hg [SD, 7 mm Hg]; mean age, 61 years [SD, 10 ...
Stanfill Amber A - - 2003
This study examined the role of leucine-enkephalin (LE) in the sympathetic regulation of the cardiac pacemaker. LE was administered by microdialysis into the interstitium of the canine sinoatrial node during either sympathetic nerve stimulation or norepinephrine infusion. In study one, the right cardiac sympathetic nerves were isolated as they exit ...
Lucy S Deborah - - 2003
Supine resting cardiac dynamics and responses to steady-state hypoxemia were investigated in six healthy older (59-72 yrs) adults using coarse-graining spectral analysis of heart rate variability (HRV) and were compared to six young (22-29 yrs) adults studied previously (Lucy et al., 2000). End-tidal carbon dioxide pressure (PETCO2) was clamped at ...
Loimaala Antti - - 2003
Type 2 diabetes is a strong risk factor for coronary heart disease and sudden cardiac death. It is associated with reduced baroreflex sensitivity (BRS) and heart rate variability (HRV), which are indicators of increased risk for mortality and morbidity in various patient populations. This study was designed to assess the ...
Reland Sylvia - - 2003
The purpose of this study was to determine the effect of the level of physical activity in older women on heart rate (HR) response to its neural control at rest and during exercise by using heart rate variability (HRV) analysis. Electrocardiogram (ECG) was recorded in 3 (low, moderately, and highly) ...
Naritoku Dean K - - 2003
PURPOSE: Human epilepsy is associated with abnormalities in cardiac regulation, as measured by reductions of heart rate variability (HRV) and approximate entropy (ApEn), but it is not known how these abnormalities are related to seizure experience. METHODS: Baseline electrocardiogram (ECG) was recorded from seizure-naive rats. They were subjected daily to ...
Chiu Hung-Wen - - 2003
Some studies have demonstrated that the assessments of autonomic activities from the alterations of heart rate variations (HRVs) after autonomic blockade and during exercise of high intensity by the spectral analysis of HRV seemed inconsistent with actual situation. The inconsistency is probably caused by the contributions of fluctuating magnitudes and ...
Hautala Arto J - - 2003
Individual responses to aerobic training vary from almost none to a 40% increase in aerobic fitness in sedentary subjects. The reasons for these differences in the training response are not well known. We hypothesized that baseline cardiovascular autonomic function may influence the training response. The study population included sedentary male ...
Beckers F - - 2003
During parabolic flight short periods of microgravity and hypergravity are created. These changes influence cardiovascular function differently according to posture. During the 29th parabolic flight campaign of the European Space Agency (ESA), the electrocardiogram (ECG) was recorded continuously in seven healthy volunteers in two positions (standing and supine). Five different ...
Lee C Matthew - - 2003
PURPOSE: To examine the influence of 2 wk (eight sessions) of endurance training on cardiac autonomic modulation, as measured by heart rate variability (HRV). METHODS: Twenty-four males (mean age: 23.1 yr) were randomized to an exercise (EX; N = 12) or control group (CT; N = 12). EX trained for ...
Leicht Anthony S - - 2003
The purpose of this study was to examine the influence of age and moderate-intensity exercise training on heart rate variability (HRV), and to elucidate further the mechanism of training-induced bradycardia and cardioprotection. Electrocardiograms were recorded from 12 young (18-24 yrs) and 12 mature (29-43 yrs) individuals during supine rest and ...
Woodman Christopher R - - 2003
We tested the hypothesis that exercise training (Ex) attenuates the effects of hyperlipidemia on endothelial function by enhancing NO-mediated vasorelaxation in porcine brachial (Br) arteries. Adult female pigs were fed a normal-fat (NF) or high-fat (HF) diet for 20 wk. Four weeks after initiation of the diet, pigs underwent Ex ...
Jáuregui-Renaud Kathrine K Unidad de Investigación Medica, Hospital General, Centro Medico Nacional La Raza, Instituto Mexicano del Seguro Social, Mexico City, Mexico. - - 2003
Experimental work indicates that the vestibular system participates in autonomic reflexes during body movement and postural changes. However, there are no studies of cardiovascular reflexes during vertigo due to human acute vestibular lesions. We assessed the response to active change of posture and hand immersion in cold water in seven ...
Dela Flemming - - 2003
BACKGROUND: We studied the role of the central nervous system, neural feedback from contracting skeletal muscles, and sympathetic activity to the heart in the control of heart rate and blood pressure during 2 levels of dynamic exercise. METHODS AND RESULTS: Spinal cord-injured individuals (SCI) with (paraplegia, n=4) or without (tetraplegia, ...
Straube Thomas - - 2003
Long-term potentiation (LTP) in the hippocampus of awake animals is known to be reversed by long trains of low-frequency stimulation (LFS). Here we show that a persistent LTP reversal, i.e. depotentiation (DP), can be induced in the dentate gyrus of freely moving rats by brief 7 Hz stimulations (three trains ...
Balt Jippe C - - 2003
Both in human and in experimental heart failure (HF), the renin-angiotensin system and the sympathetic nervous system are activated. In a previous study a facilitatory action of angiotensin II (Ang II) was shown in the rabbit mesenteric artery, which was mediated via prejunctionally located Ang II type 1 (AT ) ...
Ueno Linda Massako - - 2003
Reductions in tonic vagal controls of the heart and depressed baroreflex sensitivity (BRS) have been associated with a postural fall in blood pressure (BP) and the incidence of cardiac events among older people. We examined the hypothesis that BP regulation during orthostatic challenge as well as heart rate variability (HRV) ...
Yamamoto Yoshiharu - - 2003
The use of symptoms generated by head up tilt (HUT) is not a useful tool in identifying chronic fatigue syndrome (CFS). We investigated whether heart rate variability (HRV) assessed early during HUT might be useful. A sample of 46 female subjects (24 with CFS and 22 sedentary, age-matched healthy controls; ...
Facchini M - - 2003
The autonomic control of the heart is abnormal in obese subjects due to a prevalence of sympathetic over parasympathetic limb of the autonomic balance. We evaluated the effects of a short-term (3 weeks) integrated body weight reduction program (consisting of energy restricted diet and high-intensity exercise training) on heart rate ...
Zenon Gawor - - 2003
Heart rate variability is a widely used method to evaluate vagal and sympathetic influences on the heart. The purpose of this study was to assess the relationship of autonomic nervous system components' interaction in supersonic fighter pilots by means of a sinus rhythm variability analysis. The following frequency domain parameters ...
Migeotte P-F - - 2003
We studied heart rate (HR), heart rate variability (HRV), and respiratory sinus arrhythmia (RSA) in four male subjects before, during, and after 16 days of spaceflight. The electrocardiogram and respiration were recorded during two periods of 4 min controlled breathing at 7.5 and 15 breaths/min in standing and supine postures ...
Forte Roberta - - 2003
Twenty healthy women aged between 65 and 74 years, trained three times a week, for 16 weeks, on a cycle ergometer, to determine the effects of dynamic resistance training on heart rate variability (HRV). Subjects were allocated to two training groups, high (HI, n=10) and low (LO, n=10) intensity. The ...
Udupa Kaviraja - - 2003
Systolic time intervals (STI) are non-invasive and sensitive tests for measuring the ventricular performance. It has been reported that practice of pranayam modulates cardiac autonomic status and improves cardio-respiratory functions. Keeping this in view, the present study was designed to determine whether pranayam training has any effect on ventricular performance ...
Honzíková N - - 2003
The correlation between baroreflex sensitivity (BRS) and the spectrum component at a frequency of 0.1 Hz of pulse intervals (PI) and systolic blood pressure (SBP) was studied. SBP and PI of 51 subjects were recorded beat-to-beat at rest (3 min), during exercise (0.5 W/kg of body weight, 9 min), and ...
Miller Michael - - 2003
Superimposed electrical stimulation techniques can be used to detect central activation failure (CAF), that is, incomplete central nervous system recruitment or suboptimal activation of motor units. The purpose of this study was to evaluate the effects of two stimulation parameters on perceived discomfort and torque increment size and variability. Discomfort ...
Barclay Linda - - 2003
In this paper I argue that the genetic manipulation of sexual orientation at the embryo stage could have a detrimental effect on the subsequent person's later capacity for autonomous agency. By focussing on an example of sexist oppression I show that the norms and expectations expressed with this type of ...
Carter James B - - 2003
Long-term endurance training significantly influences how the autonomic nervous system controls heart function. Endurance training increases parasympathetic activity and decreases sympathetic activity in the human heart at rest. These two training-induced autonomic effects, coupled with a possible reduction in intrinsic heart rate, decrease resting heart rate. Long-term endurance training also ...
Katoh Kansei - - 2003
BACKGROUND: Activation of glucagon receptors of the smooth muscle membrane suppresses gastric peristalsis. We evaluated autonomic nervous activity by two methods, electrogastrography (EGG) and analysis of heart rate variability, to compare the inhibiting effects of glucagon and scopolamine butylbromide on gastric peristalsis. METHODS: Heart rate variability, EGG, and blood catecholamine ...
Aubert André E - - 2003
This review examines the influence on heart rate variability (HRV) indices in athletes from training status, different types of exercise training, sex and ageing, presented from both cross-sectional and longitudinal studies. The predictability of HRV in over-training, athletic condition and athletic performance is also included. Finally, some recommendations concerning the ...
Souza-Rabbo Maristela P - - 2003
The present study investigated the influence of different frequencies of moderate exercise (13 weeks of treadmill running at 60% of maximal oxygen consumption) on oxidative stress in the heart and liver in rats. Oxidative stress was evaluated by chemiluminescence and lipid peroxidation (LPO) through thiobarbituric acid reactive substances. Activities of ...
Fries Roland - - 2002
BACKGROUND: It is generally supposed that diurnal fluctuations of heart rate variability (HRV) are associated with diurnal variability of occurrence of sudden cardiac death, usually caused by tachyarrhythmias. To date, however, there have been no data comparing circadian rhythms of HRV and circadian variability of malignant ventricular tachyarrhythmias in the ...
Roussel M - - 2003
Onset of intracellular acidosis during muscular exercise has been generally attributed to activation or hyperactivation of nonoxidative ATP production but has not been analyzed quantitatively in terms of H(+) balance, i.e., production and removal mechanisms. To address this issue, we have analyzed the relation of intracellular acidosis to H(+) balance ...
Pichot Vincent - - 2002
PURPOSE: Looking for practical and reliable markers of fatigue is of particular interest in elite sports. One possible marker might be the autonomic nervous system activity, known to be well affected by physical exercise and that can be easily assessed by heart rate variability. METHODS: We designed a laboratory study ...
Sica Anthony L - - 2002
The hypothesis that hypercapnia-induced differences in heart rate variability (HRV) would emerge during early maturation was tested using a developing porcine model. Piglets were randomly assigned to either exposed (10% CO2 for 1 h) or control (100% O2) conditions, and then to one of three study groups: (a) 5-8 days ...
Herbert Rowan W L - - 2002
The aim of this study was to examine the influence of 20 min of hard exercise (HR>160 beats min(-1)) on the efficacy of the cardiac parasympathetic nervous control of heart rate in humans (20-31 years; of either sex). This intensity of exercise was chosen to produce strong activation of the ...
Ueno Linda Massako - - 2002
BACKGROUND: Aging associated changes in sympatho-vagal activities have been widely studied. However, little is known about the association between cardiorespiratory fitness level and cardiac autonomic nervous activities in conjunction with baroreflex sensitivity in healthy older men. METHODS: We performed an incremental submaximal exercise test in 24 healthy, older men aged ...
Schneider Suzanne M - - 2002
PURPOSE: Supine, moderate exercise is ineffective in maintaining orthostatic tolerance after bed rest (BR). Our purpose was to test the hypothesis that adding an orthostatic stress during exercise would maintain orthostatic function after BR. METHODS: Seven healthy men completed duplicate 15-d 6 degrees head-down tilt BR using a crossover design. ...
Elstad Maja - - 2002
We have tested whether the cardiovascular changes at the onset of exercise could be simulated only by an increase in the baroreflex set point and locally induced vasodilatation in the exercising muscles. The mathematical model consists of a heart, a linear elastic arterial reservoir and two parallel resistive vascular beds. ...
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