Magister Artium (Sport, Recreation and Exercise Science) - MA(SRES) / Hamstrings muscle injury is the most frequent soccer-related injury in amateur and professional soccer players. Despite various interventions, the risk of hamstrings re-injury remains high. Several scientific studies examined the potential risk factors and their contribution to the occurrence of hamstrings injuries in male soccer players. The aim of the study was to investigate the relationship between selected physical characteristics, such as time-to-peak torque, hip abduction peak torque, hamstrings-to-quadriceps strength ratio, and hamstrings flexibility and the occurrence of hamstrings injuries in amateur male soccer players. A prospective, quantitative cross-sectional study design was utilized in this study. A total of 89 amateur male soccer players aged 18-35 years were recruited from the Cape Town Football District to perform functional assessments before injury occurred, which included anthropometric measurements, an evaluation of lower extremity isokinetic muscle strength (both knee and hip) and hamstrings flexibility tests. Instruments used to measure the anthropometric data were a calibrated Seca balance beam scale and stadiometer, a skinfold caliper, a sliding caliper, an anthropometer (All Harpenden, UK) and a metal tape measure. The Biodex Pro System 4 isokinetic dynamometer was used to measure lower extremity isokinetic muscle strength and a goniometer to measure hamstrings flexibility. Descriptive statistics included means and standard deviations, and inferential statistics included Pearson product-moment correlation to determine the relationship between selected physical characteristics and the occurrence of hamstrings injuries. Multivariate logistic regression via the forward stepwise method was utilised to predict potential physical characteristics (risk factors) for hamstrings injury in amateur male soccer players. Statistical significance was a p value of below 0.05. The prevalence of hamstrings injury was 4.3 %, with the multivariate logistic regression analysis indicating that time-to-peak torque was a significant predictor of the occurrence of hamstrings injury (OR = 1; p = 0.027). In conclusion, time-to-peak torque was a significant predictor of the occurrence of hamstrings injury. The players with hamstrings injuries produced a significantly slower time-to-peak torque, which has relevance for soccer players and coaches in addressing this common injury at all levels of competition.

Nos últimos anos tem se dado uma evolução muito grande na área industrial de MEMS, e esta se caracteriza por desenvolvimento dos processos de microeletrônica para diminuição de custos e a própria integração de diferentes sistemas que passam a ser muito confiáveis em diferentes aplicações. Motivado pelas tendências de elevar os conhecimentos de processos para obtenção de MEMS, foi proposto um trabalho de corrosão anisotrópica de silício utilizando solução de hidróxido de potássio (KOH) junto com a adição de sais metálicos. O objetivo é comprovar o efeito de compensação cinética da reação e a influência destes metais no caráter anisotrópico e nas taxas de corrosão. Foi analisado o efeito de zinco, alumínio e cobre, e puderam ser observadas alterações nas taxas de corrosão e, conseqüentemente, nas geometrias resultantes no corpo de silício. Com a caracterização dessas mudanças comprovou-se suposições anteriores de que o efeito de compensação cinética encontrado na síntese direta de dimetilclorosilana (DMDCS) e silício, também ocorreria para a corrosão de silício em KOH, pois esses processos obedecem a lei de Arrhenius e tem um comportamento anisotrópico em silício. Os resultados obtidos, graças a um grande detalhamento de todos as etapas de processo e caracterização voltada à tecnologia do silício, comprovaram as suposições teóricas e mostraram como pode ser modificada a taxa de corrosão na anisotropia com a adição de metais em solução. / In the past few years it has been a huge evolution in industrial area of MEMS, and this one is characterized by the development of the processes of microelectronic to reduce cost and to integrate different systems that become very trustful in different applications. It is being done a work in silicon anisotropic etching in Potassium hydroxide (KOH) added with metallic impurities aiming the study of the kinetic compensation effect and the influence of these metals in the anisotropy and in etch rates. It was analyzed the effects of Zinc, Aluminum and Cupper and it could be observed changes in etch rates, and, consequently, in the resulting geometries. After characterization of theses changes it was proved that previous suppositions that the kinetic compensation effects found in direct synthesis of dimethyldichorosilane (DMDCS) and silicon would also occur for silicon anisotropic etching in KOH, due to both reactions follows Arrhenius law and are anisotropic reactions. The obtained results proved the theory suppositions that the etch rate and anisotropy can be modified when adding metals to the solution.

Thesis (M. Sc.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 92-101).

Thesis (MAppSci in Physiotheraphy) -- University of South Australia, 1994

Thesis (M.S.)--Central Connecticut State University, 1997. / Thesis advisor: Dr. Robert Trichka. " ... in partial fulfillment of the requirements for the degree of Master of Science in Physical Education." Includes bibliographical references (leaves 162-169).

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2007. / Title from title screen (site viewed July 9, 2007). PDF text: vii, 77 p. UMI publication number: AAT 3247183. Includes bibliographical references. Also available in microfilm and microfiche formats.

Nos últimos anos tem se dado uma evolução muito grande na área industrial de MEMS, e esta se caracteriza por desenvolvimento dos processos de microeletrônica para diminuição de custos e a própria integração de diferentes sistemas que passam a ser muito confiáveis em diferentes aplicações. Motivado pelas tendências de elevar os conhecimentos de processos para obtenção de MEMS, foi proposto um trabalho de corrosão anisotrópica de silício utilizando solução de hidróxido de potássio (KOH) junto com a adição de sais metálicos. O objetivo é comprovar o efeito de compensação cinética da reação e a influência destes metais no caráter anisotrópico e nas taxas de corrosão. Foi analisado o efeito de zinco, alumínio e cobre, e puderam ser observadas alterações nas taxas de corrosão e, conseqüentemente, nas geometrias resultantes no corpo de silício. Com a caracterização dessas mudanças comprovou-se suposições anteriores de que o efeito de compensação cinética encontrado na síntese direta de dimetilclorosilana (DMDCS) e silício, também ocorreria para a corrosão de silício em KOH, pois esses processos obedecem a lei de Arrhenius e tem um comportamento anisotrópico em silício. Os resultados obtidos, graças a um grande detalhamento de todos as etapas de processo e caracterização voltada à tecnologia do silício, comprovaram as suposições teóricas e mostraram como pode ser modificada a taxa de corrosão na anisotropia com a adição de metais em solução. / In the past few years it has been a huge evolution in industrial area of MEMS, and this one is characterized by the development of the processes of microelectronic to reduce cost and to integrate different systems that become very trustful in different applications. It is being done a work in silicon anisotropic etching in Potassium hydroxide (KOH) added with metallic impurities aiming the study of the kinetic compensation effect and the influence of these metals in the anisotropy and in etch rates. It was analyzed the effects of Zinc, Aluminum and Cupper and it could be observed changes in etch rates, and, consequently, in the resulting geometries. After characterization of theses changes it was proved that previous suppositions that the kinetic compensation effects found in direct synthesis of dimethyldichorosilane (DMDCS) and silicon would also occur for silicon anisotropic etching in KOH, due to both reactions follows Arrhenius law and are anisotropic reactions. The obtained results proved the theory suppositions that the etch rate and anisotropy can be modified when adding metals to the solution.

Stirring tanks are very important equipments used for mixing, separating, chemical reaction, etc. A typical stirring tank is a cylindrical vessel with an agitator driving the fluid and generating turbulence to promote mixing. Flotation cells are widely used stirring tanks in phase separation where multiphase flow is involved. Flotation refers to the process in which air bubbles selectively pick up hydrophobic particles and separate them from hydrophilic solids. This technology is used throughout the mining industry as well as the chemical and petroleum industries. In this research, efforts were made to investigate the multi-phase flow hydrodynamic problems of some flotation cells at different geometrical scales. Pitot-static and five-hope probes were employed to lab- pilot- and commercial-scale tanks for velocity measurements. It was found that the tanks with different scales have similar flow patterns over a range of Reynolds numbers. Based on the velocity measurement results, flotation tanks' performance was evaluated by checking the active volume in the bulk. A fast-response five-hole probe was designed and fabricated to study the turbulence characteristics in flotation cells under single- and multi-phase flow conditions. The jet stream in the rotor-stator domain has much higher turbulence intensity compared with other locations. The turbulent dissipation rate (TDR) in the rotor-stator domain is around 20 times higher than that near tank's wall. The TDR could be used to calculate the bubble and particle slip velocities. An isokinetic sampling probe system was developed to obtain true samples inthe multi-phase flow and then measure the local void fraction. It was found that the air bubbles are carried out by the stream and dispersed to the whole bulk. However, some of the bubbles accumulate in the inactive regions, where higher void fractions were detected. The isokinetic sampling probe was then extended to be an isokinetic borescope system, which was used to detect the bubble-particle aggregates in the tank. Aggregates were found in the high-turbulence level zones. The isokinetic sampling probe and the isokinetic borescope provide new methods for flotation tank tests. An experiment was also set up to study the dynamics of bubble particle impact. Four different modes were found for the collision. The criterion is that if the fluid drainage time is less than the residence time, the attachment will occur, otherwise, the particle will bounce back. / Ph. D.

Muscle weakness is one of the major causes of post-stroke disability. Stroke rehabilitation programs now often incorporate the same type of resistance training that is used for healthy subjects; however, the training effects induced from these training strategies are often limited for stroke patients. An important resistance training principle is that an optimal level of stress is exerted on the neuromuscular system, both during concentric (shortening) and eccentric (lengthening) contractions. One potential problem for post-stroke patients might be difficulties achieving sufficient levels of stress on the neuromuscular system. This problem may be associated with altered muscular function after stroke. In healthy subjects, maximum strength during eccentric contractions is higher than during concentric contractions. In individuals with stroke, this difference in strength is often increased. Moreover, it has also been shown that individuals with stroke exhibit alteration with respect to how the strength varies throughout the range of motion. For example, healthy subjects exhibit a joint specific torque-angle relationship that normally is the same irrespective of contraction mode and contraction velocity. In contrast, individuals with stroke exhibit an overall change of the torque-angle relationship. This change, as described in the literature, consists of a more pronounced strength loss at short muscle length. In individuals with stroke, torque-angle relationships are only partially investigated and so far these relationships have not been analysed using testing protocols that include eccentric, isometric, and concentric modes of contraction.   This thesis investigates the torque-angle relationship of elbow flexors in subjects with stroke during all three modes of contractions – isometric, concentric, and eccentric ­– and the relative loading throughout the range of movement during a resistance exercise. In addition, this thesis studies possible central nervous system mechanisms involved in the control of muscle activation during eccentric and concentric contractions.   The torque-angle relationship during maximum voluntary elbow flexion was examined in stroke subjects (n=11), age-matched healthy subjects (n=11), and young subjects (n=11) during different contraction modes and velocities. In stroke subjects, maximum torque as well as the torque angle relationship was better preserved during eccentric contractions compared to concentric contractions. Furthermore, the relative loading during a resistance exercise at an intensity of 10RM (repetition maximum) was examined. Relative loading throughout the concentric phase of the resistance exercise, expressed as percentage of concentric torque, was found to be similar in all groups. However, relative loading during the eccentric contraction phase, expressed as the percentage of eccentric isokinetic torque, was significantly lower for the stroke group. In addition, when related to isometric maximum voluntary contraction, the loading for the stroke group was significantly lower than for the control groups during both the concentric and eccentric contraction phases. Functional magnetic resonance imaging was used to examine differences between recruited brain regions during the concentric and the eccentric phase of imagined maximum resistance exercise of the elbow flexors (motor imagery) in young healthy subjects (n=18) and in a selected sample of individuals with stroke (n=4). The motor and premotor cortex was less activated during imagined maximum eccentric contractions compared to imagined maximum concentric contraction of elbow flexors. Moreover, BA44 in the ventrolateral prefrontal cortex, a brain area that has been shown to be involved in inhibitory control of motor activity, was additionally recruited during eccentric compared to concentric conditions. This pattern was evident only on the contralesional (the intact hemisphere) in some of the stroke subjects. On the ipsilesional hemisphere, the recruitment in ventrolateral prefrontal cortex was similar for both modes of contractions.    Compared to healthy subjects, the stroke subjects exhibited altered muscular function comprising a specific reduction of torque producing capacity and deviant torque-angle relationship during concentric contractions. Therefore, the relative training load during the resistance exercise at a training intensity of 10RM was lower for subjects with stroke. Furthermore, neuroimaging data indicates that the ventrolateral prefrontal cortex may be involved in a mechanism that modulates cortical motor drive differently depending on mode of the contractions. This might partly be responsible for why it is impossible to fully activate a muscle during eccentric contractions. Moreover, among individuals with stroke, a disturbance of this system could also lie behind the lack of contraction mode-specific modulation of muscle activation that has been found in this population. The altered neuromuscular function evident after a stroke means that stroke victims may find it difficult to supply a sufficient level of stress during traditional resistance exercises to promote adaptation by the neuromuscular system. This insufficiency may partially explain why the increase in strength, in response to conventional resistance training, often has been found to be low among subjects with stroke. / Muskelsvaghet är en av orsakerna till funktionshinder efter stroke. I rehabiliteringsprogram för personer som drabbats av stroke förekommer det numera att styrketräning används i syfte att öka muskelstyrkan. Effekten av styrketräning har dock ofta visat sig vara begränsad. En viktig styrketräningsprincip är att muskulaturen belastas tillräckligt nära maximal styrka under både koncentriska kontraktioner (när man lyfter en vikt) och excentriska kontraktioner (när man kontrollerat sänker en vikt). Ett potentiellt problem skulle kunna vara att personer med stroke inte belastas optimalt under träning på grund av förändrad muskelfunktion. Efter stroke är muskelfunktionen ofta förändrad såtillvida att styrkenedsättningen är mer uttalad under koncentriska kontraktioner. Därutöver har man funnit att styrkenedsättningen är mest uttalad när muskeln är i sitt mest förkortade läge. Detta fenomen har dock inte studerats för alla tre kontraktionstyper, det vill säga excentriska, koncentriska och isometriska kontraktioner, hos personer med stroke.   Denna avhandling undersöker sambandet mellan styrka och ledvinkel över armbågsleden hos personer med stroke under alla tre kontraktionstyper – excentrisk, koncentrisk och isometrisk, samt relativ belastning genom rörelsebanan under en styrketräningsövning. Därutöver undersöker denna avhandling också hjärnans aktiveringsmönster under excentriska och koncentriska kontraktioner.   Sambandet mellan styrka och ledvinkel undersöktes hos personer med stroke (n = 11), åldersmatchade (n = 11) och unga försökspersoner (n = 11). Jämfört med kontrollgrupperna var maximal styrka för personer med stroke mest nedsatt, samt även den oproportionerligt stora styrkenedsättningen vid kort muskelängd som mest uttalad, under koncentriska kontraktioner. Denna avvikelse var minst uttalad vid excentriska kontraktioner. Vidare studerades hur hög belastningen på muskulaturen var i jämförelse med muskelns maximala styrka under en styrketräningsliknande övning för armbågsflexorer vid en träningsintensitet på 10RM. Den uppmätta belastningen under den koncentriska fasen av styrketräningsövningen, uttryckt som procent av den genomsnittliga koncentriska styrkan, var densamma för alla grupperna. Under den excentriska fasen av övningen var dock belastningen, uttryckt som procent av den maximala excentriska styrkan, signifikant lägre för personer med stroke. Träningsbelastningen utgjorde också en lägre andel av den maximala isometriska styrkan för personer med stroke, både under den koncentriska och under den excentriska fasen.   Funktionell magnetresonanstomografi (fMRI) användes för att undersöka hjärnans aktiveringsmönster hos unga försökspersoner (n = 18) och hos individer med stroke (n = 4) när de föreställde sig att de utförde maximal styrketräning för armbågsflexorer (motor imagery). Resultatet visade att primära motorbarken och premotoriska barken var mindre aktiverade när unga friska försökspersonerna föreställde sig utföra maximala excentriska, jämfört med maximala koncentriska kontraktioner. Dessutom var en region i ventrolaterala prefrontala barken, som i tidigare studier visat sig vara inblandat i reglering och hämning av muskelaktivering, mer aktiverade under föreställda excentriska kontraktioner. Detta aktiveringsmönster i den prefrontala barken återfanns dock endast i den icke skadade hjärnhalvan hos personer med stroke.   Jämfört med kontrollgrupperna uppvisade försökspersonerna med stroke en förändrad muskelfunktion som bestod av en specifik nedsättning av styrkan under koncentriska kontraktioner samt också ett mer avvikande samband mellan styrka och ledvinkel under koncentriska kontraktioner. Den relativa belastningen under utförandet av en styrketräningsövning med en intensitet på 10RM var på grund av dessa avvikelser lägre för försökspersoner med stroke. Hjärnavbildnings-studierna indikerade att ventrolaterala prefrontala barken verkar vara involverat i ett kortikalt moduleringssystem som reglerar muskel-aktivering olika beroende på kontraktionstyp under maximala kontraktioner. Detta skulle kunna vara en underliggande mekanism bakom den hittills obesvarade frågan varför det är omöjligt att aktivera muskulaturen maximalt under excentriska kontraktioner. En störning av detta moduleringssystem hos personer med stroke verkar också kunna ligga bakom den förändrade regleringen av muskelaktivering som visat sig förekomma hos personer med stroke. Neuromuskulär funktion efter stroke är förändrad i flera avseenden vilket verkar medföra att muskulaturen inte belastas optimalt under konventionell styrketräning. Detta kan vara en delförklaring till varför styrkeökningen som svar på träning ofta är liten hos personer med stroke.

Cricket has evolved from a traditional and conservative sport to a fast-paced, vigorous game. As a result of this the physical conditioning programmes of players have changed drastically with regular fitness tests that are now an integral part of these programmes. In spite of this, no studies have made an attempt to determine the exact relationship between the physical and motor ability parameters of batsmen and their performance. The purpose of this study was, therefore, firstly to determine which physical and motor ability parameters discriminate between successful and less successful provincial academy batsmen and secondly, to determine how much these parameters contribute to the batting performance of provincial academy batsmen. Twenty-two batsmen from the Gauteng and North-West cricket academies in South Africa were used in this study. Thirteen batsmen (20.15 +- 1.41 years) participated during the 2004 season whilst nine batsmen (21.11 +- 1.83 years) took part during the 2005 season. The players were subjected to 23 physical and motor ability tests, whilst 72 isokinetic measurements were also taken. The data was analysed by means of descriptive statistics, cluster analyses, forward stepwise discriminant analyses and finally forward stepwise multiple regression analyses. The discriminant analyses showed that right (RKEPT) and left knee extensor peak torque (LKEPT), right knee extensor average power (RKEAP), left knee extensor total work (LKETW) and left knee flexor peak torque (LKFPT) (all at 30°/sec), as well as LKEPT, RKEPT and L.KEAP (all at 24O°/sec ), left (LIRAP) and right shoulder internal rotator average power (RIRAP). right shoulder external/internal rotator peak torque ratio (REIRPTR) and right shoulder internal rotator peak torque (RIRPTJ (all at 24O°/sec) as well as left shoulder internal rotator total work (LIRTW) (60°/sec) discriminated non-significantly between the successfu1 (top 5 ranked batsmen of both seasons) and less successful academy batsmen. The physical and motor ability parameters which were identified as discriminators were left 505 agility, shuttle run aerobic endurance and IRM (repetition-maximum) hack squat strength (all significant) (p 5<= 0.05) whilst left grip strength and abdominal muscle strength discriminated non-significantly. The forward stepwise multiple regression analyses indicated that RKEPT 30' (16%). LKEPT 30' (7%), RKEAP 30' (7%), LKFPT 30' (7%), LKEAP 240" (6%), RKFPT 240" (5%). LKETW 30" (5%) and LKEPT240° (4%) were the isokinetic knee strength parameters which contributed non-significantly to batting performance. The isokinetic shoulder strength parameters which also contributed non-significantly to batting performance were: RIRPT240° (28%). LIRAP 240' (16%), REZRPTR 240' (8%). LIRTW 60° (5%) and RIRAP 240' (4%). Vertical jumping power (13%) (p 50.05), left 505 agility (9%) (p 50.05), abdominal muscle strength (5%) (p 50.05), aerobic capacity (10%). IRM bench press strength (7%), IRM hack squat strength as well as left shoulder internal rotation flexibility (4% each) were the physical and motor ability parameters which contributed to batting performance. The conclusion that can, therefore, be drawn is that physical and motor ability parameters contribute to the performance of provincial academy batsmen and that these components should be included in the physical conditioning programmes of batsmen / Thesis (M.Sc. (Human Movement Science))--North-West University, Potchefstroom Campus, 2007.