Increases in cadence may augment SV during submaximal cycling (> 65 % VO2max) via effects of increased muscle pump activity on preload. At lower workloads (45 - 65 % VO2max), SV tends to plateau, suggesting that effects of increases in cadence on pump activity have little influence on SV. We ...

We tested the hypotheses that women completing 56 days, 6 degrees head-down bed-rest (HDBR) would have changes in sensitivity of cardiovascular responses to adrenergic receptor stimulation and that frequent aerobic and resistive exercise would prevent these changes. Twenty-four women, eight controls, eight exercisers (lower body negative pressure treadmill and flywheel ...

The ageing process has the potential to impact upon the manner in which an athlete responds to training stimuli. This study investigated if power output (PO) and heart rate (HR) at the modified D-max lactate transition threshold (D-max) was comparable with the mean HR and power that could be sustained ...

PURPOSE: To evaluate the effect, and the duration of the effect, of topically administrated travoprost and unoprostone on optic nerve head (ONH) circulation in Dutch rabbits. METHODS: First, travoprost (0.004% solution) or unoprostone (0.12% solution) was unilaterally instilled once, or once daily (travoprost) or twice daily (unoprostone) for 7 days ...

We tested the validity of an new methodological approach to the calculation of oxygen uptake efficiency slope (OUES) [i.e. the use of exercise end-points based on fractions of heart rate reserve (HR(res))], as an alternative to the traditional time-based calculation. Twenty-nine healthy sedentaries >60 years of age (18 males, 11 ...

This study assessed whether the accuracy of predicting maximal oxygen uptake (VO2max) from sub-maximal heart rate (HR) and ratings of perceived exertion (RPE) values was moderated by gender and habitual activity. In total, 27 men and 18 women completed two GXTs to determine VO2max and three perceptually-regulated GXTs, incremented by ...

Patients with postural tachycardia syndrome (POTS) have excessive tachycardia without hypotension during orthostasis as well as exercise. We tested the hypothesis that excessive tachycardia during exercise in POTS is not related to abnormal baroreflex control of heart rate (HR). Patients (n = 13) and healthy controls (n = 10) performed ...

The purpose of this study was to quantify intermittent training sessions using different types of exercise. Strength, sprint, and endurance sessions were performed until exhaustion. These sessions were quantified by the product of duration and heart rate (HR) (i.e., training impulse (TRIMP) and HR-zone methods), by the product of duration ...

Postural tachycardia syndrome (POTS) is characterized by excessive tachycardia without hypotension during orthostasis. Most POTS patients also report exercise intolerance. To assess cardiovascular regulation during exercise in POTS, patients (n = 13) and healthy controls (n = 10) performed graded cycle exercise at 25, 50, and 75 W in both ...

Many fish species adapt to hypoxia by reducing their metabolic rate and increasing hemoglobin-oxygen (Hb-O(2)) affinity. Pilot studies with young broods of cichlids showed that the young could survive severe hypoxia in contrast with the adults. It was therefore hypothesized that early exposure results in improved oxygen transport. This hypothesis ...

In general, cardiac regulation is dominated by the sympathetic and parasympathetic nervous systems in men and women, respectively. Our recent study had revealed sex differences in the forebrain network associated with sympathoexcitatory response to baroreceptor unloading. The present study further examined the sex differences in forebrain modulation of cardiovagal response ...

Passive postexercise heart rate (HR) recovery is currently used in the assessment of endurance athletes to determine changes in performance or in the clinical setting as a predictor of all-cause mortality. The purpose of this investigation was to assess the reliability of HR recovery. Thirty healthy subjects performed two maximal ...

BACKGROUND: Abnormal exercise-related heart rate (HR) dynamics, that is, blunted exercise HR response, lower peak HR, and delayed HR recovery after exercise, are associated with high morbidity and mortality in adults with acquired and congenital heart disease (CHD). However, the precise mechanisms underlying the abnormal HR dynamics remain unclear. OBJECTIVES: ...

Embryos of the annual killifish Austrofundulus limnaeus can experience oxygen deprivation as part of their normal developmental environment. We exposed embryos to anoxia and monitored heart activity for 48 hr, and subsequent aerobic recovery from anoxia for 40 hr. Embryos were tested at four different developmental stages that differ in ...

We sought to examine the influence of exercise intensity on carotid baroreflex (CBR) control of heart rate (HR) and mean arterial pressure (MAP) at the onset of exercise in humans. To accomplish this, eight subjects performed multiple 1-min bouts of isometric handgrip (HG) exercise at 15, 30, 45 and 60% ...

This study examined cardiovascular responses as a function of time following exercise in which participants were exposed to a laboratory stressor. Ninety (42 women) young (18-35 years old) nonsmoking normotensive participants engaged in 30 min of high and low intensity (75-80% and 50-55% VO(2) max) aerobic exercise and a sedentary ...

OBJECTIVES: Heart rate (HR) accelerates with the electroconvulsive therapy (ECT) seizure and decelerates when it ends. The peak HR during ECT seizure has been reported to reflect clinical impact. We aimed to identify the expected range for ECT peak HR and how it varies with age and sex, as a ...

Load carriage is a key element in dismounted military operations. Load carriage requirements in the field regularly exceed 50% of lean body mass (LBM) and have only rarely been studied. Therefore, our purpose was to determine the metabolic and motivational effects of heavy loads (30-70% LBM) during constant-rate "road" marching ...

OBJECTIVE: Vehicular speeds have been identified to be at the core of road accident severity and frequency globally. Whereas speed control is a fundamental priority and the cornerstone of road safety in the developed world, the subject is at rudimentary stages in most developing countries thus making research into vehicle ...

We assessed heart rate (HR) recovery following peak exercise before and after a 12-week cardiac rehabilitation program in 14 children, 12.1+/-1.8 years of age, with repaired complex congenital heart disease (CHD; 11 with Fontan surgery) and impaired exercise performance. Exercise testing using bicycle ergometry was performed at baseline, after completion ...

BACKGROUND: Peripheral arterial disease (PAD) is a risk factor for cardiovascular events. This study assessed the prognostic significance of repeated ankle-brachial index (ABI) measurements at rest and after exercise in patients with PAD receiving conservative treatment. METHODS: In a cohort study of 606 patients (mean age 62+/-12 years, 68% male), ...

Recent evidence supports the use of certain soccer drills for combined technical and physical training. Therefore, it is important to be able to accurately monitor training intensity during soccer drills intended for physical development to allow the optimization of training parameters. Twenty-eight professional soccer players were assessed for heart rate ...

The aim of the present investigation was to compare the accuracy of the heart-rate (HR) deflection point (HRDP) and the second HR variability threshold (HRVTh2) to predict anaerobic threshold in boys. HRDP was determined from slope trends of successive linear regressions. HRVTh2 was determined from the high frequency's peak and ...

The aim of this study was to investigate the physiological load of free practices (F), qualifying sessions (Q), and official races (R) of motorcycling competitions. Twenty-six female riders (age: 30.8 +/- 6.1 yrs) participated in this study. Anthropometric and strength evaluations were performed. Subject's heart rate (HR) was continuously recorded ...

BACKGROUND/OBJECTIVE: The Actiheart (Mini Mitter, Sunriver, OR, USA) uses heart rate (HR) and activity data to predict activity energy expenditure (AEE). Currently, the Actiheart has only been tested during laboratory conditions. Therefore, the objective of this study was to validate the Actiheart prediction method against indirect calorimetry during a wide ...

Several methods are used to estimate anaerobic threshold (AT) during exercise. The aim of the present study was to compare AT obtained by a graphic visual method for the estimate of ventilatory and metabolic variables (gold standard), to a bi-segmental linear regression mathematical model of Hinkley's algorithm applied to heart ...

We examined potential mechanisms (autonomic function, hypotension, and cerebral hypoperfusion) responsible for orthostatic intolerance following prolonged exercise. Autonomic function and cerebral hemodynamics were monitored in seven athletes pre-, post- (<4 h), and 48 h following a mountain marathon [42.2 km; cumulative gain approximately 1,000 m; approximately 15 degrees C; completion ...

The purpose of the present study was to evaluate the reliability of the oxygen consumption/heart rate (VO(2)/HR) relationship used to estimate energy expenditure during a workday. Before and after a 6-10 h work shift, the VO(2)/HR relationship was measured in 57 workers (28 female, 29 male) in our laboratory. VO(2) ...

Heart rate (HR) and ratings of perceived exertion (RPE) are common exercise intensity regulatory strategies, however, some individuals are unable to use these strategies effectively. Alternative or conjunctive strategies may aid in the transition to self-guided programs. The purpose of the present study was to examine the value of a ...

The purpose of this study was to examine the effects of muscular power engagement, anaerobic participation, aerobic power level, and energy expenditure on postexercise parasympathetic reactivation. We compared the response of heart rate (HR) after repeated sprinting with that of exercise sessions of comparable net energy expenditure and anaerobic energy ...

AIM: Ratings of perceived exertion (RPE) have been shown similar across subjects of varying fitness when estimations are made at relative physiological criteria. Because few studies have investigated the influence of fitness during longer duration bouts, the current investigation compared overall exertion (RPE-O), leg exertion (RPE-L) and breathing/chest exertion (RPE-C) ...

We sought to determine if resetting of the carotid-vasomotor baroreflex function curve during exercise is modulated by changes in central blood volume (CBV). CBV was increased during exercise by altering: (1) subject posture (supine versus upright) and (2) pedal frequency (80 versus 60 revolutions min(-1) (r.p.m.)); while oxygen uptake ( ...

RATIONALE: The effects of chronic moderate alcohol consumption on cardiac function are not understood. Acute stress may affect cardiac function by shifting autonomic cardiac regulation in favor of the sympathetic nervous system. Although alcohol consumption often increases at times of stress, the interactive effects of stress and chronic moderate alcohol ...

Hypoperfusion of active skeletal muscle elicits a reflex pressor response termed the muscle metaboreflex. Dynamic exercise attenuates spontaneous baroreflex sensitivity (SBRS) in the control of heart rate (HR) during rapid, spontaneous changes in blood pressure (BP). Our objective was to determine whether muscle metaboreflex activation (MRA) further diminishes SBRS. Conscious ...

This study examined the strategy utilized by patients with cardiovascular disease to regulate exercise intensity using the Rating of Perceived Exertion (RPE) and tested if a step-up procedure would reduce overshoot of target heart rate (HR). Also the study investigated if Prescription Congruence and Intensity Discrimination, components of the Intensity ...

In order to determine whether there is any difference between voltage-gated calcium-channel antibody (VGCC-Ab)-positive and -negative groups in Lambert-Eaton myasthenic syndrome (LEMS), we compared the clinical and electrophysiological features between 13 patients with VGCC-Ab and 6 VGCC-Ab-negative patients. No obvious difference was observed in the various clinical features or findings ...

The purpose of this study was to determine the reliability and validity of regulating exercise intensity by ratings of perceived exertion in step dance sessions. Ten male college-aged students voluntarily participated in 2 step dance sessions for 45 minutes at 70-80% of their heart rate (HR) reserves with a 1-week ...

The cardiovascular consequences of hypoestrogenism in premenopausal women are unclear. Accordingly, the influence of menstrual status and endogenous estrogen (E(2)) exposure on blood pressure (BP), heart rate (HR), and calf blood flow in young (18-35 yr) regularly exercising premenopausal women with exercise-associated menstrual aberrations was investigated. Across consecutive menstrual cycles, ...

A major part of the ME consumed by ruminants (MEI) is dissipated as heat. This fraction, called heat production or energy expenditure (EE), is assayed largely by measuring O2 consumption (VO2). Conventional measurement of EE in controlled conditions in chambers does not reflect the complexity of natural, environmental, and social ...

PURPOSE: Circadian variation of the heart rate (HR) at the myocardial ischemic threshold was compared with that of the HR at the sympathetic tone threshold in 16 cases of effort angina pectoris. METHODS: The high (0.15-0.40 Hz, Hf) and low (0.03-0.15 Hz, Lf) frequency spectral components were extracted every twenty ...

Spontaneous baroreflex function and vascular changes were assessed in young adults during dynamical mild exercise. Windkessel time constant was assessed by two different methods: two-element windkessel model, and by an autoregressive (AR) model, while the baroreflex sensitivity (BRS, ms/mmHg) was assessed by the sequence method. Results showed a change in ...

The autonomic nervous system plays a critical role in regulating the cardiovascular responses to mental and physical stress. Recent neuroimaging studies have demonstrated that sympathetic outflow to the heart is modulated by the activity of the anterior cingulate cortex (ACC). However, the cortical modulation of cardiovagal activity is still unclear ...

BACKGROUND: Failure to reach 80% of maximal predicted heart rate (HR) during exercise may render a myocardial perfusion single photon emission computed tomography (SPECT) study non-diagnostic for ischemia detection. We sought to investigate the injection of atropine in patients who fail to achieve 80% of age-predicted HR during exercise performed ...

Social experiences, both positive and negative, may influence cardiovascular regulation. Prairie voles (Microtus ochrogaster) are socially monogamous rodents that form social bonds similar to those seen in primates, and this species may provide a useful model for investigating neural and social regulation of cardiac function. Cardiac regulation has not been ...

OBJECTIVE: This study examined the effects of in-task, moderate-intensity aerobic exercise on neuroelectric and behavioral indices of interference control, one component of executive control. METHODS: Forty-one participants completed a V O(2) max test to determine maximal heart rate (HR). On a separate day, event-related brain potentials and task performance were ...

Ventromedial prefrontal cortex (VMPFC) lesions can alter emotional and autonomic responses. In animals, VMPFC activation results in cardiovascular sympathetic inhibition. In humans, VMPFC modulates emotional processing and autonomic response to arousal (e.g. accompanying decision-making). The specific role of the left or right VMPFC in mediating somatic responses to non-arousing, daily-life ...

RATIONALE: Heart rate (HR) and oxygen consumption (VO(2)) are indicators of the intensity of exercise. Handrail support has been shown, during maximal treadmill testing, to blunt HR and VO(2) responses at a particular speed and grade, resulting in an increased treadmill time and overprediction in aerobic capacity. OBJECTIVES: This study ...

Different types of adaptation of the cardiovascular system to the gravitational forces (hypokinetic and hyperkinetic) have been described in the healthy and the sick subjects under resting conditions. The aim of the present study was to elucidate whether haemodynamic responses to the dynamic exercise performed under various gravitational conditions are ...

OBJECTIVE: This study aims to investigate the effect of transcutaneous electrical nerve stimulation, applied at bilateral acupuncture points PC6 (Acu-TENS), on recovery heart rate (HR) in healthy subjects after treadmill running exercise. DESIGN: A single blinded, randomized controlled trial. SETTING: Laboratory with healthy male subjects (n=28). INTERVENTIONS: Each subject participated ...

To compare upper airway mechanics, arterial blood gases, and tracheal contamination in horses with induced left laryngeal hemiplegia (recurrent laryngeal neuropathy [RLN]) treated by laryngoplasty/vocal cordectomy (LPVC) or modified partial arytenoidectomy (MPA). Repeated measures under the following conditions: Control, RLN, LPVC, and MPA. Six horses. Two trials were conducted under ...