Hypertonia is seen in 85% of people with Multiple Sclerosis (pwMS) resulting in disability and functional restrictions. Hypertonia can be caused by increases in passive stiffness and enhanced stretch reflexes (spasticity) and is frequently managed clinically using passive stretches. However, the optimal parameters of stretching such as the applied torque and stretch duration remain unclear. During commonly prescribed ankle plantarflexor stretches pwMS produced higher torques when standing in a weight bearing position compared to stretches applied using the upper limbs. Stretches could be held for 120 seconds on average and stretch duration was mainly limited by fatigue. People with higher disability tended to favour more supported stretching positions. The effects of stretching for either 30 or 10 minutes using a customised motor at three torque levels covering the range that MS participants could produce was investigated. Compared to the 10 minute stretch, greater reductions in passive stiffness and greater increases in range of movement (ROM) were seen immediately following the 30 minute stretch with the effects being sustained for the 30 minute post stretch period. Higher levels of applied torque resulted in a greater change in ROM however; there was no effect of applied torque on passive stiffness. Stretch reflex mediated stiffness was unaffected by the stretching intervention and showed transient post stretch increases. Ultrasonography was used to investigate changes in muscle–tendon length and strain in pwMS and controls and following stretching. PwMS showed evidence of stiffer muscles and increased tendon length at baseline compared to controls. Following a 10 minute stretch overall muscle length did not increase in pwMS, although increases in strain in the musculotendinous junction region were observed suggesting that more proximal regions of the muscle was likely to have contributed significantly to overall stiffness. This work highlights that stretch duration and levels of applied torque are critical factors in determining the effectiveness of stretches. The pathological mechanisms underlying hypertonia at a molecular and structural level and the effects of stretching on components of the musculo-tendinous structure and on functional ability should be ascertained.

Heart failure is an important medical disease and impacts millions of people throughout the world. In order to treat this problem, biomaterial injectable treatment injected into the myocardium of the failing LV are currently being developed. Through this treatment, the biomaterial material injections can reduce wall stresses during the cardiac remodeling process. By using computational techniques to analyze the effects of a treatment involving the injection of biomaterial material into the LV after MI, the material parameters of the hydrogel injections can be optimized. The results shows that the hydrogel injections could reduce the global average fiber stress and the transmural average stress seen from optimization. These results indicated that the hydrogel injections could influence the stiffness in passive LV tissue, but there is still need for more research on the active part of ventricular contraction. Conclusion: hydrogel injection is a viable way to alter ventricular mechanical properties.

ix Flexibility has traditionally been considered an important component of human physical fitness but this conjecture lacks supporting empirical evidence. While there is extensive published research examining the relative importance of flexibility and the impact of various methods of stretching on levels of flexibility, performance and injury risk, the quality of studies has varied considerably, reliability and validity of methodology has not always been proven, and rationale has at times been questionable. Additionally, much literature has focused on static flexibility which is not necessarily related to properties of the musculotendinous unit and thus dynamic flexibility. This thesis was designed to fill gaps in the existing literature by using accepted methods to establish relative and absolute reliability of hamstring flexibility tests, consider the comparability of static and dynamic components of the global concept of flexibility and explore how dynamic flexibility and performance are influenced by fatiguing exercise and subsequent static stretching. The first aim was realised by a repeated measures study designed to establish the intraday and interday, intrarater reliability and measurement error of static and dynamic measures of hamstring flexibility. Significant relative reliability for measures of static and dynamic hamstring flexibility was demonstrated via intraclass correlation coefficient (3,1) but limits of agreement analysis indicated there was a degree of absolute measurement error that must be interpreted in relation to analytical goals. The second aim required evaluation of relationships shared by static and dynamic measures of hamstring flexibility. Significant relationships between the different static flexibility tests were established but the extent of unexplained variance indicated that only measurements from the same tests should be directly compared to each other. Relationships between different measures of dynamic flexibility and static flexibility varied from non-significant to moderately strong, suggesting that measures of static and dynamic flexibility are not identical and results should not be interchanged between the two types of tests. Due to a lack of explanatory empirical evidence, the final chapter aimed via a prospective randomised repeated measures study to investigate the impact of fatigue and post-exercise static stretching on measures of dynamic flexibility and performance. Fatigue resulted in no significant changes to passive or active dynamic flexibility measures but a significant worsening of static flexibility levels and perceived stiffness. Post-exercise stretch resulted in significantly increased passive and active energy absorption immediately and 18 hours post-exercise and in significantly reduced joint position sense immediately post-exercise. Effect sizes were small so the clinical meaningfulness of performing post-exercise static stretching is questionable, particularly if performed in place of other, potentially more beneficial practices. / Thesis (DPhil)--University of Pretoria, 2013. / gm2014 / Biokinetics, Sport and Leisure Sciences / unrestricted