Muscle strain injuries affect a wide range of physically active people around the world and are reaching epidemic proportions. Despite the variety of treatment options available in rehabilitation, there are no clear guidelines for electrical stimulation that provide effective reproducible results that address the underlying cause of these injuries. For instance, electrotherapy is inefficient at stimulating muscles, because of imprecise parameters and an ability to target particular muscles. The difference between this study and previous research is the precise delivery of electrical stimulation (intramuscular) at two different frequencies (2 Hz and 50 Hz) and comparing it a control group. Objective: To determine the difference on muscle strength and functional status between three treatments modalities for sub acute and chronic hamstring strains. Design: A randomized experimental design was used to compare the effects of low (2 Hz), high (50 Hz) and no-electrical (control) intramuscular stimulation on muscle strength and mental and functional status (AMSMC HEALTH STATUS INDEX). Each group consisted of 18 subjects. Main Outcome: The difference in treatment modalities was evaluated by comparing the muscle strength test (Biodex Dynamometer) results and the AMSMC HEALTH STATUS INDEX results in pretest and post-test conditions. Results: The AMSMC HEALTH STATUS INDEX, but not muscle strength test (Biodex), changed significantly after 2-Hz electrical intramuscular stimulation (pre-test µ = 66.56, Std= 11.92, post-test µ= 92.89, Std= 6.25), whereas no statistically significant changes in health status index and muscle strength test occurred with 50-Hz (pre-test = 69.22, Std= 11.31, post-test µ= 70.22, Std= 12.27)) and no-electrical stimulation groups (pre-test µ= 69.11, post-test µ= 73.39, Std= 13.18).

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Poly(methyl methacrylate) (PMMA) and polystyrene (PS), which are fully amorphous polymers, have been extensively studied for over a decade to discover how their mechanical behaviours vary with temperatures and strain rates. In this study, Mechanical tests were carried out at a range of strain rates and temperatures using a Hounsfield H50KM Test Machine wluch provides quasi- static rates (10-4 - 10-3 S-l) and low strain rates (10-2 - 10-1 S-l), and an in-house built Dropweight Machine which provides high strain rates (102 - 103 S-l) Mechanical tests were also performed in a high-speed photographic system, which provides high strain rates (103 S-l), to visualise the deformation of the polymers at a range of temperatures. An aluminium-heating block was built to heat up the samples to the required temperature. Strain limited tests were carried out at a range of strain rates and temperatures. Differential Scanning Calorimetry (DSC) was employed to study the glass transition temperatures and the specific heats of the samples. Dynamic Mechanical Thermal Analysis (DMTA) was adopted to study the transitions in the samples and the change of moduli with temperature densities of samples before and after high strain rate compression at certain strain were measured using a Six Column Density Apparatus The polarising microscope was used to study the orientation of the polymer chains at a range of temperatures, strains and strain rates. Eyring's theory of viscous flow was applied on yield point, 20% and 30% strain to relate the activation energy and volume with strain rate and temperature from the thermodynamic perspective. Temperature rise was calculated for high strain rate data to fit into the isothermal curve for the application of Eyring's theory and to obtain the actual smnple temperature at which the deformation took place. PMMA and PS showed ductile behaviour when tested at quasi-static and low strain rates at temperatures below their ductile-brittle transition temperatures. The densities of samples were not found to increase at different strains. The orientations of polymer chains did not influence the increase at Yield stress at high strain rates. The interpretation of activation energy and volume provided information of how the flows of chains took place at different temperatures and strain rates.

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Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: Joseph M. Fox, Dept. of Chemistry & Biochemistry. Includes bibliographical references.

Thesis (M.S. in Aeronautical Engineering)--Naval Postgraduate School, September 2002. / Thesis advisor(s): Ramesh Kolar, E. Roberts Wood. Includes bibliographical references (p. 113). Also available online.

Thesis (M.S. in Aeronautical Engineering)--Naval Postgraduate School, September 2002. / Thesis advisor(s): Raymond P. Shreeve, Garth V. Hobson. Includes bibliographical references (p. 93). Also available online.

Muscle strain injuries affect a wide range of physically active people around the world and are reaching epidemic proportions. Despite the variety of treatment options available in rehabilitation, there are no clear guidelines for electrical stimulation that provide effective reproducible results that address the underlying cause of these injuries. For instance, electrotherapy is inefficient at stimulating muscles, because of imprecise parameters and an ability to target particular muscles. The difference between this study and previous research is the precise delivery of electrical stimulation (intramuscular) at two different frequencies (2 Hz and 50 Hz) and comparing it a control group. Objective: To determine the difference on muscle strength and functional status between three treatments modalities for sub acute and chronic hamstring strains. Design: A randomized experimental design was used to compare the effects of low (2 Hz), high (50 Hz) and no-electrical (control) intramuscular stimulation on muscle strength and mental and functional status (AMSMC HEALTH STATUS INDEX). Each group consisted of 18 subjects. Main Outcome: The difference in treatment modalities was evaluated by comparing the muscle strength test (Biodex Dynamometer) results and the AMSMC HEALTH STATUS INDEX results in pretest and post-test conditions. Results: The AMSMC HEALTH STATUS INDEX, but not muscle strength test (Biodex), changed significantly after 2-Hz electrical intramuscular stimulation (pre-test µ = 66.56, Std= 11.92, post-test µ= 92.89, Std= 6.25), whereas no statistically significant changes in health status index and muscle strength test occurred with 50-Hz (pre-test = 69.22, Std= 11.31, post-test µ= 70.22, Std= 12.27)) and no-electrical stimulation groups (pre-test µ= 69.11, post-test µ= 73.39, Std= 13.18). / Education, Faculty of / Kinesiology, School of / Graduate

No description available.