Objective The primary objective of this study was two-fold. First, to determine whether incidental physical activity (IPA), which is composed of both light-intensity physical activity (LPA) and sporadic moderate-intensity physical activity (MPA; physical activity accrued in bouts less than 10 minutes), was associated with cardiorespiratory fitness (CRF). Second, to determine whether sporadic MPA was associated with CRF. Methods Participants were abdominally obese (defined as a waist circumference > 102 cm in men and > 88 cm in women), inactive, adult men (N = 24; [mean ± SD] age = 55.5 ± 7.8 years) and women (N = 55; age = 52.3 ± 7.5 years) recruited from Kingston, Canada. Cardiorespiratory fitness was assessed using a graded treadmill test. IPA (activity ≥ 1 metabolic equivalent (MET)) and sporadic MPA (activity ≥ 3 METs accrued in bouts less than 10 minutes) was measured using the SenseWear Pro Armband (SWA). IPA and sporadic MPA were categorized into duration (minutes/day) and expenditure (MET-minutes/day). In secondary analyses, we investigated the association between LPA (activity between 1 – 2.99 METs), sedentary behaviour (SED; activity < 1.0 MET) and CRF. Results Participants accumulated an average of 326.6 ± 127 minutes of IPA per day which was composed of 40.7 ± 17.8 minutes of sporadic MPA and 285.9 ± 118.2 minutes of LPA. Both duration and expenditure of IPA were significantly associated with CRF independent of sex, however, after further control for body mass index and age neither association remained significant (p > 0.05). Sporadic MPA was significantly associated with CRF after control for covariates (p ≤ 0.05). Neither LPA nor SED were associated with CRF after control for covariates (p > 0.05). Conclusions IPA was not significantly associated with CRF, however, sporadic MPA was an independent predictor of CRF. / Thesis (Master, Kinesiology & Health Studies) -- Queen's University, 2011-07-30 16:43:47.703

No description available.

During dynamic exercise, the response of the cardiorespiratory system is structured to maintain homeostasis at the cellular level. The rate at which homeostasis is established is largely dependent on the system's structural and physiological integrity. Evidence suggests that any impairment in the functioning of the system might be reflected in a determination of oxygen uptake (VO[2]) kinetics. The kinetics of VO[2] have been quantified in response to step, impulse, ramp and sinusoidal changes in work rate (WR). An alternative approach uses a technique in which the WR is perturbed according to a pseudorandom binary signal. Pseudorandom binary sequence (PRBS) WR forcings have the advantage of being able to provide a determination of vo2 kinetics from a single test session of ~30 min duration. The assessment of VO[2]kinetics using PRBS WR forcings demands that the controlling process behaves in a linear manner. To minimise the contribution of non-linear influences, changes in work intensity must be constrained to the sub-lactate threshold domain. When examining clinical, untrained or young subjects, the necessary reduction in the upper work limit of a PRBS forcing can effect a fall in the distribution of power across the bandwidth of the sequence. If the distribution of power should fall below a critical level, then it can become difficult to elicit discernible responses from the forcing. To resolve this problem, this thesis investigated the potential for developing a multifrequent WR forcing altered to enhance identification of the underlying VO[2] response. The multifrequent WR forcing developed for use in this thesis took the form of a binary sequence. Binary transitions were determined according to a specially constructed multifrequent signal. Signal construction involved redistributing the available signal power to specific harmonics in a chosen range of frequencies. To validate estimates of VO[2] kinetics derived from the multifrequent binary sequence (MFBS) WR forcing, comparisons were made with the data obtained from an established PRBS forcing. When comparing physiological data, it is necessary to consider the amount of variability between trials. Therefore, prior to assessing the agreement between data obtained from the MFBS and PRBS methods, this thesis sought to establish the degree of variability in estimates of VO[2] kinetics derived from PRBS exercise tests. The results presented in this thesis show estimates of the mean response time (MRT) of VO[2] derived from the MFBS method to be 46.8 (4.2) s (mean (standard deviation) seconds), compared with 45.2 (5.0) s for the PRBS method. This suggests that the two methods yield comparable determinations of VO[2] kinetics. Supporting evidence is provided by the limits of agreement. These indicate that the maximum difference likely to occur between the MRT obtained from the two methods (-6.5 to +9.6 s) is less than that expected due to variability in the MRT derived from PRBS forcings (-11.6 to +8.0 s). However, the limits also reveal the poor repeatability of VO[2] response data obtained from the PRBS used in the thesis. Consequently, the use of this data to assess the validity of t the MRT derived from MFBS forcings is not recommended. In addition to poor repeatability, the possibility exists that assessments of VO[2] kinetics derived from MFBS WR forcings will also depend on the distribution of power across the harmonic content of the sequence. Therefore, whilst MFBS WR forcings may be suited to the assessment of VO[2] kinetics in subjects with a reduced tolerance to exercise, there remain doubts concerning both the validity of the response data and applicability of the method. Until these issues have been resolved, care would need to be taken when using estimates of VO[2] kinetics derived from MFBS WR forcings to determine the functional state of the cardiorespiratory system.

The increasing incidence of Alzheimer’s disease (AD) combined with recent evidence suggesting that its neuropathologies begin years prior to symptomatic onset has produced an immense focus on ways to attenuate the related structural and cognitive decline of certain brain regions. One low cost intervention is aerobic exercise. Rodent models have demonstrated aerobic exercise induces adult hippocampal neurogenesis, the birth of new neurons, in the dentate gyrus (DG) subregion of the hippocampus (HC) as well as increased performance on a spatial memory task. Further, human studies have demonstrated the association between increased cardiorespiratory fitness (CRF) and increased HC volume, and its translation to increased episodic memory performance. The goal of this study was to assess the relationship between CRF, as measured by VO2max, and brain region of interest (ROI) volumes notably including the left HC, left DG/Cornu Ammonis 3 (CA), and right entorhinal cortex (ErC). A secondary goal was to assess the relationship between CRF and cognitive performance on the Rey Auditory Verbal Learning Test. Baseline data was collected from 31 healthy older adults as a part of two larger clinical trials on aerobic exercise and HC function. Data included a CRF assessment as measured by VO2max, and structural MRI data including a high-resolution whole-brain T1-weighted image, and a T2-weighted image with higher-in-plane resolution. Automatic Segmentation of Hippocampal Subfields (ASHS) was the neuroimaging software utilized to segment the HC and medial temporal lobe cortices into its appropriate subfields. Multiple linear regressions ran in IBM SPSS 25 to determine if CRF predicted ROI volumes yielded no significant results when controlling for age, sex, intracranial volume, education, and scanner location. Multiple one-way between-subject ANOVAs conducted to compare ROI volumes in high-fit versus low-fit individuals revealed marginal significance for the left HC, but no other ROI. Multiple one-way between-subject ANOVAs conducted to compare cognitive performance in high-fit versus low-fit individuals also revealed no significant results. Considering the marginal significance achieved by the one-way between-subjects ANOVA for CRF and left HC, a larger sample size is needed to potentially achieve significant statistical significance. Given these remaining null results, further investigation is suggested using additional neuroimaging analyses that split the DG/CA3 into its anterior and posterior sections, as well as examining different aspects of the RAVLT or utilizing more sensitive episodic memory tests.

The aim of this research project was to conduct a manual development study and an open clinical trial in order to demonstrate the feasibility and efficacy of a mindfulness and acceptance based intervention for increasing cardiorespiratory fitness (CRF) in sedentary adults through adherence to a fitness walking program. Development of the treatment manual followed a 3-phase process (literature review and initial draft preparation, expert review, draft revision) based on expert systems analysis, and organizational structure was derived from Carroll and Nuro's Stage Model for Psychotherapy Manual Development. Field experts (N=3) were provided with the manual draft, as well as a semi-structured interview form for revision data. The manual included treatment introduction sections for the therapist and the participant, as well as 8 topic modules. In the10-week open trial, sedentary adults (N=24) engaged in a fitness walking program, while attending regular group therapy sessions whose content was based primarily on Acceptance and Commitment Therapy (ACT). Results indicated a large significant decrease in total walk test time [t(18) = 4.61, p = .0002, d = 0.64], with a mean decrease of 64.69 seconds. A moderate significant increase in estimated V0₂max [t(18) = -4.05, p = .0007, d = -0.43] was also evidenced, with a mean increase of 2.9 ml/kg/min. Analyses indicate a moderate non-significant increase in general experiential acceptance as measured by the AAQ-II [t(18) = 1.18, p = .26, d = 0.37], and a large significant increase in experiential acceptance of exercise-related internal experiences [t(18) = -9.19, p < .0001, d = -2.09] as measured by the PA-AAQ. Finally, feasibility and acceptability of the intervention were demonstrated through high levels of adherence to the walking program, group attendance, and measures of comprehension. This study demonstrated the usefulness of ACT in the field of behavioral medicine, particularly with health behavior change. / Ph. D.

No description available.

Aging is associated with adverse structural and functional changes in the brain. These changes have been directly linked to declines in certain types of learning and memory, likely due to the negative impact of aging on the hippocampus, a region necessary for cognitive functions such as relational learning, memory, and spatial navigation. Health behaviors and characteristics, like exercise and cardiorespiratory fitness (CRF), are related to better brain and cognitive aging, though more research is needed to better understand which age-sensitive aspects of cognitive function are most benefited by these health characteristics. The purpose of this collection of studies was to examine how exercise and fitness affect older adults’ learning and memory abilities, specifically using tasks that are designed to tax hippocampal binding processes. Further, I aimed to determine whether the volume of the hippocampus plays a key mediating role in this relationship. I answer these questions with three specific aims, each testing part of a model that represents complex interactions between physical activity, fitness, learning, and the potential mediator of hippocampal volume. The first aim examines these relationships using a cross-sectional design of 45 cognitively healthy older adults. The second aim evaluates the effects of a 12-week moderate intensity exercise program on 37 previously low-active older adults’ fitness, hippocampal volume, and relational learning rate. In this aim I first examine the amount of change in multiple variables following the intervention in order to infer causal relations, and then I examine the relationships of change across the different outcome measures. Finally, the third aim evaluates in 40 healthy older adults the role of hippocampal structure in the relationships between fitness and both spatial learning and memory in a virtual navigation task that has been found to be sensitive to age and disease-related changes in the hippocampus. In the first aim I found that higher cardiorespiratory fitness (CRF) was associated with larger hippocampal volume and faster relational learning rate. Larger hippocampal volume was also associated with faster learning rate. This pattern of results supports my hypotheses and provides a novel finding about how CRF relates specifically to older adults’ relational learning, which is thought to place demands on hippocampal binding. In the second aim I found that 12-weeks of regular light and moderate exercise increased CRF and early learning of relational associations. These changes were not larger for moderate intensity stationary cycling compared to light intensity stationary cycling. I also unexpectedly found that hippocampal volume decreased for both exercise groups, which suggests that this exercise intervention did not mitigate potential age-related decline in hippocampal volume. Finally, in the third aim I found that CRF was not related to learning object locations on spatial navigation, but higher CRF was related to fewer memory errors on the delayed recall of object locations in the virtual environment. Additionally, hippocampal volume was positively associated with the number of object locations learned after the first five minutes of free exploration in the virtual environment. Overall I found that higher CRF is related to faster relational learning and better memory of spatial object locations, both of which are expected to tax hippocampal binding processes. As even healthy older adults tend to experience structural and functional decline in the brain, CRF may be an effective health characteristic to target to increase the active life expectancy of our aging population.

Made available in DSpace on 2014-06-11T19:31:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-02-17Bitstream added on 2014-06-13T19:41:07Z : No. of bitstreams: 1 pereiraneto_gb_dr_jabo.pdf: 611965 bytes, checksum: cbfe3bec6677cdb3f5e2473f3db7b6cc (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A obesidade canina é uma das enfermidades nutricionais mais frequentemente observadas nos animais de companhia e pode provocar sérias influências sobre várias funções orgânicas, limitando a longevidade do animal. Neste estudo, avaliaram-se as possíveis alterações cardiorrespiratórias decorrentes da obesidade canina, assim como os efeitos da perda de peso corporal. Para tanto, utilizaram-se 11 cães obesos. Estes foram submetidos à restrição calórica de forma a perderem 20% do peso corporal e 11 cães com peso corporal ideal. Esses animais foram divididos em três grupos experimentais GI (cães obesos), GII (cães obesos após a perda de peso) e GIII (cães controle). Primeiramente, avaliaram-se a estrutura e função cardíaca mediante os exames ecodopplercardiográficos e mensurações da pressão arterial. Na segunda parte da pesquisa, os três grupos foram submetidos ao teste de estresse farmacológico com a infusão contínua de doses crescentes de dobutamina. Posteriormente, estudou-se a função respiratória por meio da hemogasometria e espirometria. Os resultados revelaram que os cães obesos apresentaram leve dilatação atrial esquerda, alteração das fases de despolarização atrial e ventricular e repolarização ventricular com a infusão de 32 μg/kg/min de dobutamina, maior resposta cronotrópica positiva frente a ação da dobutamina, menor pressão parcial arterial de oxigênio, além de volume corrente e frequência respiratória mais elevada em comparação aos cães com peso corporal ideal (GII e GIII). Desta forma, concluiu-se que a obesidade canina influencia principalmente os parâmetros respiratórios, não alterando a função sistólica e diastólica ventricular esquerda e a pressão arterial sistêmica, como também a correção da obesidade reverte as alterações encontradas nos cães obesos. / Canine obesity is one of the most frequently seen nutritional problems in pets and it can play an important role in organic functions and thereby restricts the animal longevity. This research evaluated the cardiorespiratory alterations of obese dogs and the effects of weight loss. For such, eleven healthy obese dogs underwent a caloric restriction weight-loss program, whose target weight was defined as 20% below their admittance body weight, as well as eleven ideal weight dogs. These animals were assigned into three experimental groups: GI (obese dogs), GII (obese dogs after weight loss) and GIII (ideal weight dogs). Firstly, the cardiac structure and function were assessed by echodopplercardiographic exam and arterial blood pressure mensurement. In the second part, the three groups were submitted to dobutamin stress testing. In either situation, the respiratory function was assessed by arterial blood gas analyses and spirometry. The results of obese dogs showed mild left atrial dilation, the influence of atrial and ventricular depolarization and ventricular repolarization alteration with 32 μg/kg/min of dobutamin, higher positive chronotropic response to dobutamin, lower oxygen arterial tension and tidal volume and higher respiratory rate than ideal weight dogs (GII and GIII). It was possible to conclude that canine obesity is detrimental mainly to respiratory parameters and do not change left ventricular systolic and diastolic function and systemic blood pressure, and weight loss can resume these abnormalities.

Adaptation to environmental fluctuations, through sensing and appropriate physiological responses, is crucial to homeostasis. Neuroepithelial cells (NECs) are putative chemoreceptors resembling mammalian Type I (glomus) cells. They have been shown to respond in vitro to changes in O2, CO2, NH3 and pH. Cytosolic carbonic anhydrase (Ca17a) is thought to be involved in CO2 sensing owing to its presence in NECs. A mutant line of zebrafish (Danio rerio) lacking functional Ca17a was generated using CRISPR/Cas9 technology and used to assess the role of Ca17a in initiating the cardiorespiratory responses to elevated CO2 (hypercapnia). Unfortunately, the homozygous knockout mutants (ca17a-/-) did not survive longer than ~12-14 days post fertilization (dpf), restricting experiments to early developmental stages (4-8 dpf). Changes in ventilation (fV) and cardiac (fH) frequency in response to hypercapnia (1% CO2) in wild type (ca17a+/+), heterozygous (ca17a+/-) and ca17a-/- fish were used to investigate Ca17a-dependent CO2 sensing and downstream signalling. Wild type fish exhibited hyperventilation during hypercapnia as indicated by an increase in fV. In the ca17a-/- fish, the hyperventilatory response was attenuated markedly, but only at 8 dpf. Hypercapnic tachycardia was observed for all genotypes and did not appear to be influenced by the absence of Ca17a. Interestingly, ca17a-/- fish exhibited a significantly reduced resting fH¬. This effect of knockout became more pronounced as the fish aged. Anesthesia did not contribute to the decreased fH in the ca17a-/- fish, nor did changes in cardiac adrenergic or cholinergic tone, which were probed using propranolol (-adrenergic receptor blocker) or atropine (muscarinic receptor blocker). The decrease in resting fH was prevented (“rescued”) when ca17a-/- embryos were injected with ca17a mRNA. Collectively, the results of this thesis support a role for Ca17a in promoting hyperventilation during hypercapnia in larval zebrafish and suggest a previously unrecognized role for Ca17a in determining resting heart rate.

No description available.