Great progress has been made in sleep medical research in recent years and sleep medicine has thus evolved into a specialized medical field. Sleep apnea syndrome is one of the mostly commonly seen sleep disorders. It is now clear that sleep apnea has adverse effects on the heart and is a risk factor for several cardiovascular diseases. Studies have found that decreased heart rate variability (HRV) is a prognostic factor for cardiovascular disease and it also associated with higher mortality rate. Considering the confounding effect of BMI and sleep apnea severity, this work investigates the correlation between heart rate variability and AHI (apnea-hypopnea index which is used to characterize the severity of sleep apnea) by dividing patients into different BMI subgroups. This work includes 1068 male subjects with complete overnight ECG recordings. The low-frequency (LF), the high-frequency (HF) component and the LF/HF ratio of HRV are computed for the 10 BMI subgroups. The Bootstrap method and the BCa technique for confidence interval estimation are employed to verify the linear association between the HRV measures and the severity of sleep apnea. The experimental results show that statically significant correlation exist between LF/HF ratio and AHI for BMI ¡Ù28 patient groups. Statically significant correlation between LF and AHI also exists for BMI ¡Ù27 patient groups. These results demonstrate that the associations between some of the HRV measures and AHI are clearly BMI dependent.

No description available.

Problem: Mostly attributed to lack of time, only about 15% of Canadian adults are currently reaching the Canadian Physical Activity Guidelines (CPAG). Recently, studies have suggested that any bout of aerobic exercise reaching moderate to vigorous intensity has the potential to improve health. Methods: Sixty adults (20 young non-overweight adults, 20 overweight adults, 20 older adults) already doing some resistance training (RT) were recruited. Participants performed eight RT exercises during three visits. The objective was to identify the proportion of time spent at moderate to vigorous intensity during RT sessions. Results: Overall, the participants were at moderate to vigorous intensity during 82% of the time. However, the older adult group compared to the young adult group spent lower proportion of time at moderate to vigorous intensity during RT sessions. Conclusion: Most Canadian adults can reach HR equivalent to those achieved during moderate to vigorous aerobic activity by doing RT.

The purpose of the present study was to explore the relationship between internalized racism, stereotype threat, self-handicapping, test performance, and cardiovascular responses in Black individuals. Stereotype threat, or apprehension about confirming a negative stereotype, has been shown to lead to self-handicapping, poor academic performance, as well as increased cardiovascular reactivity. Internalized racism, or the acceptance of negative stereotypes about one's group, is a factor that may moderate these relationships. One-hundred nine (84% female, 16% male) Black undergraduates participated in a laboratory study. Half of the participants were put in a stereotype-threatened condition and the other half were in a neutral condition. The participants were permitted unlimited time in which to practice for a verbal test and then were tested on their verbal ability while their blood pressure was monitored. Results indicated that internalized racism moderates the relationship between stereotype threat and systolic blood pressure, but not diastolic blood pressure or heart rate. However, the moderating effect of internalized racism in the relationship between stereotype threat and self-handicapping or test performance was not significant. It seems that individuals who do not accept the negative stereotypes about Blacks as a group experienced increased systolic blood pressure responses in stereotype-threatened situations compared to Black individuals who do accept the negative stereotypes. The implication is that Black individuals who challenge negative stereotypes will feel more stress when placed in situations where they are at risk of confirming those negative stereotypes. This study provides insight into reasons for the variability of cardiovascular disease among Black Americans, who typically experience a higher incidence overall compared to other ethnic groups.

Animals can show different responses to fear for example by playing dead when there is no possibility to escape. This response is called tonic immobility (TI) and is a well-established test of fear to evaluate fearfulness. Long durations of TI are generally considered as high levels of fearfulness. Physiological changes observed during tonic immobility suggest that there are changes in the autonomic nervous system (ANS) strongly involved in this process. The main objective for this study was to analyse duration of tonic immobility and heart and ventilation rate during tonic immobility in three different species; domesticated High Andean chickens (Gallus gallus), wild-caught Ornate Tinamous (Nothoprocta ornata) and Chilean Tinamous born in captivity (Nothoprocta perdicaria). In this study needle electrodes were used to measure heart and ventilation rate. The time following induction of tonic immobility (i.e. after holding the bird on its back for 15 s) was characterized by a large increase in heart and ventilation rate. During tonic immobility a progressive decrease in heart and ventilation rate was observed in all species, significant in all cases except for heart rate between start and end of TI in chickens. The duration of TI was significantly longer in Ornate Tinamou compared to Chilean Tinamou and chickens. The same was observed in latency to first head movement. TI is probably controlled by the autonomic nervous system, but a heart rate variability analysis has to be done in order to determine the different relative contributions of the sympathetic and parasympathetic systems in these species.

Despite the large volume of research on tobacco withdrawal, the vast majority of studies have focused on the onset and remission of symptoms over the course of several days and weeks, with the earliest assessment periods occurring the day after cessation. To date, there has been no systematic study of the very early time course of the tobacco withdrawal syndrome, despite its obvious relevance to the maintenance of both smoking and postcessation abstinence. The published literature contains a range of estimates about the early appearance of withdrawal symptoms, but without reference to empirical data. The main objective of the current study was to conduct a comprehensive, multimodal assessment of the early time course of the symptoms associated with smoking withdrawal among cigarette smokers. Participants were 50 smokers randomly assigned to either abstain or smoke at their own pace during four hours in the laboratory. Dependent measures included a physiological measure (resting heart rate); sustained attention (the Rapid Visual Information Processing task; RVIP); selective attention to smoking stimuli (an emotional Stroop task); and self-report (the Wisconsin Smoking Withdrawal Scales; WSWS). After baseline assessment, participants were assigned to the two conditions and the dependent measures were collected every 30 minutes. Generalized Estimating Equations (GEEs) revealed that abstinent participants displayed greater withdrawal than continuing smokers on all measures with the exception of the Stroop task. Statistically significant differences in withdrawal were found within 60 minutes on heart rate, within 30 minutes on the RVIP, and between 30 minutes and 180 minutes postcessation on the various subscales of the WSWS. These findings provide the first evidence of the early time course of tobacco withdrawal symptoms, although further research is needed to distinguish withdrawal effects from drug offset effects. Implications for the understandi ng the maintenance of daily smoking and for the treatment of tobacco dependence are discussed.

Heart rate is tonically regulated by the two branches of the autonomic nervous system (ANS); parasympathetic activation decreases heart rate while sympathetic activation increases it. Previous studies on the ANS in chickens have focused mainly on embryonic development, but it is largely unknown what happens in the weeks following hatching. The present study focused on the development of the autonomic nervous system in 2 and 5 week old broiler and Red Junglefowl (RJF). Since broilers are less fearful, less stressed and less active than their wild ancestor RJF, a possible domestication effect on the sympathetic nervous system was investigated by evaluating both physiological and behavioural responses during stress. I found that the heart is mainly under control from the sympathetic nervous system in 2 and 5 week old broiler and RJF as propranolol significantly decreased heart rate during baseline and stress conditions while injection of atropine had little or no effect on baseline heart rates. When the adrenergic tone was blocked, heart rate still increased during stress, more so in 5 week old birds than in 2 week old birds. This suggests that some other physiological regulatory mechanism with fast recruitment is involved in the stress response and it matures in the weeks following hatch. No differences in behaviour between broiler and RJF were observed when the sympathetic nervous system was blocked. As both breeds show similar responses, a domestication effect on the ANS from these results cannot be confirmed.

Στην παρούσα διπλωματική εργασία παρουσιάζεται η μέθοδος της αναγνώρισης του μη γραμμικού δυναμικού συστήματος της καρδιαγγειακής ρύθμισης. Συγκεκριμένα, αυτή η μέθοδος εστιάζει στην αναγνώριση του Heart Rate Baroreflex μηχανισμού (ή αντίδραση πιεσοϋποδοχέα του καρδιακού παλμού) μέσω παρατηρήσεων της καρδιακής πίεσης η οποία αποτελεί την είσοδο και του καρδιακού παλμού ο οποίος αποτελεί την έξοδο του προς αναγνώριση συστήματος. Το μοντέλο αυτό βασίζεται στα έμφυτα χαρακτηριστικά του αυτόνομου νευρικού συστήματος, για την απεικόνιση των οποίων αναπτύσσουμε ένα προσαρμοζόμενο νεύρο-ασαφές σύστημα (ANFIS). Αυτή η μέθοδος μας επιτρέπει να ενσωματώσουμε τις φυσιολογικές λειτουργίες του νευρικού μας συστήματος όπως την συμπαθητική και παρασυμπαθητική, δια μέσου της επιλογής κατάλληλων συναρτήσεων συμμετοχής, οι οποίες αντικατοπτρίζουν επακριβώς, την συμπεριφορά των παραπάνω νεύρων για το προσαρμοζόμενο νεύρο-ασαφές σύστημα. Τα αποτελέσματα συμφωνούν με τα φυσικά χαρακτηριστικά του καρδιαγγειακού μηχανισμού ρύθμισης, όπως καθυστέρηση κατά την λειτουργία των παρασυμπαθητικών νευρών, διάρκεια κατά την λειτουργία των συμπαθητικών και διόρθωση ανάμεσα στο σήμα του καρδιακού παλμού και της καρδιακής ρύθμισης. Η σωστή εκτίμηση του Heart Rate Baroreflex μηχανισμού επιτρέπει στους κλινικούς γιατρούς να έχουν πιο αξιόπιστες πληροφορίες για τους ασθενείς τους. / This thesis presents the method of identification of nonlinear dynamic system of cardiovascular regulation. Specifically , this method focuses on the identification of the Heart Rate Baroreflex (or Baroreceptor Reflex ) mechanism by observation of the arterial blood pressure which is the input and heart rate which is the output of the system. This model is based on the inherent characteristics of the autonomic nervous system, so we develop an adaptive neuro- fuzzy inference system (ANFIS) to represent them. This method allows us to incorporate the physiological functions of our nervous system, such as sympathetic and parasympathetic nerves, through the selection of appropriate membership functions , which reflect accurately the behavior of these nerves for the adaptive neuro- fuzzy system . The results agree with the natural characteristics and physiological understanding of the cardiovascular regulatory system, such as delay in the parasympathetic function, durability in the function of sympathetic nerves and the correlation between the heart rate and the arterial blood pressure signals. Proper assessment of Heart Rate Baroreflex mechanism allows clinicians to have more reliable information for their patients.

The incidence of sudden death during or after squash play has become a source of concern. In order to screen for coronary artery disease, exercise stress testing has been advocated, by the American College of Sports Medicine (1986), for those at or above the age of 45 already exercising or before embarking on exercise. Eighteen veteran squash players (mean age 49 ± 3 yr) took part in the study. Heart rate response was monitored throughout a squash match and for an hour after play. ECG changes were monitored for one hour after squash play. Mean heart rate, throughout playing time was 148 ± 16 beats per minute (range 118 - 168 bpm), representing 86.7% of Predicted Maximum Heart Rate (PMHR). Mean maximal heart rate was 169 ± 14 bpm (range 141 - 186 bpm), representing 98.8% of PMHR. Thus squash represents a very high intensity activity for these players. On subsequent ECG monitoring, no abnormalities were detected. The results of this study confirm that squash is an extremely high intensity sport and that even veteran players play at a level close to their maximal. This level of play did not provoke subsequent cardiac arrhythmias in this small group of players, contrary to an earlier study that reported arrhythmias in one third of a group of younger players in the post match period. / Thesis (M.Med.Sc.)-University of Natal, 1997.

Previous research investigating endurance sports from a physiological perspectivehas mainly used constant or graded exercise protocols, although the nature ofsports like cross-country skiing and road cycling leads to continuous variations inworkload. Current knowledge is thus limited as regards physiological responses tovariations in exercise intensity. Therefore, the overall objective of the present thesiswas to investigate cardiovascular and metabolic responses to fluctuations inexercise intensity during exercise. The thesis is based on four studies (Studies I-IV);the first two studies use a variable intensity protocol with cardiorespiratory andblood measurements during cycling (Study I) and diagonal skiing (Study II). InStudy III one-legged exercise was used to investigate muscle blood flow duringvariable intensity exercise using PET scanning, and Study IV was performed toinvestigate the transition from high to low exercise intensity in diagonal skiing,with both physiological and biomechanical measurements. The current thesisdemonstrates that the reduction in blood lactate concentration after high-intensityworkloads is an important performance characteristic of prolonged variableintensity exercise while cycling and diagonal skiing (Studies I-II). Furthermore,during diagonal skiing, superior blood lactate recovery was associated with a highaerobic power (VO2max) (Study II). Respiratory variables such as VE/VO2, VE/VCO2and RER recovered independently of VO2max and did not reflect the blood lactate oracid base levels during variable intensity exercise during either cycling or diagonalskiing (Studies I-II). There was an upward drift in HR over time, but not inpulmonary VO2, with variable intensity exercise during both prolonged cyclingand diagonal skiing. As a result, the linear HR-VO2 relationship that wasestablished with a graded protocol was not present during variable intensityexercise (Studies I-II). In Study III, blood flow heterogeneity during one-leggedexercise increased when the exercise intensity decreased, but remained unchangedbetween the high intensity workloads. Furthermore, there was an excessiveincrease in muscular VO2 in the consecutive high-intensity workloads, mainlyexplained by increased O2 extraction, as O2 delivery and blood flow remainedunchanged. In diagonal skiing (Study IV) the arms had a lower O2 extraction thanthe legs, which could partly be explained by their longer contact phase along withmuch higher muscle activation. Furthermore, in Study IV, the O2 extraction in botharms and legs was at the upper limit during the high intensity workload with nofurther margin for increase. This could explain why no excessive increase inpulmonary VO2 occurred during diagonal skiing (Study II), as increased O2extraction is suggested to be the main reason for this excessive increase in VO2(Study III).