Theses and Dissertations
This collection includes both ASU Theses and Dissertations, submitted by graduate students, and the Barrett, Honors College theses submitted by undergraduate students.
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- All Subjects: Health Sciences
- Creators: Dickinson, Jared M
Description
Cardiovascular disease and diabetes are major health burdens. Diabetes is a primary risk factor of cardiovascular disease, and there is a strong link between obesity and risk of developing diabetes. With the prevalence of prediabetes highest among overweight/obese individuals, investigation into preventative strategies are needed. Aerobic exercise is a potent stimulus for both insulin and non-insulin dependent glucose uptake into the skeletal muscle. A single exercise session can improve insulin sensitivity within hours after exercise. The effects of intensity, type, and volume of exercise on glucose homeostasis have been studied extensively; however, controlling for muscle contraction frequency with a constant exercise intensity and workload has not been examined. The purpose of this study was to compare muscle contraction frequency during aerobic exercise by altering cycling cadence on insulin sensitivity and vascular health. Eleven obese males (age=28yr, BMI=35kg/m2) completed three conditions in random order: 1) control-no exercise; 2) 45-min cycling at 45 revolutions per minute (45RPM) at 65-75%VO2max; 3) 45-min cycling at 90RPM at 65-75%VO2max. Glucose control and insulin sensitivity were assessed with oral glucose tolerance tests (OGTT) 4 hours post-exercise. Vascular health was assessed via flow-mediated dilation (FMD) pre-exercise, 1-hr and 2-hr post exercise and ambulatory blood pressure was assessed pre-exercise, and continually every 15 min post-exercise. Linear mixed models were used to compare the mean differences in outcome variables. There were no significant differences found between control and both exercise conditions for all OGTT outcomes and no differences were found between control and exercise in FMD (all, p>0.05). Significant effects for exercise were found for both brachial and central blood pressure measures. Brachial systolic blood pressures were lower at 2- and 4-hr post-exercise by approximately -10 and -8mmHg, respectively (p<0.001 and p=0.004) versus control. Central systolic blood pressures were lower at 2-, 3-, and 4-hr post-exercise by approximately -8, -9 and -6mmHg, respectively (p<0.001, p=0.021 and p=0.004) versus control. In conclusion, aerobic exercise, regardless of muscle contraction frequency, were unable to effect glucose control and insulin sensitivity. Similarly, there was no effect on vascular function. However, there was a significant effect of aerobic exercise on reducing post-exercise blood pressure.
ContributorsJarrett, Catherine Lee (Author) / Gaesser, Glenn A (Thesis advisor) / Angadi, Siddhartha S (Committee member) / Dickinson, Jared M (Committee member) / Whisner, Corrie M (Committee member) / Todd, Michael W (Committee member) / Arizona State University (Publisher)
Created2017
Description
Exercise serves as a powerful stimulus to induce skeletal muscle adaptation. For instance, it is well understood that aerobic exercise (AE) elicits an adaptive response ultimately leading to increased fatigue resistance and capillarization, whereas resistance exercise (RE) is known to elicit an adaptive response leading to increased muscle strength and size. However, the precise molecular mechanisms mediating these unique adaptations to different forms of exercise remain to be completely resolved. The purpose of this study was to investigate the adaptive cellular response of skeletal muscle following acute AE and RE. Specifically, this study focused on two molecular processes: 1) mammalian/mechanistic target of rapamycin (mTOR) signaling pathway, a regulator of muscle protein synthesis, and 2) autophagy, a process through which proteins and organelles are broken down in the muscle fiber. In a counterbalanced, crossover design, six healthy, recreationally active young men (27±3 yr) completed acute AE (40 min of cycling ~70% maximal HR) and acute RE [8 sets, 10 reps, ~65% 1-repetition maximum (1RM)] separated by ~1wk. Muscle biopsies (vastus lateralis) were obtained before, at 1 and 4h post exercise and western blot analyses were used to examine the phosphorylation of mTOR signaling proteins and various markers of autophagy. Phosphorylation of mTORSer2448 increased only following RE at 4h (P < 0.05). However, phosphorylation of p70S6K1Thr389, a downstream marker of mTOR, increased following both AE and RE at 4h (P < 0.05). However, p70S6K1Thr389 was phosphorylated to a greater extent at 1h following RE compared to AE (P < 0.05). LC3BII was decreased at 1h and 4h postexercise in response to both AE and RE (P < 0.05). These data indicate that both acute AE and RE stimulate, to some degree, mTOR signaling in skeletal muscle, a pathway associated with increased muscle protein synthesis. Further, based on markers examined in the current study, both acute AE and RE similarly stimulate autophagy, which is associated with muscle protein breakdown. These data indicate that, at least in the immediate hours post exercise, the unique adaptations to AE and RE exercise may be mediated through cellular pathways other than mTOR and autophagy.
ContributorsMazo, Corey (Author) / Dickinson, Jared M (Thesis advisor) / Carroll, Chad C (Committee member) / Angadi, Siddartha S (Committee member) / Arizona State University (Publisher)
Created2019
Description
Maximal oxygen uptake (VO2max) declines with age and is a predictor of morbidity and mortality risks. Due to these implications, accurate assessment and determination of VO2max are important for the older population. Without the presence of a VO2 plateau, secondary criteria are used to determine whether the test resulted in a maximal value. However, inconsistent secondary criteria do not account for intersubject variability. To circumvent this issue, a verification phase following a traditional ramp assessment may be utilized. The purpose of this study was to compare verification phase strategies in older adults. A secondary purpose of this study was to examine the repeatability of the ramp assessment performed during each visit. Twenty-two older adults between 60 and 80 years of age were recruited to participate in the study. Each subject completed two experimental trials in a randomized, counterbalanced cross-over design. Both trials consisted of a ramp test and verification phase at either 85% (VP85) or 110% (VP110) of the peak work rate achieved during the ramp (Ramp85 and Ramp110, respectively). Expired gases and heart rate (HR) were monitored continuously and measured every ten seconds. VO2peak was determined by the highest 30-second averages for the ramp and verification phases. No significant differences were observed for absolute (L/min) VO2peak between VP85 (P = 0.679) or VP110 (P = 0.200) and the associated ramp. There was also no significant difference in maximal HR between VP85 (P = 0.243) or VP110 (P = 0.085) and the associated ramp. However, individual data shows that 36% of individuals achieved a 2% greater VO2 (L/min) during the VP85 compared to the Ramp85, while only 15% of subjects achieved a 2% greater VO2 (L/min) during the VP110 compared to Ramp110. No significant differences (P < 0.05) were found for most variables between Ramp1 and Ramp2. These data suggest that if a verification phase is employed for VO2max assessment in otherwise healthy older adults, a power slightly below peak work rate may provide a more accurate assessment compared to a power slightly above peak work rate.
ContributorsVillanueva, Ian Robert (Author) / Dickinson, Jared M (Thesis advisor) / Gaesser, Glenn A (Committee member) / Angadi, Siddhartha S (Committee member) / Arizona State University (Publisher)
Created2019