Thesis (M.A.)--University of Alabama at Birmingham, 2009. / Title from PDF title page (viewed Jan. 28, 2010). Includes bibliographical references (p. 23-24).

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Age-related muscle atrophy and the importance of satellite cells in muscle maintenance, growth and repair led us to examine the effects of mechanical stretch, nitric oxide (NO), and age on satellite cell (SC) activation and gene expression in normal young and old mice. Baseline variables (body mass, muscle mass, fiber cross-sectional area (CSA), muscle strength, SC population, stretch activation and gene expression) were obtained from normal C57BL/6 mice at 3-, 8-, 12- and 18-months-of-age. Activation was assayed by 3H-thymidine incorporation into extensor digitorum longus (EDL) muscles isolated for culture. In a second experiment, muscle from 8- and 18-month-old mice was treated with one or more of: stretch; NO-donors (L-Arginine (LA), isosorbide dinitrate (ISDN)) and; Nω-nitro-L-Arginine methyl ester (LN). EDL muscles from 6-month-old mice required a greater stretch stimulus (20% vs. 10% length increase) than EDL from younger mice to increase SC activation. Stretch did not increase SC activation in mice older than 6 months-of-age. NO supplementation from an exogenous source (ISDN) increased SC activation by stretch in 8- but not 18-mo-old EDLs. In a third experiment, 8- and 18-month-old mice were subjected to 3 weeks of voluntary wheel running, or not. The EDL, tibialis anterior (TA), gastrocnemius (GAST) and quadriceps (QUAD) muscles were selected for analysis following sacrifice. The QUAD muscle from 8-month-old mice was the only muscle that demonstrated an exercise-induced increase in SC activation, elevated expression of neuronal nitric oxide synthase (NOS-I) and downregulation of myostatin, a gene that inhibits muscle growth. These results suggest mechanical stimulation of satellite cells and regulation of gene expression that controls muscle growth in voluntary contractile tissue is muscle-specific and age-dependent.

The monotonous and strenuous shoulder moving pattern during throwing may result in microtrauma and fibrous adhesions between the layers of fascia among athletes. In the last decade, self myofascial release (SMR) has gained good reputation as a way to treat these adhesions. However, there is limited data demonstrating the effects on upper body performance among athletes. PURPOSE: The purpose was to examine the effects from an acute bout of upper body SMR or from dynamic stretch (DS), on shoulder range of motion (ROM), throwing velocity and throwing accuracy. Also to examine correlations between shoulder ROM and throwing velocity/accuracy and between playing experience (PE) and changes in throwing velocity/accuracy and ROM. METHODS: 20 elite male handball players (age 20 ± 5 years, weight 84 ± 9 kg) were included in the study. The study had an experimental cross-over design in which participants first performed baseline measures. They also performed SMR and DS in two different trials. The trials were supervised and separated by 14 days. During SMR, the athletes performed a series of foam rolling exercises during two minutes for the muscles surrounding the shoulder joint. The same muscles were stretched for two minutes during the DS trial. Directly after foam rolling and DS, shoulder ROM, throwing velocity and throwing accuracy were measured using a gravity reference goniometer, radar gun and a high speed videocamera. ANOVA with repeated measures and t-tests were used to analyze differences between and within groups. RESULTS: There were no statistically significant differences in either shoulder ROM, throwing velocity or throwing accuracy between the three trials. There was a moderate correlation between shoulder extension and mean accuracy (r = 0.62; p = 0.004) after DS. When dividing the group into high and low experienced players, among the players in the PE-low group, the most experienced players elicited the greatest increase in peak throwing velocity after DS (r = 0.58; p = 0.10). Change in peak accuracy showed moderate but conflicting correlations after SMR (r = -0.53; p = 0.09) and DS (r = 0.50; p = 0.11) for the players in the PE-high group, indicating a better result after SMR. CONCLUSION: An acute bout of upperbody SMR does not affect ROM and does not improve throwing velocity or throwing accuracy compared to baseline or DS among elite male handball players. Nor could any correlation between ROM and throwing velocity or throwing accuracy be observed. The associations between PE and throwing performance was inconclusive. Further studies is needed to define if PE should be taken into consideration when using SMR or DS in order to improve throwing performance.

The propagation of premixed flames in turbulent flows is a problem of wide physical and technological interest, with a significant literature on their propagation speed and front topology. While certain scalings and parametric dependencies are well understood, a variety of problems remain. One major challenge, and focus of this thesis, is to model the influence of fuel/oxidizer composition on turbulent burning rates. Classical explanations for augmentation of turbulent burning rates by turbulent velocity fluctuations rely on global arguments - i.e., the turbulent burning velocity increase is directly proportional to the increase in flame surface area and mean local burning rate along the flame. However, the development of such global approaches is complicated by the abundance of phenomena influencing the propagation of turbulent premixed flames. Emphasizing key governing processes and cutting-off interesting but marginal phenomena appears to be necessary to make further progress in understanding the subject. An alternative approach to understand turbulent augmentation of burning rates is based upon so-called "leading points", which are intrinsically local properties of the turbulent flame. Leading points concepts suggest that the key physical mechanism controlling turbulent burning velocities of premixed flames is the velocity of the points on the flame that propagate farthest out into the reactants. It is postulated that modifications in the overall turbulent combustion speed depend solely on modifications of the burning rate at the leading points since an increase (decrease) in the average propagation speed of these points causes more (less) flame area to be produced behind them. In this framework, modeling of turbulent burning rates can be thought as consisting of two sub-problems: the modeling of (1) burning rates at the leading points and of (2) the dynamics/statistics of the leading points in the turbulent flame. The main objective of this thesis is to critically address both aspects, providing validation and development of the physical description put forward by leading point concepts. To address the first sub-problem, a comparison between numerical simulations of one-dimensional laminar flames in different geometrical configurations and statistics from a database of direct numerical simulations (DNS) is detailed. In this thesis, it is shown that the leading portions of the turbulent flame front display a structure that on average can be reproduced reasonably well by results obtained from model geometries with the same curvature. However, the comparison between model laminar flame computations and highly curved flamelets is complicated by the presence of negative (i.e., compressive) strain rates, due to gas expansion. For the highest turbulent intensity investigated, local consumption speeds, curvatures, strain rates and flame thicknesses approach the maximum values obtained by the laminar model geometries, while other cases display substantially lower values. To address the second sub-problem, the dynamics of flame propagation in simplified flow geometries is studied theoretically. Utilizing results for Hamilton-Jacobi equations from the Aubry-Mather theory, it is shown how the overall flame front progation under certain conditions is controlled only by discrete points on the flame. Based on these results, definitions of leading points are proposed and their dynamics is studied. These results validate some basic ideas from leading points arguments, but also modify them appreciably. For the simple case of a front propagating in a one-dimensional shear flow, these results clearly show that the front displacement speed is controlled by velocity field characteristics at discrete points on the flame only when the amplitude of the shear flow is sufficiently large and does not vary too rapidly in time. However, these points do not generally lie on the farthest forward point of the front. On the contrary, for sufficiently weak or unsteady flow perturbations, the front displacement speed is not controlled by discrete points, but rather by the entire spatial distribution of the velocity field. For these conditions, the leading points do not have any dynamical significance in controlling the front displacement speed. Finally, these results clearly show that the effects of flame curvature sensitivity in modifying the front displacement speed can be successfully interpreted in term of leading point concepts.

Background: Self-myofascial release is widely used by athletes but the scientific evidence of its supposedly positive effects is limited. This study was conducted to investigate the effects of foam rolling as a warm-up routine in comparison with a dynamic stretching routine and how it may affect the jumping performance among subjects familiar with weight training. Aim: The aim of this study was to investigate the acute effect of foam rolling vs. a standardized dynamic stretch warm-up routine on jumping performance. Method: Twelve subjects, mean (SD) age 25.1 (± 3.0) years, participated in a randomized, controlled, crossover study. All subjects completed a standardized foam rolling (FR) and a dynamic stretch (DS) warm-up routine on separate days of testing. Squat jump (SJ), counter movement jump (CMJ) and loaded counter movement jump (L-CMJ) all performed bilaterally and unilaterally were conducted to investigate the acute effect of the two warm-up routines. A dependent T-test was used to investigate differences between the warm-up routines. Results: A statistical significant difference in favor of the DS was found for SJ performed bilaterally among males (p = 0.009). The mean (SD) jumping height for SJ FR was 35.6 (± 4.7) cm and for SJ DS 37.9 (± 5.2) cm. The male group also improved more in L-CMJ performed on the right leg with an external load of 54kg after DS compared to FR. No other statistical significant differences were found between the two interventions. A near statistical significant difference was found for SJ performed bilaterally for the total sample (p = 0.057) also in favor of the DS. The mean (SD) jumping height for SJ FR was 29.3 (± 8.7) cm and for SJ DS 30.5 (± 9.9) cm. Conclusion: Findings from this study supports a dynamic stretch warm-up routine prior to performing high intensity bilateral plyometrics instead of a foam rolling warm-up routine. However the data was inconsistent and more research with larger sample sizes is needed to further investigate the possible effects of foam rolling as a warm-up routine on jumping performance performed both bilaterally and unilaterally.

Age-related muscle atrophy and the importance of satellite cells in muscle maintenance, growth and repair led us to examine the effects of mechanical stretch, nitric oxide (NO), and age on satellite cell (SC) activation and gene expression in normal young and old mice. Baseline variables (body mass, muscle mass, fiber cross-sectional area (CSA), muscle strength, SC population, stretch activation and gene expression) were obtained from normal C57BL/6 mice at 3-, 8-, 12- and 18-months-of-age. Activation was assayed by 3H-thymidine incorporation into extensor digitorum longus (EDL) muscles isolated for culture. In a second experiment, muscle from 8- and 18-month-old mice was treated with one or more of: stretch; NO-donors (L-Arginine (LA), isosorbide dinitrate (ISDN)) and; Nω-nitro-L-Arginine methyl ester (LN). EDL muscles from 6-month-old mice required a greater stretch stimulus (20% vs. 10% length increase) than EDL from younger mice to increase SC activation. Stretch did not increase SC activation in mice older than 6 months-of-age. NO supplementation from an exogenous source (ISDN) increased SC activation by stretch in 8- but not 18-mo-old EDLs. In a third experiment, 8- and 18-month-old mice were subjected to 3 weeks of voluntary wheel running, or not. The EDL, tibialis anterior (TA), gastrocnemius (GAST) and quadriceps (QUAD) muscles were selected for analysis following sacrifice. The QUAD muscle from 8-month-old mice was the only muscle that demonstrated an exercise-induced increase in SC activation, elevated expression of neuronal nitric oxide synthase (NOS-I) and downregulation of myostatin, a gene that inhibits muscle growth. These results suggest mechanical stimulation of satellite cells and regulation of gene expression that controls muscle growth in voluntary contractile tissue is muscle-specific and age-dependent.

Atrial fibrillation is the most common sustained arrhythmia; however, its mechanism is not well understood. Several conditions such as valvular disease, heart failure, and hypertension predispose to atrial fibrillation. Identifying the electrophysiological substrate in these clinical conditions would yield insight into the mechanism of atrial fibrillation and aid in developing strategies to prevent or cure it. Rheumatic mitral stenosis is associated with high prevalence of atrial fibrillation. While atrial stretch itself may be adequate to explain the occurrence of atrial fibrillation in this population, it is not known if the disease process would remodel the atria so as to increase its propensity. Chapters 2 and 3 present the results of the studies evaluating the substrate for atrial fibrillation in both the left and right atria in rheumatic mitral stenosis. These studies have demonstrated extensive conduction abnormalities both regional and site specific associated with low voltage area and scar. Despite the prolonged atrial refractoriness, the propensity for atrial fibrillation was increased; lending support to the theory that structural remodelling associated with conduction abnormalities plays a greater role in the substrate predisposing to atrial fibrillation. Chapters 4 and 5 present the results of the studies evaluating the immediate effects of chronic atrial stretch reversal on the atrial electrical remodelling. These studies demonstrated that immediately after percutaneous mitral commissurotomy there was decrease in P wave duration, improvement in site specific conduction delay and conduction velocity associated with increase in the voltage. However, there was no change in atrial refractoriness. Chapter 6 studies the substrate long-term after reduction of stretch. There was further increase in conduction velocity and voltage associated with decrease in atrial refractoriness and conduction delay across the crista terminalis. These observations suggest that strategies aimed at reducing atrial stretch in different disease conditions would potentially decrease the burden or prevent atrial fibrillation. There is mounting evidence of the effect of stretch on the atria; however, the effect of stretch on the triggers of atrial fibrillation has not been evaluated before. Chapter 7 and 8 present the results of the study examining the effect of acute and chronic stretch on human pulmonary veins. Simultaneous pacing of the right ventricle and pulmonary vein induced acute stretch. The effect of chronic stretch was evaluated in patients with mitral stenosis. The atrial refractoriness was abbreviated in acute stretch while it was prolonged in the chronic form. Nevertheless, both resulted in marked pulmonary vein conduction abnormalities that were pronounced with chronic stretch and extra-stimuli. Additionally, structural remodelling was seen with chronic stretch. These abnormalities implicate stretch in the milieu for re-entry and pulmonary vein arrhythmogenesis in conditions predisposed to atrial fibrillation. In summary, this thesis has evaluated the effects of stretch on the substrate and triggers of atrial fibrillation. It provides evidence for the importance of structural changes and the associated abnormalities in conduction in predisposing to atrial fibrillation. These observations may be important in the development of tools to treat, cure and prevent atrial fibrillation. / Thesis (Ph.D.) -- University of Adelaide, School of Medicine, 2008

Thesis (MHSc--Health Science) -- Auckland University of Technology, 2002. / Also held in print (80 leaves, col. ill., 30 cm.) in North Shore Theses Collection (T 612.76 TRE).

Thesis (M.S.)--Brigham Young University. Dept. of Exercise Sciences, 2004. / Includes bibliographical references (p. 53-58).