Abstract The purpose of this study was to examine thermal (body temperature, thermal sensation and comfort ratings), circulatory (blood pressure, heart rate variability) and neuromuscular performance responses to whole-body cryotherapy (WBC, -110 °C). Altogether 66 healthy subjects were exposed to WBC for two minutes. The acute and long-term changes were examined, when the subjects were exposed to WBC three times a week during three months. Skin temperatures decreased very rapidly during WBC, but remained such a high level that there was no risk for frostbites. The effects on rectal temperature were minimal. Repeated exposures to WBC were mostly well tolerated and comfortable and the subjects became habituated at an early stage of trials. WBC increased both systolic (24 mmHg) and diastolic (5 mmHg) blood pressures temporarily. Adaptation of blood pressure was not found during three months. The acute cooling-related increase in high-frequency power of RR-intervals indicated an increase in cardiac parasympathetic modulation, but after repeated WBC the increase was attenuated. The repeated WBC exposure-related increase in resting low frequency power of RR-intervals resembles the response observed related to exercise training. There are signs of neuromuscular adaptation, especially in dynamic performance. A single WBC decreased flight time in drop-jump exercise, but after repeated WBC these changes were almost vanished. This adaptation was confirmed by the change of the activity of the agonist muscle, which increased more and the change of the activity of antagonist muscle, which increased less/did not change after repeated WBC indicating reduced co-contraction and thus, neuromuscular adaptation.

The importance of physical exercise tends to be neglected in today’s modern lifestyle. This increased passive way of life conveys a notable increase in the prevalence of lifestyle disorders such as hypertension and vascular pathology which lead to cardiovascular strain. Taking this into account, the aim of this investigation was to explore the empirical association between the heart health status of an active and sedentary South African lifestyle, thus intending to provide insight into impact of the significant changes that are associated with the modernised society. With the aforementioned objective in mind, four separate studies were completed: Study 1 sought to investigate the cardiovascular status of 162 undergraduate university students in order to determine whether, despite their youth, students remained at risk of cardiovascular complications. Astonishingly, results indicate that a number of students between the ages of 18 and 25 in a university setting present with preeminent cardiovascular risk. This data highlights some serious concerns regarding the cardiovascular health among the youth. In sequel to study 1, study 2 permitted the comparison of a sedentary and active South African population, however some discrepancies originated due to the notable age difference between the groups. Nevertheless, results gained from this crosssectional comparison between the populations indicate significantly higher cardiac risk amongst the sedentary population. Study 3 was conducted on 202 infantry service recruits between the ages of 18 and 24 years. A pre- post intervention study design was incorporated in pursuit of determining the influence of an intense training programme on cardiovascular variables of a population over a 20 week time-frame. Results yielded from this study indicate a significant decrease in overall cardiovascular risk, as tested over three intervals (week 1, week 12, and week 20) during the 20 week training period. Study 4 was designed as a longitudinal study with self-controls for within group comparisons, as well as a comparative study between the two contrasting populations. Thus, affording the opportunity to determine the impact of physical activity on cardiovascular risk by comparing two divergent South African lifestyles over a 20-week time frame. The 202 infantry service recruits of study 3 served as the intervention group, while the control group comprised of 126 sedentary university students. Findings from this study conveyed strong association between the active population and decreased cardio-stress index and related heart health measurements in comparison to results of the sedentary population. This research validates the positive correlation between a physically active lifestyle and improved heart health, thereby implying reduced cardiovascular risk. In the combat against cardiovascular disease it is clear that focus should be shifted from pharmacological treatment to behavioural prevention. As a principle component of this preventative approach it is vital that individuals are equipped with screening technology that enables early detection and monitoring of probable cardiovascular complications. Several novel ideas were introduced in this research, including the endorsement of the cardio-stress index method as an efficient non-invasive technique to directly observe cardiovascular stress. / Dissertation (MSc)--University of Pretoria, 2014. / lk2014 / Physiology / MSc / Unrestricted

Human wellbeing, in a large component, relies on the harmony between the body and the mind. Unfortunately, we often miss or ignore important signals from our bodies, and sometimes this can negatively impact our health. Therefore, the use of intelligent systems that grasp such signals and convey them in an intuitive manner to our minds can result in great health benefits. In this Thesis, we introduce a family of multimedia technologies and techniques aimed at realizing such systems. We call them: Ubiquitous Biofeedback Multimedia Systems. Although the notion of clinical biofeedback has been around for years, we introduce the concept of Ubiquitous Biofeedback where the biofeedback operation is given geographical and temporal ubiquity attributes. A Ubiquitous Biofeedback reference model is introduced in the Thesis to provide an abstract structural representation of the various components at play in a typical non-clinical biofeedback environment. Two systems that implement the reference model’s components are presented. These systems implement the concept of Ubiquitous Biofeedback through the introduction of innovative stress management methods. An important component of these systems guides users through a relaxation routine. Therefore, a mathematical model is developed in the goal of personalizing the relaxation process. Its objective is to suggest relaxation techniques to a user during a stressful episode based on her or his preferences, history of what worked well and appropriateness for the context. The mental stress monitoring mechanism built into the Ubiquitous Biofeedback systems presented in this Thesis relies on the measurement of Heart Rate Variability (HRV). Therefore, HRV based methods for tracking mental stress accumulation and acute manifestations during long term monitoring have been devised. Also, since HRV signals can be plagued by artifacts, several algorithms are contributed to the effort of correcting such occurrences.

L'analyse de la Variabilité de la Fréquence Cardiaque est une méthode de mesure non invasive du Système Nerveux Autonome. Cette méthode d'analyse initialement utilisée dans le domaine clinique s'est progressivement installée dans le domaine de l'activité physique pour diverses applications telles que la détection précoce de la fatigue, le calibrage de l'intensité de l'entraînement, détecter les seuils ventilatoires... Les méthodes d'analyse peuvent être utilisées hors contexte de laboratoire, mais nécessitent néanmoins une attention particulière du point de vue méthodologique pour être cohérentes vis-à-vis des concepts mathématiques ou physiologiques qui les régissent. Chaque étape de cette méthode nécessite une rigueur spécifique pour ne pas conduire à une mauvaise interprétation. Ce document détaille le processus depuis la phase de mesure de l'intervalle RR en étudiant notamment la précision des appareils utilisables sur le terrain ou la correction du périodogramme obtenu en proposant différentes méthodes. Ce travail décrit également les indices de l'analyse de la VFC et les différentes limites techniques et conceptuelles. Les différents facteurs et biais influençant l'état du tonus du Système Nerveux Autonome seront décrits pour faciliter la création d'un protocole et l'analyse des indices de la VFC obtenus. / Heart Rate Variability Analysis is a non-invasive method for the evaluation of the Autonomic Nervous System activity. This analytical method initially used for clinical diagnosis progressively installed in the field of physical activity for various applications such as early detection of overreaching, calibration of training intensity, ventilatory threshold determination... These methods can be used outside the laboratory environment, but still require particular attention from a methodological aspect in order to be consistent with mathematical or physiological concepts underlying. Each step of this method requires a specific discipline not to lead to misinterpretation. This document details the process from the RR interval measurement phase including accuracy assessment of the devices used in the field or signal treatment with artifacts correction proposing several methods. This work details index from HRV analysis with their technical and conceptual limitations. External factors mat influence the Autonomic Nervous System are described to facilitate the protocol creation and results interpretation

O objetivo do presente estudo foi verificar a possibilidade de identificação dos dois limiares metabólicos pelo comportamento da VFC. Para isso, 22 voluntários do gênero masculino [74,5 + 7,99kg, 177,0 + 8cm, 23,86 + 1,69 (índice de massa corporal) e 9,10 % de gordura], habituados à prática do ciclismo, realizaram teste ergométrico em bicicleta estacionária com carga inicial de 120W e incrementos de 30W a cada 3min, até a exaustão. Durante todo o teste foram feitos os registros da freqüência cardíaca (FC) e de sua variabilidade (VFC) e ao final de cada carga foram coletados 25µL de sangue para análise da concentração sangüínea de lactato. Aplicou-se um modelo matemático que ajustou a curva da VFC em três retas e o primeiro e segundo limiar de VFC foram identificados nas intersecções entre as retas. Para identificação do primeiro e segundo limiar de lactato, considerou-se as concentrações fixas de 2,0 e 3,5mM, respectivamente. A análise de variância para medidas repetidas indicou não haver diferenças significativas nas cargas em que os limiares de VFC e de lactato foram encontrados, mostrando que a metodologia proposta pode ser promissora. Entretanto a falta de correlação entre as variáveis indica que novos estudos necessitam ser realizados para confirmação desta possibilidade. / The purpose of this study was to verify the possibility of metabolic thresholds identifications through HRV. For that, 22 male volunteers [74,5 + 7,99kg, 177,0 + 8cm, 23,86 + 1,69 (body mass index) e 9,10 % fat], familiarized to cyclism practice, realized a cycloergometer test with initial load of 120W and 30W increases every 3min., until exhaustion. During all test, it was registered heart rate (HR) and its variability (HRV) and, at the end of each load, it was collected 25mL blood for lactate concentration analysis. It was applied a mathematical model to adjust HRV curve in three straight lines and first and second HRV thresholds were identified in intersections among the lines. For the identification of first and second lactate thresholds, it was considered 2,0 and 3,5mM fixed concentrations, respectively. Variance analysis for repeated measures indicated that there were no significant differences between loads in which HRV and lactate thresholds were found, showing that purposed methodology can be promissor. However, the lack of correlation between variables indicate that new studies must be made to confirm that possibility.

Student musicians were recruited to participate in an experimental repeated measures research design study to identify effects of heart rate variability (HRV) biofeedback training and emotional self-regulation techniques, as recommended by HeartMath® Institute, on music performance anxiety (MPA) and music performance. Fourteen students were randomly assigned to a treatment or control group following a 5 minute unaccompanied baseline performance. Treatment group participants received 4-5 HRV training sessions of 30-50 minutes each. Training included bibliotherapy, using the computerized Freeze-Framer® 2.0 interactive training software, instruction in the Freeze-Frame® and Quick Coherence® techniques of emotional regulation, and also use of an emWave® portable heart rate variability training device for home training. Measures included the State-Trait Anxiety Inventory (STAI), Performance Anxiety Inventory (PAI), Flow State Scale (FSS), average heart rate (HR), and heart rate variability (HRV). Quade's rank transformed ANCOVA was used to evaluate treatment and no-treatment group comparisons. Combined MPA scores showed statistical significance at p=.05 level with large effect size of eta2=.320. Individual measurements of trait anxiety showed a small effect size of eta2=.001. State anxiety measurement showed statistical significance at the p=.10 level with a large effect size eta2=.291. FSS showed no statistical or effect size difference. PAI showed no statistical significance and a large effect size eta2=.149. HR showed no statistical significance and a large effect size eta2=.143. HRV showed statistical significance at p=.000 level and a large effect size eta2=.698. This study demonstrated practical/clinical significance of a relatively quick and inexpensive biofeedback training that had large effect at decreasing mental, emotional, and physiological symptoms of MPA for university students.

京都大学 / 0048 / 新制・課程博士 / 博士(社会健康医学) / 甲第22888号 / 社医博第112号 / 新制||社医||11(附属図書館) / 京都大学大学院医学研究科社会健康医学系専攻 / (主査)教授 川上 浩司, 教授 今中 雄一, 教授 稲垣 暢也 / 学位規則第4条第1項該当 / Doctor of Public Health / Kyoto University / DFAM

京都大学 / 新制・課程博士 / 博士(人間・環境学) / 甲第23272号 / 人博第987号 / 新制||人||233(附属図書館) / 2020||人博||987(吉田南総合図書館) / 京都大学大学院人間・環境学研究科共生人間学専攻 / (主査)教授 林 達也, 教授 船曳 康子, 教授 久代 恵介, 教授 森谷 敏夫 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DGAM

<p>Restricted and repetitive behavior (RRB) is a core feature of autism spectrum disorder (ASD). Research suggests that the severity of RRB may be influenced by both environmental variables (e.g., absence of sensory stimulation input) and neurophysiological activity within the body (e.g., atypical regulatory capacity of the autonomic nervous system). Substantial research efforts have been devoted to the assessment of factors that influence the occurrence of RRB in individuals with ASD, which have led to the development of assessment methodologies, such as functional analysis, to identify specific contexts in which RRB occurs, and measures of heart rate variability (HRV) to index the level of neurophysiological activity for individuals with ASD.</p><p>However, despite the increasing consensus that the assessment and treatment of RRB require a more comprehensive approach due to the complexity and heterogeneity of the neurodevelopmental disorder, there exists a paucity in research that addresses both the functional behavioral and neurophysiological dimensions of RRB. This study aimed to address this gap by (a) designing and evaluating the effects of an integrated function-based assessment on identification of the functional subtypes of RRB and (b) examining the relationship between RRB and HRV as an indicator of neurophysiological functioning. The study included six participants, ages four to seven, with ASD. A single-case alternating treatments design, with two conditions simulating low- and high-stimulation environments, was used for the assessment of functional subtypes within each participant. Dependent variables included the duration of RRB and HRV. RRB was measured using MOOSES, a multi-option observation system for experimental studies. HRV was measured using wearable technology that collects blood volume pulse. Visual analysis of time series data as well as nonparametric analyses of the dependent variables were conducted to determine the functional subtypes of RRB and the association between HRV and RRB across participants.</p><p>Study results suggest that (a) the integrated assessment is effective in identifying specific functional subtypes of RRB and (b) HRV is positively correlated with the rate of RRB. The findings of this study offer new insights on the understanding of how underlying environmental and neurophysiological mechanisms may influence the occurrence of RRB in ASD. Furthermore, the study provides an integrated assessment model that can be feasibly implemented in applied settings.</p>

This work is focused on fractal dimension utilization for heart rate variability analysis. Both the theory of heart rate variability and the methods of HRV analysis in time domain and using the fractal dimesion are summarized. Short comparsion of time domain and fractal dimension method is presented.