Browsing by Subject "Fitness"
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Item Beyond obesity : historical, social change approaches to improve the fitness of Americans(2014-08) Harrell, Baker Christian; Todd, JanAmerica's growing concern about fatness during the twentieth century developed in parallel with a society that made it increasingly harder to live a healthy lifestyle. Since the 1970s, sweeping political, economic, cultural, and familial changes have occurred in the United States. Many researchers argue that these changes have created an "obesogenic" environment that has contributed to the increased prevalence of overweight and obesity in America by favoring inactivity and the over consumption of highly-processed, calorie-dense foods and beverages. As a result, the field of public health has increasingly begun to recognize obesity as a "societal disease." In 2001, The Surgeon General's Call to Action to Prevent and Decrease Overweight and Obesity categorized the number of overweight and obese Americans as reaching "nationwide epidemic proportions." Since that time, America has waged an all-out "war on obesity." Instead of a broader emphasis on health promotion, some public health researchers have suggested that this heightened focus on obesity is 1) guided by America's historically-rooted social disdain for fatness and 2) insufficient to improve the healthy lifestyles of Americans. In searching for a solution to the so-called "obesity epidemic," a growing number of researchers have begun to look to models of social change. After an introductory chapter describing the scope of the problem, this dissertation provides an historical analysis of two, relevant social change models. The first historical case study is an examination of the Centers for Disease Control and Prevention's VERB social marketing campaign. The second study explores the model of social movements through the history of the aerobics "boom" of 1970s America. Based on these histories, this dissertation concludes by proposing a blended approach that harnesses the strengths of both models to organize and advance America's healthy living movement.Item Cerebrovascular reactivity and the fMRI-BOLD response in cardiorespiratory fitness(2015-08) Gonzales, Mitzi Michelle; Haley, Andreana P.; Tanaka, Hirofumi; Mumford, Jeanette A; Schnyer, David M; Maddox, W. ToddAccumulating evidence indicates that poorer vascular health accelerates cognitive decline and increases the likelihood of dementia in old age. Aerobic fitness, as a protective factor against vascular dysfunction, may thus serve to attenuate age-related cognitive pathology. The overarching aim of the current investigations was to determine the impact of cardiorespiratory fitness on cognition and its underlying neural substrates. Sedentary and endurance-trained middle-aged adults underwent general health assessment, neuropsychological testing, and functional magnetic resonance imaging (fMRI) during a working memory task and a hypercapnic (breath-hold) challenge. As compared with sedentary age-matched controls, the endurance-trained adults displayed a trend towards better executive function performance and faster reaction time on the working memory task, indicating enhanced speed of information processing. The neural substrates underlying fitness-related cognitive enhancement were explored by examining the blood oxygen level dependent (BOLD) response to a 2-Back working memory task. Additionally, breath-hold calibration of the working memory task was performed in order reduce vascular variance and provide a closer approximation of the neural contributions to the BOLD signal. After breath-hold calibration, the endurance-trained adults displayed greater working memory-related activation in the right middle frontal gyrus, indicating that fitness likely benefits the neural processes underlying cognition over and above global fitness-related changes in cerebrovascular reactivity. Finally, endothelial function was examined as a potential mechanism underlying fitness-related differences in cerebrovascular reactivity. Peripheral endothelial function failed to predict the BOLD signal to hypercapnia, suggesting that the response may be governed by nonendothelial-dependent vasoregulators. In summary, higher cardiorespiratory fitness at midlife may increase executive function abilities by enabling greater recruitment of neural resources during challenging cognitive tasks. Longitudinal studies will be instrumental in determining if these fitness-related changes are capable of modulating the trajectory of cognitive decline across the lifespan.Item Determination of the genetic basis of seed oil composition and melting point—adaptive quantitative traits—and their fitness effects in Arabidopsis thaliana(2013-12) Pelc, Sandra Elaine; Linder, C. RandalEvidence indicates seed oil melting point is likely an adaptive quantitative trait in many flowering plant species. An adaptive hypothesis suggests selection has changed the melting point of seed oils to covary with germination temperatures because of a trade-off between total energy stores and the rate of energy acquisition during germination under competition. The predicted differences in relative fitness under different temperatures have not yet been tested and little is known about the genetic basis of differences in oil composition. I used Arabidopsis thaliana to: (1) assess the fitness consequences of high and low melting point seeds germinating at different temperatures, (2) assess what genes underlie natural variation in seed oil composition, and (3) consider how these genes may be used to create oils with particular characteristics. To assess the effects of seed oil melting point on timing of seedling emergence and fitness, I competed high and low melting point lines of A. thaliana under cold and warm temperatures. Emergence timing between these lines was not significantly different at either temperature, which comported with warm temperature predictions but not cold temperature predictions. Under all conditions, plants competing against high melting point lines had lower fitness relative to those against low melting point lines, which matched expectations for undifferentiated emergence times. To assess the genetic basis of naturally occurring variation in seed oil melting point, the seed oil compositions of 391 accessions of A. thaliana were used in a genome-wide association study. Twelve genes were tightly linked with SNPs significantly associated with seed oil melting point variation. Seven encoded lipid synthesis enzymes or regulatory products. The remaining 5 encoded products with no clear relation to seed oil melting point. Results suggest selection can alter quantitative trait variation in response to local conditions through a small set of genes. 268 seed-expressed, candidate genes were linked to 103 SNPs associated with A. thaliana seed oil fatty acids. Eight genes were involved in lipid metabolism, and thirty-four encoded regulatory products. I discuss how knowledge of these genes can be used to breed and engineer desirable oil compositions for industry and nutrition.Item REPRODUCTIVE SUCCESS AND ANNUAL HABITAT PREFERENCE BY RED-SHOULDERED HAWKS IN SOUTHERN TEXAS(2011-05) Strobel, Bradley N.; Boal, Clint W.; Andersen, David E.; Haukos, David A.; Griffis-Kyle, Kerry; Blankenship, TerryIdentifying the vegetation characteristics resulting in habitat use by nesting raptors provides information important to species conservation and management. I examined nesting habitat preference of red-shouldered hawks (Buteo lineatus) using conditional logistic regression on characteristics measured at 27 occupied nest sites and 68 randomly selected unused sites in 2005–2009 in southern Texas. I measured vegetation characteristics of individual trees (nest trees and unused trees) and corresponding surrounding 0.04 ha plots. I evaluated the importance of tree and plot characteristics to nesting-habitat selection by comparing a priori tree-specific and plot-specific models using Akaike‘s Information Criterion corrected for small sample size (AICc). Models with only plot variables carried 14% more weight than models with only center-tree variables. The model-averaged odds ratios indicated red-shouldered hawks selected to nest in taller trees and in areas with higher average diameter at breast height (dbh) than randomly available within the forest stand. Relative to randomly selected areas, each 1-m increase in nest-tree height and 1-cm increase in the plot-average dbh increased the probability of selection by 85% and 10%, respectively. My results indicate characteristics of individual trees and the structure of the 0.04 ha area surrounding the tree, were associated with red-shouldered hawk nesting habitat selection. My results show red-shouldered hawks preferred taller nest trees (average 16.4 m) surrounded by larger diameter trees (average 25.4 cm) relative to the surrounding forest in southern Texas. Preference for taller nest trees by raptors is well documented and suggests an association with increased fitness. Further study is required to understand the mechanism responsible for this preference. Widespread alteration of forest communities combined with the well-documented preference for mature forests by breeding red-shouldered hawks (Buteo lineatus) has caused concern over the conservation of the species. Although habitat preferences of breeding red-shouldered hawks have been well documented, few data describe non-breeding-period habitat selection. I studied the seasonal habitat preferences of 12 adult red-shouldered hawks in southern Texas. I used radio-telemetry to collect >1,800 locations during 3 discrete phenological periods (winter, breeding-spring, and non-breeding-spring). I constructed phenological stage-specific discrete-choice models to compare the proportion of a 0.5-ha circle around each location (used and available) comprised of mature forests, young forests, brush, grass, wetland, and open-water cover types. I used general linear models to assess whether the amount of mature forest covertypes within used areas was dependent upon the sex of the individual, its breeding status, or the time of year the data were collected. During the breeding-spring-period, red-shouldered hawks preferred areas with greater amounts of mature forest cover types (selection ratio = 1.40, 95% CI = 1.16 - 1.69) and higher cover-type richness (selection ratio = 1.10, 95% CI = 1.04 - 1.21). Characteristics associated with habitat use during the breeding-spring-period were different than those associated with winter-period or non-breeding-spring-period habitat selection. Habitat use during the winter was associated with greener vegetation measured using the Normalized Difference Vegetation Index (NDVI), and avoidance of grasslands, brushlands, and wetlands. My data indicate the amount of forested cover types preferred by individual red-shouldered hawks depends upon the sex of the individual as well as its breeding stage (i.e., breeding, non-breeding). Habitat quality is often evaluated based on relative resource preferences, usually by examining disproportionate use of available resources. Alternatively, the Ideal Despotic Distribution hypothesis predicts that given a suite of territories to select from, an individual will select the highest quality territory in regards to its perceived fitness benefit. Presumably, the long-term occupancy rates of specific territories will be positively correlated with their quality. However, the predictions of the ideal despotic distribution hypothesis hinge upon the individual‘s ability to accurately assess territory quality (perfect knowledge), a condition that is difficult to meet under temporally and spatially variant environments. Using a 5-year data set on a resident population of red-shouldered hawks in southern Texas, I examined the predictions of the ideal despotic distribution hypothesis. My results were consistent with the prediction of the ideal despotic distribution hypothesis that the proportion of years a territory supported a nesting attempt was negatively related to the relative nest initiation dates. However, in contrast to the predictions of the ideal despotic distribution hypothesis, my data show that proportion of years a territory supported a nesting attempt was unrelated to the average number of eggs laid and negatively related to the average number of young fledged annually. Whereas the proportion of years a territory supported a nesting attempt varied across territories, the annual reproductive success of breeding red-shouldered hawks varied markedly from year to year and was positively associated with the number of breeding pairs observed. Overall, my results suggest that red-shouldered hawk reproductive success is influenced heavily by stochastic characteristics that violate the ideal despotic distribution hypothesis‘ assumption of perfect knowledge by individuals.