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ABSTRACT Despite significant advancements in drug therapy, cardiovascular disease (CVD) is still the leading cause of death in the United States. Given this, research has begun to seek out alternative approaches to reduce CVD risk. One of these alternative approaches is Vitamin D supplementation. Current research has shown a link between Vitamin D status and CVD risk in both healthy and diseased populations. Among the possible mechanisms is a positive effect of Vitamin D on vascular endothelial function, which can be measured with noninvasive techniques such as flow-mediated dilation (FMD) of conduit vessels using high-resolution ultrasound. This dissertation is comprised of two studies. The first examines whether Vitamin D supplementation can improve FMD in older adults within a time period (two weeks) associated with peak increases in plasma Vitamin D concentrations after a single-dose supplementation. The second examines the effect of Vitamin D supplementation in people with Rheumatoid Arthritis (RA). The reason for looking at an RA population is that CVD is the leading cause of early mortality in people with RA. In the first study 29 Post-Menopausal Women received either 100,000 IU of Vitamin D3 or a Placebo. Their FMD was measured at baseline and 2 weeks after supplementation. After 2 weeks there was a significant increase in FMD in the Vitamin D group (6.19 + 4.87 % to 10.69 + 5.18 %) as compared to the Placebo group (p=.03). In the second study, 11 older adults with RA were given 100,000 IU of Vitamin D or a Placebo. At baseline and one month later their FMD was examined as well as plasma concentrations of Vitamin D and tumor necrosis factor-alpha; (TNF-alpha;). They also filled out a Quality of Life Questionnaire and underwent a submaximal exercise test on the treadmill for estimation of maximum oxygen uptake (VO2max). There was no significant change in FMD in Vitamin D group as compared to the Placebo group (p=.721). Additionally, there was no significant improvement in either plasma Vitamin D or TNF-alpha; in the Vitamin D group. There was however a significant improvement in predicted VO2max from the submaximal exercise test in the group receiving Vitamin D (p=.003). The results of these studies suggest that a single 100,000 IU dose of Vitamin D can enhance FMD within two week in older adults, but that a similar dose may not be sufficient to increase FMD or plasma Vitamin D levels in older adults with RA. A more aggressive supplementation regimen may be required in this patient population.
Although maintaining an optimal level of muscle quality in older persons is necessary to prevent falls and disability, there has been limited research on muscle quality across age and gender groups. The associations of muscle quality, muscle strength, and muscle mass also remain less explored. Purpose: This study examined the muscle quality differences (arm and leg) between healthy young and elderly adults across gender groups. This study also examined the associations of muscle quality, muscle strength, and muscle mass in young and elderly adults, respectively. Methods: Seventy-one total subjects were recruited for this study within age groups 20-29 years old (20 females and 20 males) and 60-80 years old (18 females and 13 males). All participants completed anthropometric measures, dual-energy x-ray absorptiometry, pulse wave velocity, handgrip strength and leg strength tests, gait speed, and sit to stand test. Results: Young male adults had a greater leg muscle quality index (leg MQI) than did elderly male adults (21.8 Nm/kg vs. 16.3 Nm/kg, p = 0.001). Similarly, young female adults had a greater leg MQI than did old female adults (21.3 Nm/kg and 15.6 Nm/kg, p<0.001). For arm muscle quality index (arm MQI), there was a gender difference in young adults (p = 0.001), but not for the elderly adults. Among elderly adults, there was a positive association between leg MQI and isometric leg strength (r = 0.79, p<0.001). Notably, there was a negative association between leg MQI and leg lean mass (r = -0.70, p<0.001) and between arm MQI and arm lean mass (r = -0.58, p = 0.001). In young adults, there was also a positive association between arm MQI and handgrip strength (r = 0.53, p<0.001) and between leg MQI and isometric leg strength (r = 0.81, p<0.001). There was no association between muscle quality and muscle mass in young adults. Conclusion: Young adults had a greater leg muscle quality than did elderly adults in both men and women. Leg muscle quality is positively associated with leg muscle strength in both young and elderly adults but is inversely associated with leg muscle mass in the elderly adults.
Commitment to an activity is widely studied in leisure research. Serious Leisure Perspective (SLP) describes characteristics a committed activity participant possesses. The Psychological Continuum Model (PCM) describes the psychological process a person goes through to become committed to a leisure activity. Awareness, attraction, attachment and loyalty make of the four stages of PCM. Both perspectives have been used to describe committed leisure activity participants and commitment to organized recreational events. Research on leisure activity has yet to determine how the individual becomes loyal. Therefore, the purpose of this study is to determine the process in which recreation activity participates becomes loyal and to identify who can be labels as serious within the PCM Framework. Data was obtained from an online electronic survey distributed to participants of four U.S. marathon and half marathon events. A total of 579 responses were used in the final analysis. Path analysis determined the process in which a runner becomes committed. MANOVA is used to determine difference between leisure groups in the four stages of PCM. Results indicate that activity participants need to go through all four stages of PCM before becoming loyal. As knowledge increases, individuals are more motivated to participate. When the activity satisfies motives and becomes a reflection of their identity, feelings become stronger which results in loyalty. Socialization is instrumental to the progression through the PCM Framework. Additionally, attachment is the "bottleneck" in which all loyal activity participants my pass through. Differences exist between serious leisure groups in the attachment and loyalty stages. Those that are `less serious' are not as committed to the activity as their counterparts.