Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
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Item What Makes "Fun" Fun? Insights into Children's Participation in Physical Activity(2015) Hopple, Christine J.; Andrews, David; Graham, George; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A rapidly accumulating body of literature points to fun as an important factor in the physical activity participation choices of children. Few studies, however, have conducted systematic, in-depth investigations into what children mean when they say an activity is fun. Scanlan and Lewthwaite’s (1986) Sport Enjoyment Model was used to guide this inquiry into children’s enjoyment of physical activity in the contexts of Physical Education, organized youth, and recreation. This descriptive, mixed-methods study involved a convenience sample of 98 fourth through sixth graders from six classes in three non-traditional public schools in a mid-Atlantic state. Data collection methods included focus group and duo interviews, an activity-related drawing, and a quantitative measure including both Likert and open-ended questions. Qualitative data was inductively analyzed using comparative analysis techniques with triangulation occurring across all data sources. Findings suggest that the reasons children gave for enjoying and not enjoying physical activity were numerous, varied, and compelling in nature. Although many factors were perceived similarly by many children, others were perceived quite differently. Thus, there appears to be an idiomatic tendency of fun – that is, what each individual child will perceive to be either fun or not is particular to that specific child, with some factors being more salient than others. Contextual factors also strongly influence whether a child will find a specific physical activity to be fun or not, to the extent that these appear to have a stronger influence on the enjoyability of an activity than the activity itself. Lastly, data-gathering methods used with children (activity-oriented questions and card-sorting during focus group interviews) were very effective at stimulating discussion amongst children and uncovering what they think in a very non-threatening manner. Taken together, then, results suggest that the reasons as to why any given child will find an activity to be fun or not fun are complex, interwoven, highly individualistic, and dependent upon a number of contextual factors. Results can aid key players in developing policies and programs which hold the potential to increase children’s enjoyment in physical activity while concurrently decreasing their non-enjoyment of activity.Item Variability in Cognitive Performance and Learning in Younger and Older Adults Explained by Cardiovascular Fitness, Physical Activity, and APOE Genotype(2013) Kayes, Maureen K.; Hatfield, Bradley D; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation investigated the association of physical activity with cognition in two cross-sectional studies. Physical activity has been positively associated with cognitive function, and in older adult populations has shown an additional benefit for carriers of the ApoE- å4 allele. Cognitive training has also revealed a benefit for improved cognitive performance. Questions remain, however, about the interaction of these factors in their relation with cognition. One study addressed the relationship between physical activity and cognitive performance during executive function and working memory challenges in adults ages 50-70, and the other explored the role that physical activity plays in learning in adults ages 22-50 undergoing an online cognitive training intervention. In both studies, regard for influence of the ApoE genotype was considered, and the concept of specificity of physical activity was explored through employment of measures of both cardiovascular fitness and weekly physical activity kilocalorie expenditure. The study of older adults revealed that performance on a working-memory task was positively related to weekly kilocalorie expenditure in APOE-å4 carriers, with no such benefit for non-carriers during a moderate challenge condition of the task, while a positive relationship was revealed for both å4 carriers and non-carriers during a more challenging condition, but the magnitude of the relationship was greater in å4 carriers. The study of younger adults revealed no transfer benefits for cognitive training; however, cardiovascular fitness was positively related to performance after the intervention on a transfer task of proactive interference, and a positive trend was also found for cardiovascular fitness on a divided-attention language vocabulary learning task. No association was observed with regard to APOE-å4 genotype for any post-intervention task or learning transfer challenge. Taken together, these studies reveal that physical activity is associated with improved cognition in younger and older adults alike, but with specificity as to volume or intensity of physical activity mediating the relationship, cognitive processes benefited, and the role that the APOE-å4 genotype plays.Item Independent and joint effects of parental attitudes and special health care needs on physical activity and screen time among chlldren and adolescents in the United States(2012) Gingold, Janet Ann; Carter-Pokras, Olivia; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Sedentary lifestyles pose a threat to the health of children, especially those with special health care needs (SHCN). Using data from the 2007 National Survey of Children's Health, this study examined relationships between parental attitudes and low physical activity and high screen time among 6- to 17-year-olds with and without SHCN. Perceived limitation was associated with increased likelihood of low physical activity (AOR, 1.339; 95%CI, 1.079-1.662). Parenting stress (AOR, 1.189; 95%CI, 1.052-1.344) and lack of trust (AOR, 1.243; 95%CI, 1.104-1.399) were associated with increased likelihood of high screen time. Perceived limitation modified the effect of special health care needs status on high screen time. The likelihood of combined low physical activity and high screen time was greatest among children with SHCN whose parents reported both functional limitations in the child and parenting stress (AOR, 2.659; 95%CI, 1.741-4.060). Parental attitudes and SHCN should be addressed in interventions to promote active lifestyles.Item PARENTAL AND SCHOOL INFLUENCES ASSOCIATED WITH FIFTH GRADERS' HEALTHY EATING AND PHYSICAL ACTIVITY BEHAVIORS(2011) Michael, Shannon Lynn; Wentzel, Kathryn R.; Human Development; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Healthy eating and physical activity behaviors are decreasing among children in the United States. Despite growing evidence that parents and schools are important influences on the healthy development of children and adolescents, few studies have explored the relations between parental and school influences and children's positive health behaviors. This study, therefore, examined how the associations between parental and school health-related practices and children's healthy eating and physical activity behaviors differed according to varying levels of parental nurturance and school belongingness, and whether these associations were mediated by children's self-beliefs (i.e., physical appearance self-worth and physical self-efficacy). A parent, school, and combined model were tested. Based on data from the Healthy Passages study measured-variable path models were used to evaluate the direct, moderating, and indirect effects of parental and school influences on children's positive health behaviors for 5,147 fifth graders and their primary caregivers. Findings revealed that the three models for both healthy eating and physical activity had adequate model-data fit indices. Parenting practices, including regulating the watching of television and observing children being physically active, were related directly to children's healthy eating and physical activity, respectively. One moderating effect indicated that there was a positive association between eating meals together and children's healthy eating in homes with high and medium levels of father nurturance (see Darling & Steinberg, 1993). Both mother and father nurturance were indirectly related to children's healthy eating and physical activity via children's self-beliefs. In addition, children's physical self-efficacy partially mediated the relation between parents observing their children engage in physical activity and children's physical activity behaviors. One school practice, minutes per week of physical education, was predictive of children's physical activity. Children's self-beliefs fully mediated the relation between school belongingness and children's healthy eating and physical activity. The combined parent and school model provided a more complete explanation of children's positive health behaviors than did either of the singular parent and school models. The results of this study constitute an initial step toward evaluating exploratory causal models of children's healthy eating and physical activity behaviors. Implications of the findings and directions for future research are discussed.Item Circulating biomarkers of nitro-oxidative stress in young and older active and inactive men(2010) Bjork, Lori; Hagberg, James M; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Oxidative stress markers may be novel factors contributing to cardiovascular (CVD) risk. The purpose of this study was to examine the effects of long-term exercise, age, and their interaction on the plasma levels of the oxidative stress markers oxidized LDL (ox-LDL), nitrotyrosine, and myeloperoxidase (MPO), and to investigate whether these levels correlated with plasma NOx levels. Older (62 ± 2 yr) active (n=12) men who had exercised regularly for over 30 years and young (25 ± 4 yr) active (n=7) men who had exercised regularly for over 3 years were matched to older (n=11) and young (n=8) inactive males. Young subjects showed lower plasma nitrotyrosine levels than older subjects (P = 0.047). Young inactive subjects had higher ox-LDL levels than either the young active (P = 0.042) or the older active (P = 0.041) subjects. In addition, plasma oxidative stress levels, particularly ox-LDL, were correlated with various conventional CVD risk factors, and in older subjects were associated with Framingham risk score (r = 0.49, P = 0.015). The study found no relationships between plasma markers of oxidative stress and plasma NOx levels. The findings suggest that a sedentary lifestyle may be associated with higher ox-LDL levels and that the levels of oxidative stress markers may contribute to CVD risk.Item Investigating Neighborhood Walkability and its Association with Physical Activity Levels and Body Composition of a Sample of Maryland Adolescent Girls(2010) Jones, Lindsey Irene; Young, Deborah R; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Recent ecologic studies have begun to focus on characteristics of the built environment that influence physical activity (PA). Specifically, neighborhood walkability is emerging as an important determinant of PA in adults. At this point in time, there is conflicting evidence on how neighborhood walkability influences the PA levels of adolescents. The aim of this study was to investigate the relationship between individual's neighborhood walk score and individual's body mass index, body fat percentage, weight status, PA levels and meeting PA guidelines in a sample of adolescent girls. Additional analysis investigated the correlation between two objective measures of neighborhood walkability. This analysis was unable to show an association between PA levels or body composition of adolescent girls from the TAAG Maryland field site. Neighborhood walkability as assessed by the website walkscore.com was positively correlated with a GIS derived walkability index (r=.63 p<.0001).Item Exercise and Depression: Causal Sequence Using Cross-Lagged Panel Correlation Analysis(2009) Scott, Virginia Anne; Andrews, David L; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This study sought to determine what kind of causal relationship, if any, exists between exercise and depression. A university student population (N = 178) was given the Godin Leisure Time Exercise Questionnaire and the Beck Depression Inventory-II at two time points separated by approximately one month. Cross-lagged panel correlation was used to make causal inferences based on the strength of the temporal relationships. After meeting the assumptions of synchronicity and stationarity, there was no significant difference between the cross-lagged correlations (ZPF = -0.4599, p = 0.65). Thus, no single causal pathway was dominant. While equal cross-lagged correlations can indicate spuriousness, it can also signify reciprocal causation. Exercise was not clearly the cause of reductions in depression, but neither was depression clearly the cause of physical inactivity. More complex causal pathways, such as reciprocal causation, warrant further investigation.Item The Effects of Low-Fat Diet and Exercise on C-Reactive Protein and Metabolic Syndrome: Findings from a Randomized Controlled Trial(2008-07-09) Camhi, Sarah Michelle; Young, Deborah R; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Background: Low-fat diet (D) and exercise (E) are recommended for reducing cardiovascular disease risk. However, the independent and combined effects of D and E on C-reactive protein (CRP) and metabolic syndrome (MS) are unknown. Purpose: The purpose of this dissertation was to examine the changes in CRP and MS between control (C), D, E and diet plus exercise (D+E). Methods: Men (n=197) and postmenopausal women (n=180) with elevated low-density lipoprotein cholesterol and reduced high-density lipoprotein cholesterol, were randomized into a one-year trial with four groups: C, D, E or D+E (Stefanick et al., 1998). Weight loss was not an intervention focus. This secondary data analysis evaluated stored plasma samples for high-sensitivity CRP. MS prevalence was retrospectively found using the NCEP-ATP III definition. CRP change (ΔCRP) was examined between intervention groups using ANCOVA. Differences between groups for MS at follow-up were retrospectively investigated using logistic regression. All analyses were stratified by gender and controlled for baseline values, body fat change and other appropriate covariates. Results: In women, ΔCRP was different between D+E vs. C (-0.7 ± 0.33 mg/L, p = 0.04) and D+E vs. E (-0.9 ± 0.32 mg/L, p = 0.004). Women also had a decrease in CRP within D+E (Δ log CRP 0.2 ± 0.035 mg/L; p = 0.0002). After the intervention, ΔCRP did not differ for men between or within treatment groups. MS at follow-up was not different between C, D, E or D+E in either men or women. In women with MS, ΔCRP was different between D+E vs. C (-1.3 ± 0.43 mg/L; p = 0.006), D+E vs. E (-1.1 ± 0.44 mg/L; p = 0.02), and D vs. C (-1.2 ± 0.43 mg/L; p = 0.009). In women with MS, CRP decreased from baseline within D+E (Δ log CRP 0.2 ± 0.039 mg/L; p=0.0008). At follow-up, there were no differences between or within groups for ΔCRP in men with MS, or men without MS and women without MS. Conclusion: D and D+E may be effective treatments for reducing CRP in women with MS. Further studies are needed to replicate results and clarify the influence of gender.Item Effect of long-term exercise on endothelial progenitor cells in healthy humans(2008-04-24) Witkowski, Sarah; Hagberg, James M; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Endothelial progenitor cells (EPCs) are derived from the bone marrow and have been found to play a role in postnatal neovascularization and re-endothelialization. Reduced EPC number and function have been associated with death from cardiovascular diseases, CVD risk factors, and endothelial dysfunction. Oxidative stress, specifically, oxidized LDL (OxLDL) has been shown to decrease EPC number and function, and increase EPC senescence in vitro. Regular physical activity is related to lower rates of CVD; however the mechanisms underlying the benefits of exercise in the prevention of CVD are not fully clear. Exercise may improve the number, and function of EPCs while improving oxidative stress status. The primary purpose of this study was to compare CD34+/KDR+ EPC number, EPC clonogenic capacity, and senescence, in healthy men that have participated in greater than 20 years of moderate- to high-intensity exercise with low-active control subjects. To assess the effect of physical inactivity on these markers, a subset of exercisers (n=10) stopped exercising for 10 days after which, measures of EPC number, colony forming units, and senescence, endothelial function and oxidative stress were re-evaluated. Results showed that, CD34+/KDR+ cell number, CFU-Hill colonies, and EPC senescence were not statistically different between athlete and control groups. CD34+/KDR+ cell number was closely related to endothelial function. Specifically, the forearm blood flow response to reactive hyperemia was correlated with CD34+/KDR+ number in sedentary participants. Additionally, 5 athletes significantly decreased their CD34+/KDR+ number, which was related to a significant decline in endothelial function, indicating that regular physical activity is important for some athletes to maintain healthy endothelial function, perhaps through the maintenance of elevated number of circulating CD34+/KDR+ cells. CFU-Hill colony number was strongly correlated with hyperemic blood flow response in control participants and related to oxLDL independent of physical activity status. Athletes who participated in 10-days of exercise detraining demonstrated a significant decrease in EPC senescence, which was related to improved total antioxidant capacity. Overall, these results show that CD34+/KDR+ number is closely related to endothelial function. Moreover, the function of EPCs appears to be affected by oxidative stress and antioxidant availability.Item Differences in Perceived Stress, Affect, Anxiety, and Coping Ability Among College Students in Physical Education Courses(2007-04-25) Levine, Rachel Permuth; Gold, Robert S; Public and Community Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Because college students are a unique group with distinct environmental, situational, and interpersonal stressors, they are an important population for studying potential stress management techniques. Since physical activity is a renowned means of stress reduction, a logical area for exploration is whether college students' engagement in various forms of physical activity courses is related to improvements in individual perceptions of health-related constructs from the start of a course until its end. The purpose of this research was to understand whether college students who were enrolled in various physical education courses differentially self-report perceived stress, anxiety, coping ability, and affect after the conclusion of their courses. Specifically, this study examined whether these differences existed between students enrolled in yoga classes and those who were enrolled in other Kinesiology courses such as weight lifting, aerobics, and golf. This cross-sectional exploratory study involved a self-administered questionnaire that was administered at the end of Summer 2006 semester. 108 students met inclusion criteria. Survey sections addressed each of the independent and dependent variablesidentified for the study and included the following reliable and valid survey instruments: Perceived Stress Scale, Brief COPE, Inventory of College Students Recent Life Experiences, Positive and Negative Affect Scales and State Trait Anxiety Inventory. The final section of the survey collected student characteristic and attitudinal information. Contrary to the main hypothesis that students enrolled in yoga classes would report less perceived stress, they actually reported significantly more perceived stress than their counterparts (p <. 002). However, yoga students reported using more positive coping strategies over the past month than nonpractitioners (p <.008). More research needs to be conducted with pre-and post-tests between students or other population groups who practice yoga in order to understand whether yoga practice may be a factor in reducing stress over time. The observations from this study suggest that yoga may be a unique type of physical activity that may be 'sought out' by high-stressed persons or those wishing to learn strategies to cope with their stress.