School of Public Health

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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.

Note: Prior to July 1, 2007, the School of Public Health was named the College of Health & Human Performance.

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End date: 2009Subject: search.filters.subject.Health Sciences, General

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Now showing 1 - 10 of 20
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    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.
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    MULTI-DIGIT HUMAN PREHENSION
    (2009) Park, Jaebum; Shim, Jae Kun; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The current dissertation addresses the central nervous system (CNS) strategies to solve kinetic redundancy in multi-digit static prehension under different geometries of hand-held objects and systematically varied mechanical constraints such as translation and rotation of the hand-held object. A series of experiments conducted for this dissertation tested the following hypotheses suggested in the current literatures for multi-digit human static prehension: Hierarchical organization hypothesis, principle of superposition hypothesis, proximity hypothesis, and mechanical advantage hypothesis. (1) Forces and moments produced by fingers during circular object prehension were grouped into two independent subsets: one subset related to grasping stability control and the other associated with rotational equilibrium control. This result supports the principle of superposition hypothesis. Individual fingers acted synergistically to compensate each other's errors. This result confirms the hierarchical organization hypothesis in circular object prehension. (2) During fixed object prehension of a rectangular object, the closer the non-task fingers positioned to the task finger, the greater the forces produced by the non-task fingers. However, during free object prehension, the non-task fingers with longer moment arms produced greater forces. The former and latter results support the proximity hypothesis and the mechanical advantage hypothesis, respectively. (3) The grasping stability control and rotational equilibrium control were decoupled during fixed object prehension as well as free object prehension. This result supports the principle of superposition hypothesis regardless of the mechanical constraints provided for these two prehension types. (4) During torque production, the fingers with longer moment arms produced greater forces when the fingers acted as agonists for the torque production. Therefore, the mechanical advantage hypothesis was supported for agonist fingers. (5) Coupling of thumb normal force and virtual finger normal force was not necessitated when horizontal translation of hand-held object was mechanically fixed. However, the coupling of two normal forces was always observed regardless of given translational constraints, and these two normal forces were independent to other mechanical variables such as tangential forces and moments. This result supports the principle of superposition hypothesis in static prehension under varied combinations of translational constraints.
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    Global Capitalism Meets Local Postcommunism: Tensions in Transition as Manifested through Physical Culture and the Female Body in Romania
    (2008-11-21) Chin, Jessica; Andrews, David L.; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Nearly two decades after communism officially ended in Romania, the nation continues to struggle in its transition from state socialism to liberal democracy. The increased presence and influence of Western images, democratic ideals, and social ideologies produces a complex and unstable tension with persisting legacies of communism and socialist ideologies. This dissertation is a critical analysis of the ways in which various tensions are manifested within the changing physical culture in Romania, particularly through performative bodies and constructed spaces of leisure and physical activity. In addition, participation in sports and other physical activities related to fitness and health are examined to reveal disciplinary techniques that reinforce normalized constructions of gendered and classed bodies. Using a qualitative, multi-method approach, empirical data was primarily collected in gyms and fitness clubs of three major cities in Romania. Through a contextual, interpretive, and theoretically-informed analysis of the empirical findings, this project intends to expand upon and articulate theories of postcommunist transition, gender, and physical culture in the Eastern European context--opening new lines of inquiry that consider both the empowering and problematic implications of creating and negotiating new subject positions within postcommunist environments.
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    The influence of visfatin and visfatin gene polymorphisms on glucose and obesity-related variables and their responses to aerobic exercise training
    (2008-08-12) McKenzie, Jennifer A; Hagberg, James M; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Adipokines, soluble factors produced by adipocytes, may help to connect diabetes and obesity; one such adipokine is visfatin. Previous research has linked visfatin and visfatin gene (PBEF1) polymorphisms with glucose and obesity-related conditions; however, less is known regarding visfatin's response to an aerobic exercise training intervention, and no one, to our knowledge, has examined whether polymorphic variation in the PBEF1 gene affects aerobic exercise training-induced changes in glucose and obesity-related variables. Thus, this retrospective study investigated whether 6 months of aerobic exercise training reduced plasma visfatin levels in individuals with impaired glucose tolerance (IGT) or normal glucose tolerance (NGT). In addition, we examined the influence of common PBEF1 gene polymorphisms (-4689 G>T, -1543 C>T, -1001 T>G, -948 G>T, and SER301SER) and haplotypes on glucose and obesity-related variables and their responses to aerobic exercise training. Following the completion of 6 weeks of dietary stabilization, 116 healthy, sedentary, middle-aged, Caucasian men and women underwent 6 months of aerobic exercise training. Glucose total area under the curve (AUC), insulin AUC, and insulin sensitivity were measured via oral glucose tolerance tests. Plasma visfatin was measured using an enzyme immunoassay in 67 of the participants (22 with IGT, 45 with NGT), and standard techniques were used to assess lipoprotein-lipid and body composition variables. Restriction fragment length polymorphism techniques and TaqMan assays were used to determine PBEF1 genotypes. We found that plasma visfatin levels were comparable in IGT and NGT individuals at baseline and increased similarly in both groups in response to aerobic exercise training. We also found associations at baseline between glucose and obesity-related variables and PBEF1 gene variants, with -4689, -1001, -948, and SER301SER variant allele groups and PBEF1 variant allele-containing haplotypes having higher insulin sensitivity. Last, PBEF1 genetic variation influenced the aerobic exercise training-induced change in glucose and obesity-related variables. Moreover, the -948 polymorphism, TCGTT haplotype, and TCGGT haplotype were associated with lipoprotein-lipid changes with training, and the SER301SER polymorphism influenced changes in BMI and body fat. Future studies need to address the functional significance of PBEF1 polymorphisms and haplotypes and clarify mechanisms connecting visfatin to glucose and obesity-related phenotypes.
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    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.
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    TNF Promoter Polymorphisms Associated with Skeletal Muscle Phenotypes in Humans
    (2008-01-24) Liu, Dongmei; Roth, Stephen; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Skeletal muscle plays a central role in the overall health of individuals across all ages, and skeletal muscle phenotypes are influenced by both genetic and environmental factors. Tumor necrosis factor alpha (TNF-α), a key player in the innate and adaptive immune responses, has long been recognized as a potent catabolic factor mediating muscle wasting in various pathological conditions. Overproduction of TNF-α has been implicated in the etiology of age-associated muscle loss (sarcopenia). Individual capacities to produce TNF-α vary widely, which is partially attributable to gene sequence variations. The TNF-α coding gene, TNF, is highly polymorphic and single nucleotide polymorphisms (SNPs) in the promoter region of TNF have been implicated for the transcriptional regulation of TNF-α production, and associated with numerous inflammatory and infectious diseases. The purpose of the present study was to investigate the association of muscle phenotypes, including sarcopenia, with 5 TNF promoter SNPs, which are potentially of biological significance. A total of 1050 volunteers participating in the Baltimore Longitudinal Study of Aging (352 and 407 white women and men, 127 and 107 black women and men, and 30 and 27 non-white and non-black women and men) were genotyped for 5 TNF SNPs, and their regional and total body soft tissue masses and muscle strengths of upper and lower limbs were measured. Results indicated that TNF promoter SNPs are associated with muscle phenotypes in the participants: putative high TNF-α-producing alleles at positions -1031 and -863, individually or in combination in haplotype '1031C-863A-857C-308G-238G', are associated with lower muscle mass in males. These results suggest that genetic variation in the TNF locus may contribute to the inter-individual variation in muscle phenotypes, and imply that TNF-α may have a potential role in regulating body composition even in healthy people.
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    On the Development of Postural Stability During Infancy as a Process of Growth and Active, Exploratory Sensorimotor Tuning
    (2007-12-04) Metcalfe, Jason Scott; Clark, Jane E; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The process by which humans stabilize bipedal stance represents a confluence of changes associated with musculoskeletal maturation and experience-based sensorimotor learning. While investigations have documented a variety of changes with increased bipedal experience, such as reduced velocity and frequency of postural sway and concomitant refinements in muscle activation sequences, the extent to which these changes may be ascribed to growth versus learning processes has not been well characterized. For example, reduced sway frequency is a natural consequence of increasing body height but alternatively, may be explained by active modulations in motor commands specifying the timing and magnitude of muscular activation sequences. It is clear that both types of influences are needed to explain postural development. However, a parsimonious framework for understanding and explaining postural development has yet to be clearly articulated and validated against empirical observations. As such, the purpose of this dissertation was to initiate the development of such an account through a combination of empirical and computational studies. In this dissertation, data are presented from a longitudinal study of upright posture in infants ranging from the onset of independent sitting until 9 months of walking experience; this dissertation focused on the particular period spanning from walk onset onward. Infants participated in a quiet stance task involving hand contact with a surface that was either static or dynamic as well as an independent stance condition. Empirical analyses were performed to estimate the statistical properties of sway and characterize adaptations to static and dynamic manipulations utilizing the touch surface. An unexpected lack of significance for sway magnitude was observed in all conditions. Robust effects, however, were found across measures of rate properties of sway. Taken in the context of previous literature, the empirical observations were used to guide a final study utilizing computational techniques to test hypotheses regarding potential sources of change in postural development. First, the mechanical and computational requirements for postural stabilization were systematically assessed through a review of extant models of both stance and motor learning. Armed with insights from this review, the final study examined an autonomous reinforcement learning algorithm, that was designed to capture the essence of how a human may stabilize his or her posture under the tutelage of exploratory action. Simulation results provided evidence in support of conclusions regarding changes in rate-properties of postural sway and underlying associations with physical growth as well as calibration of both sensory and motor system parameters. Further, simulations emphasized the importance of inclusion of noise in biologically-relevant aspects of the model, such as in sensory and motor processes, as well as the need to consider physical morphology as a primary constraint on sensorimotor learning in the context of upright postural development.
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    The Relationship Between Physical Activity and Executive Control Functioning as Modified by Genotype
    (2007-08-03) Hearn, Joe W.; Hatfield, Bradley D.; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    As we age, the structure of the brain deteriorates and cognitive functioning declines. The region of the brain that begins to age the fastest is the frontal lobe, in which the dorsal-lateral prefrontal cortex is involved in executive control functions such as planning, organizing, initiating behaviors, and working memory. For some individuals, the brain declines more rapidly with age because of genetic factors. Apolipoprotein E (APOE) is a gene that assists in the transport of cholesterol and repair of the brain when it is damaged. Presence of the ε4 allele impairs cholesterol transport and puts its carriers at risk for increased cognitive decline and possibly dementia of the Alzheimer's type (DAT). Physical activity can slow the aging process of the brain and delay the onset and severity of cognitive decline and DAT as it increases oxygenation and blood flow, neuronal growth and synaptogenesis, and it increases the expression of genes helpful to the functioning of the brain such as brain-derived neurotrophic factor (BDNF). Therefore, individuals at greater genetic risk for age-related cognitive decline (i.e., ε4 carriers) should receive increased benefit from physical activity. Accordingly, this study examined the relationship between physical activity and executive control functioning, assessed by the Wisconsin Card Sort Test (WCST) in middle-aged APOE ε4 carriers and non-carriers. High-active participants were predicted to perform better than their low-active counterparts, and this difference should be even greater among APOE ε4 carriers. While most research studies on this topic have focused on general cognitive performance, the present study is specific in its focus on executive control functioning. Sixty-seven cognitively normal middle-aged adults between the ages of 50 - 70 years were assessed on medical history, overall cognitive functioning, APOE genotype, level of physical activity, and executive control functioning (WCST). Using hierarchical regression, seven WCST variables were regressed on age, genotype, physical activity, and the interaction between genotype and physical activity. Analysis revealed that as level of physical activity increased, performance significantly improved on all seven WCST variables for APOE ε4 carriers, but not for non-carriers. These results reveal that the benefits of physical activity to cognitive performance in this age group are specific to those who are genetically at-risk for cognitive decline.
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    Association Between ACE Genotype and Skeletal Muscle Strength and Volume, and Their Response to Strength Training in Older Adults
    (2007-06-29) Charbonneau, David; Roth, Stephen; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Introduction: Previous studies have linked an insertion/deletion polymorphism in the angiotensin-converting enzyme (ACE) gene with variability in the response of muscle strength and mass to strength training, though conclusions have been inconsistent across investigations. The purpose of this study was to investigate the possible association between ACE genotype and skeletal muscle strength and volume, and their adaptation to strength training. Methods: A group of older, sedentary adults completed 10-weeks of strength training. Quadriceps muscle strength and volume were measured using one repetition maximum and computed tomography, respectively. Differences were compared among ACE genotype groups (II vs. ID+DD) by sex and race. Results: Baseline and post-training, skeletal muscle strength and volume were not significantly correlated with ACE genotype. ACE genotype was significantly associated with muscle hypertrophy in Caucasian males only (p=0.02). Conclusions: The ACE genotype was not associated with skeletal muscle strength, but was associated with muscle hypertrophy in Caucasian males.
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    The Effects of Strength Training on Regional Body Composition in Older Adults: Sex and Race Comparisons
    (2007-05-22) Walts, Cory; Hurley, Ben F; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Purpose: To examine the influence of sex and race on the effects of strength training (ST) on thigh muscle volume (MV), mid-thigh subcutaneous fat (SCF) and intermuscular fat (IMF). Methods: One hundred and eighty-one previously inactive healthy Caucasian (N=117), African-American (N=54), and other (N=10) men (N=82) and women (N=99), aged 50-85 yrs, underwent ~10 weeks of unilateral knee extension ST. Results: Training-induced increases in absolute MV were significantly greater (P < 0.01) in men than in women. There were significant increases in MV within each race (P < 0.001); but no significant differences between races. There were no significant changes in SCF and IMF whether sex and racial groups were separated or combined. In addition, there was no sex by race interaction for changes in MV, SCF, or IMF with ST. Conclusion: Ten weeks of unilateral strength training does not alter subcutaneous or intermuscular fat regardless of sex or racial differences. Although men exhibit a greater muscle hypertrophic response to strength training compared to women, the difference is small. Race does not influence this response.