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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Item Cardiorespiratory Fitness as a Moderator of Sleep-Related Associations with Hippocampal Volume and Cognition(MDPI, 2022-10-07) Alfini, Alfonso J.; Won, Junyeon; Weiss, Lauren R.; Nyhuis, Casandra C.; Zipunnikov, Vadim; Spira, Adam P.; Liu-Ambrose, Teresa; Shackman, Alexander J.; Smith, J. CarsonThe objective of this study was to understand the associations of sleep and cardiorespiratory fitness with hippocampal volume and global cognition among older adults (n = 30, age = 65.8 years, female = 73.3%). Wrist actigraphy provided objective measures of nighttime sleep including sleep duration, average wake bout length (WBL; sleep disturbance), and wake-to-sleep transition probability (WTSP; sleep consolidation). Cardiorespiratory fitness was quantified via cycle exercise using a modified heart rate recovery approach. Magnetic resonance imaging was used to determine hippocampal volume and the Mini-Mental State Examination was used to assess global cognition. Fitness moderated associations of sleep with hippocampal volume and cognitive performance, whereby the association of WBL—an index of poor sleep—with hippocampal atrophy was stronger among less-fit individuals, and the association of sleep duration with cognitive performance was stronger among more-fit individuals. Across the fitness levels, a longer WBL was associated with lower cognitive performance, and a higher WTSP—an index of more consolidated sleep—was associated with greater hippocampal volume. Sleep and fitness were unrelated to the volume of an amygdala control region, suggesting a degree of neuroanatomical specificity. In conclusion, higher cardiorespiratory fitness may attenuate sleep disturbance-related hippocampal atrophy and magnify the cognitive benefits of good sleep. Prospective studies are needed to confirm these findings.Item BARRIERS OF AGING: THE IMPACT OF HOUSING ON U.S. OLDER ADULT HEALTH(2020) Hall, Quinshay; Roby, Dylan H; Health Services Administration; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Today, millions of older adults aged 65 and older, face the challenges of aging. In the past ten years, the number of people aged 65 and older in the U.S. increased from 37.2 million to 49.2 million, and by 2040 an estimated one in five Americans will be age 65 or older (Administration for Community Living & Administration on Aging, 2018; Urban Institute, 2014). Housing is a significant factor in health outcomes for this population because of their increased time spent in the home, which can put them at an increased risk for home accidents (Newman, 2003). Using the Health and Retirement Study, this study explores the association of assistive features being present in one’s home on health status and provides evidence to identify the housing needs of the older adult population.Item INVESTIGATING SOURCES OF AGE-RELATED DIFFERENCES IN WALKING MECHANICS(2019) Krupenevich, Rebecca Lynn; Miller, Ross H.; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Walking is one of the most common activities of daily living and represents independence and improved quality of life, particularly among older adults. However, many older adults report substantial mobility challenges, which may be associated with age-related differences in lower-extremity gait kinetics. These differences are summarily referred to as a ‘distal to proximal shift’ of joint moments and powers, and are characterized by smaller ankle kinetics and larger hip kinetics in older vs. young adults. Although age-related differences in walking mechanics are well-documented, there is little consensus about which biomechanical factors contribute to these differences. Addressing this gap in knowledge is an important step in determining if this shift is preventable, or rather, an unavoidable part of healthy aging. Therefore, the overarching goal of this dissertation was to investigate sources of the age-related distal to proximal shift in gait kinetics. Specifically, this dissertation determined the extent to which the shift in kinetics is explained by age-related differences in (i) step length and trunk kinematics, (ii) years of endurance running (i.e., habitual physical activity), and (iii) gastrocnemius muscle architecture and individual lower-extremity muscle forces. In study 1, step length and trunk position did not reverse or reduce the age-related distal to proximal shift. Similarly, in study 2, a history of habitual endurance running did not reduce or reverse the shift. The third study confirmed the distal to proximal shift at the muscle level, suggesting that gastrocnemius may be a primary site of age-related differences in plantarflexor force, due to the shorter gastrocnemius muscle fascicles and smaller gastrocnemius force production in older adults vs. young adults. The present findings support the notion that the age-related distal to proximal shift of kinetics in active older adults is due primarily to differences at the muscle level and do not support previous speculations that this shift is due to spatiotemporal factors such as step length, joint kinematics, or physical activity. Further, these results suggest that age-related differences in lower-extremity joint kinetics are an unavoidable part of natural aging even in the absence of mobility limitations and the presence of a lifelong history of endurance running.Item The Effect of a 10 day Cessation of Training in Older Endurance Athletes on Pathological Production of Nitric Oxide and Reactive Oxygen Species Levels in Circulating Angiogenic Cells(2015) Corrigan, Kelsey J.; Hagberg, James; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Cardiovascular disease (CVD) is a serious disease, and is the leading cause of death in the United States. Aging and physical inactivity are two well-established risk factors for CVD. Previous research has identified circulating angiogenic cells (CACs) as a novel risk factor for CVD. CAC number and function are affected by aging and exercise. Nitric oxide (NO) and reactive oxygen species (ROS) are intracellular compounds which can affect the health of the vasculature and are also affected by exercise. Endothelial nitric oxide synthase (eNOS) is responsible for NO production within the endothelium, and eNOS "coupling" is a phenomenon that plays a role in the balance between production of ROS and NO. The literature also indicates that NO can be produced in either a pathological or physiological capacity depending on which isoform of NOS produces it. NO and ROS have been previously measured in CACs and have been shown to affect in vivo and in vitro outcomes related to vascular function. Although NO, ROS, and CACs have all been studied in relation to exercise, no previous studies have examined how the cessation of training in older endurance-trained athletes affects these intra-cellular compounds through the eNOS-coupling pathway. The purpose of this study was to examine the effect of a 10-day cessation of exercise training in older endurance-trained athletes on ROS, NO and the eNOS-coupling pathway in CD34+ cells. NO and ROS were measured in isolated fresh CD34+ cells using fluorescent dye assays. The mRNA expression of genes involved in the eNOS-coupling pathway (endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), dihydrofolate reductase (DHFR), and guanosine triphosphate cyclohydrolase 1 (GTPCH1)) were measured using semi-quantitative Polymerase Chain Reaction (Semi-qt PCR). Flow mediated dilation was measured to gain information about endothelial function. No significant differences were detected after the cessation of training in CD34+ intracellular NO or ROS levels. Flow mediated dilation (FMD) also did not change significantly following cessation of training. eNOS mRNA expression was significantly lower following cessation of training but iNOS, DHFR, and GTPCH1 did not change. Taking into consideration the current literature, we expected to see changes in all of the above variables with the cessation of exercise training. There were several limitations present in our study, which could have affected our outcomes. Research in this area, specifically the eNOS coupling pathway, is still very new and this study shows that additional research is still needed to elucidate the underlying mechanisms in CACs.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 The Dynamics of Multi-sensory Re-weighting in Healthy and Fall-prone Older Adults(2006-08-04) Allison, Leslie K.; Jeka, John J.; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Multi-sensory re-weighting (MSR) is an adaptive process that prioritizes the visual, vestibular and somatosensory inputs that provide the most reliable information when environmental conditions change. This process is thought to degrade with increasing age, and to be particularly deficient in fall-prone versus healthy older adults. This dissertation presents three studies designed to investigate age- and fall-related changes in MSR. The first study examined the assumption of impaired MSR in healthy and fall-prone older adults using a two-frequency touch/vision experimental design with stimuli at varying amplitudes. Both healthy and fall-prone older adults demonstrated the same pattern of adaptive gain changes as healthy young adults. No group differences in the overall levels of vision and touch gain were found. These results suggest that, for small amplitude vision and touch stimuli, the central sensory re-weighting adaptation process remains intact in healthy and fall-prone older adults. In the second study the effects of a sensory-challenge balance exercise program on laboratory measures of MSR and clinical measures of balance were investigated. Following the intervention the normal adaptive pattern of gain change was unaltered, while declines in overall vision and touch gains that reflect down-weighting of the sensory stimuli were seen. Improvements in four clinical balance measures were observed. These findings indicate that MSR processes in fall-prone older adults are modifiable, that sensory challenge balance exercises may facilitate the ability to down-weight unstable sensory inputs, and that these effects may generalize to other components of balance. A third study explored the dynamics of sensory re-weighting in healthy and fall-prone older adults. Absolute levels of gain, and the rate of adaptive gain change, were examined before and after large changes in visual motion stimulus amplitude. Compared to young adults, gains in both older adult groups were higher when the stimulus amplitude was high, and gains in the fall-prone elderly were higher than both other groups when the stimulus amplitude was low. Both older groups demonstrated slowed sensory re-weighting over prolonged time periods when the stimulus amplitude was high. These results reflect age- and fall-related changes in the extent and rate of down-weighting unstable visual inputs.Item EFFECT OF ENDURANCE EXERCISE TRAINING ON FASTING AND POSTPRANDIAL PLASMA ADIPONECTIN LEVELS(2005-07-12) Brandauer, Josef; Hagberg, James M; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The purpose of this study was to investigate the postprandial response of plasma adiponectin (AN) levels to a high-calorie, high-fat meal, in relatively healthy (free of diabetes, overt heart disease) sedentary 50- to 75-year-old men and women before and after a six-month endurance exercise training program (approximately 70% of VO2 max, three times per week). AN is an adipocyte-released polypeptide ("adipokine") whose physiological significance in insulin sensitivity and other health risk factors is well documented. VO2 max was significantly increased with training in both men and women (men, 27.0 ± 0.9 vs. 32.2 ± 1.2 mL/kg/min, p < 0.0001; women, 23.3 ± 1.0 vs. 27.1 ± 1.4 mL/kg/min, p = 0.0002), while % body fat was decreased (men, 29.9 ± 1.2 vs. 26.0 ± 1.3 %, p = 0.0010 ; women, 42.3 ± 1.5 vs. 39.5 ± 1.8 %, p < 0.0001). Fasting AN levels were higher in women than in men (gender main effect, p = 0.0138), and fasting as well as postprandial adiponectin levels decreased significantly with training in men (p = 0.014) but not in women. No postprandial changes in plasma AN levels were observed in either gender. Stepwise regression analysis showed insulin sensitivity to be the strongest predictor of fasting AN levels. Postprandial AN levels were mainly dependent on fasting AN concentrations. In conclusion, fasting plasma adiponectin levels decreased with exercise training in men in the present study, whereas they remained unchanged in women. Postprandial adiponectin levels did not change following consumption of a high-fat meal either before or after exercise training.