Purpose: Little is known about the heart rate (HR) responses at the onset of exercise, at peak exercise, and recovery in apparently healthy men and women. The purpose of this study was to determine the prevalence of abnormal HR acceleration at the onset of exercise, define the HR acceleration profile, determine if traditional cardiovascular disease (CVD) risk factors are associated with abnormal HR acceleration, and identify whether abnormal chronotropic responses cluster with abnormal HR acceleration in an asymptomatic, self-referred, adult population. Methods: A retrospective examination of a symptom-limited maximal treadmill test was performed for participants of a university-based fitness program between 1990 and 2006. Records were analyzed for various HR responses from individuals (N=947) of both sexes who represented a broad range of age and fitness levels (mean VO2: 32.9±9.4ml∙kg-1∙min-1). Abnormal HR acceleration at minute 1 and ⅓ total exercise time was defined as a HR increase from standing rest of ≤14 and ≤28 beats respectively. Results: The prevalence of abnormal HR acceleration at minute 1 and ⅓ total exercise time was 30.6% and 31.3% respectively. The mean HR increase during the first minute and ⅓ total exercise time was 20.5 ± 10.3 and 33.7 ± 10.4 beats respectively. Abnormal accelerators had a significantly better CVD risk factor profile (lower systolic and diastolic blood pressure, BMI, total cholesterol, triglycerides, higher VO2, and higher percent of regular exercise) than normal accelerators, despite consisting of a greater percentage of current smokers. Lastly, abnormal HR acceleration showed higher prevalence with abnormal HR recovery than with chronotropic incompetence. Conclusions: In the present study cohort, a lower HR increase at the onset of exercise was associated with a better CVD risk factor profile but the same differences were not seen at ⅓ total exercise time. / School of Physical Education, Sport, and Exercise Science

Positive psychology has led a movement that concentrates on positive characteristics. The current study examined the relationship between positive emotions, negative emotions, flourishing, languishing, and cardiovascular functioning. The study uses guided imagery to help participants recall a negative emotional event and positive emotional event in a counterbalanced order. The reverse order allowed us to examine the differential contributions of stress buffering versus facilitated recovery effects to higher levels of heart rate variability (HRV). The study also examined the relationship between mental health categories and known cardiovascular disease risk. Univariate analysis of variance revealed that positive emotions can serve as a stress buffer and dampen cardiovascular responses to a negative event. Also, analysis revealed a trend for the prediction that positive emotions can facilitate cardiovascular recovery following a negative event. Exploratory analysis did not reveal differences between a facilitated recovery group and a buffering group for cardiovascular measures. Future studies should include tighter control to help compare the differential influences of stress facilitation and stress buffering on cardiovascular functioning. The results from the study indicate that it is still too early to tell whether mental health buffers those individuals from developing CVD, and to answer whether languishing increases the risk of CVD. Longitudinal studies of young individuals without a prior history of any risk of CVD and who are flourishing or languishing might help provide answers to these questions.

published_or_final_version / Medicine / Master / Doctor of Medicine

Nine physiological measures were evaluated pre- to post-intervention on subjects participating in a university health promotion program over a seven-month period. Frequency of program attendance and choice of activity were also assessed. Of the 88 employees initially screened, most of the subjects were staff members (n=82, 93%),with a majority being female (n=68, 77%). Significant differences in physiological measures were found pre- to post-intervention between "higher" and "lower" cardiovascular risk participants, primarily due to the type of activity chosen. .The results indicate that health promotion programs at a university are an effective way to have an impact on employees in reducing their cardiovascular risk factors.

(Uncorrected OCR) Abstract Many studies have been conducted in Caucasian populations on the optimal body mass index cut-off for obesity, as well as the relationship between body mass index and percentage body fat and their associations with cardiovascular risk factors. However, few studies of this kind have been conducted in the Hong Kong Chinese population, This research is deemed to be important due to ethnic differences between Asians and Caucasians, Therefore, this dissertation aims to determine any ethnic differences from a sample of the local Hong Kong Chinese population, in order to advance health care policies controlling known cardiovascular risk factors. A total of 800 subjects were randomly selected from a pool of subjects participated in a Hong Kong Cardiovascular Risk Factor Prevalence study conducted in 1994-1996. These subjects were contacted and 453 disease-free subjects (210 males and 243 females) consented to participate in the current study, Data collected included serum and blood pressure measurements, body mass index, percentage body fat measured by bioelectrical impedance analysis, and a self-completed cardiovascular risk factor questionnaire, The mean age of the 453 subjects was 51.64 years (SD=12.3). When obesity was defined as percentage body fat ~ 25 and 2: 30 in males and females respectively, 23 kg/m2 was found to be the optimum cut-off value, with 78% correct classification (95% CI = 69%-87%). The corresponding sensitivity and specificity were 88% (95% CI = 81 %-95%) and 67% (95% CI = 57%-77%) respectively. On the other hand, if obesity was defined as percentage body fat ~ 25 and 2: 35 in males and females respectively, then 25 kg/m2 was found to be the best cut-off value with 82% correct classification (95% CI = 74%-90%). The corresponding sensitivity and specificity were 78% (95% CI = 69%-87%) and 85% (95% Cl = 78%-92%) respectively. Moreover, body mass index was found to be quadratically body fat. The quadratic relationship did not appear two genders, except that the percentage body fat of of females by 9.97 (SE=0.33). Finally, except for total cholesterol, high density lipoprotein cholesterol, and fasting glucose, body mass index did not provide any substantial information additional to percentage body fat on serum and blood pressure measurements. was the only measure on which percentage body fat did additional to body mass index. When waist-hip body mass index and percentage body fat,. except for body mass index did not have additional information on measurements when percentage body fat or/and [n conclusion, the optimal body mass index cut-off for obesity in Hong Kong Chinese was lower than the 30kg/m2 recommended by the World Health Organization, a clear reflection of ethnic difference between Asians and Caucasians. The quadratic relationship between percentage body fat and body mass index was similar in Hong Kong Chinese as in Caucasians and Blacks. Moreover, percentage body fat together with waist-hip-ratio were found to be better indicators of cardiovascular risk factors in Hong Kong. This was the first time such findings were found in the Hong Kong Chinese population. II / abstract / toc / Medical Sciences / Master / Master of Medical Sciences

This study evaluated a mandatory fitness assessment and counseling program designed to reduce coronary risk factors related to diet and exercise. The study was conducted at a southwestern graduate level theological institution. There were 19 mandatory and 22 voluntary participants. Each subject initially had either high blood pressure, high percentage body fat, or high total cholesterol. Significant changes were made within both groups regarding body fat percentage and diastolic blood pressure. Total cholesterol levels decreased for the voluntary group only. The mandatory group significantly improved their exercise level, yet still showed a significantly less positive attitude towards exercise. Overall, the fitness assessment and counseling was somewhat beneficial for both the mandatory and voluntary groups.

Bien que la lutte contre le tabagisme passif se soit récemment accentuée, la fumée de tabac demeure un des principaux polluants atmosphériques d’intérieur. Le tabagisme passif génère des réactions cardiovasculaires néfastes qui, lors d’expositions répétées, augmentent le risque de mortalité cardiovasculaire. Le but des travaux réalisés a été de repenser la toxicité cardiovasculaire aiguë de la pollution de l’air par la fumée de tabac, en analysant plus particulièrement le rôle joué par la nicotine sur les déterminants endothéliaux et sympathiques du tonus vasculaire.<p>Nous avons tout d’abord caractérisé, chez des volontaires sains non-fumeurs, les réactions vasculaires provoquées par une heure d’inhalation passive de fumée de tabac ou de fumée non tabagique.1 Nos résultats démontrent que le tabagisme passif provoque une réflexion plus précoce de l’onde de pouls au niveau aortique ainsi qu’une perte de la capacité vasodilatatrice microvasculaire dépendante de l’endothélium. De plus, nous avons observé que ces réactions sont spécifiques à la fumée de tabac, et perdurent plusieurs dizaines de minutes après l’arrêt de l’exposition. Le stimulus nicotinique exerce un rôle prédominant dans les changements de réflexion d’onde de pouls. Cependant, l’interprétation du rôle joué par la nicotine dans la toxicité endothéliale du tabagisme passif est limitée in vivo par les effets de la nicotine sur d’autres déterminants du tonus vasculaire, tel que le système orthosympathique. <p>Nous avons dès lors spécifiquement comparé, à l’aide d’un modèle d’aorte isolée de rats, les effets d’extraits de fumée de tabac, de fumée non tabagique et de nicotine pure sur la fonction endothéliale et la production radicalaire.2 Chaque type de fumée a entraîné une augmentation similaire de la production radicalaire au sein des vaisseaux, mais seul l’extrait tabagique a altéré la relaxation vasculaire dépendante de l’endothélium. Dans les mêmes conditions, la nicotine pure a respecté l’intégrité fonctionnelle de l’endothélium, ce qui permet d’exclure son implication dans les effets délétères aigus du tabagisme passif sur l’endothélium vasculaire. <p>Nous avons ensuite déterminé, par des mesures directes du trafic nerveux autonome sur une population de volontaires sains non fumeurs, les effets directs de la nicotine sur le contrôle chémoréflexe périphérique du système orthosympathique.3 Nos résultats démontrent que des taux de nicotine similaires à ceux générés par une heure d’exposition au tabagisme passif augmentent la sensibilité d’une importante boucle réflexe participant à l’homéostasie du système nerveux autonome. <p>Enfin, malgré tous ces effets délétères de la nicotine observés chez le non-fumeur, nous avons établi que la perfusion myocardique du patient à risque coronaire élevé n’est toutefois pas altérée par une prise de nicotine sublinguale.4 <p>Les effets cardiovasculaires du tabagisme passif sont rapides, spécifiques, et réunissent des conditions de stimulation orthosympathique et de dysfonction endothéliale potentiellement néfastes pour la perfusion coronaire. Les effets sympathicomimétiques de la nicotine représentent l’axe prédominant de la toxicité cardiovasculaire aiguë du tabagisme passif. Toutefois, la nicotine pure n’altèrant pas la perfusion myocardique du patient à risque coronaire, son utilisation peut donc être encouragée dans l’aide au sevrage tabagique. <p> / Doctorat en Sciences médicales / info:eu-repo/semantics/nonPublished