Thesis (Ph. D.)--Ohio State University, 1982. / Includes bibliographical references (leaves 153-156). Available online via OhioLINK's ETD Center

Thesis--University of Michigan. / Includes bibliographical references.

Thesis--University of Michigan. / Includes bibliographical references.

No description available.

Minimal footwear sales have encountered rapid growth over the last several years. Minimal footwear are often constructed with thin basic uppers and thin, flexible midsoles. It is likely that running in minimal footwear will require adaptation and adjustments as the amount of cushioning and the geometry of the foot/ground interface will be substantially different than what many are accustomed to. This research investigated the effect footwear cushioning amount and the running surface had on running patterns. Study 1 (Chapter IV) utilized two different running footwear conditions and two different cushioned treadmill conditions, as well as a barefoot condition, to investigate the effect cushioning magnitude and mode had on running patterns. Subjects ran for six minutes at 3.0 m/s for each footwear/surface condition while kinematics and acceleration data were collected. Study 2 (Chapter V) utilized three footwear conditions as well as a barefoot condition to investigate the effect of running in minimal footwear for the first time. Subjects ran for six minutes at 3.0 m/s while wearing each of the four conditions on an aluminum belt treadmill while kinematic and acceleration data were collected. The three footwear conditions were very similar except for the amount of underfoot material (foam) which varied from very little in the most minimal condition to a typical training footwear amount in the thickest condition. Study 3 (Chapter VI) utilized the same three footwear conditions worn in study 2. Subjects ran for 30 minutes at 3.0 m/s wearing each of the three footwear conditions while kinematic and acceleration data were collected in order to investigate the response to minimal footwear over the course of a sustained run. Results of Study 1 suggest that the amount of underfoot cushioning as well as how that cushioning was applied (footwear vs. surface) were both important and affected adjustments made during the run. The foot was more horizontal, the ankle joint complex more plantar flexed, and the knee more flexed in the sagittal plane at TD when running barefoot compared to all other conditions. Peak acceleration values were reduced for the most cushioned condition compared to all others. The thigh segment was more vertical at TD and peak tibial internal rotation at midstance was reduced when footwear were worn. This indicated cushioning provided through footwear altered running patterns compared to cushioning provided through the surface. More investigation is necessary to fully understand all the factors involved, but our research showed that cushioning magnitude is not the only factor affecting running patterns when footwear or running surface is altered. Some Study 2 dependent variables indicated running patterns to be significantly different for both barefoot and very minimal footwear conditions compared to footwear with thicknesses more similar to typical training footwear. Other dependent variables showed barefoot to separate from all footwear conditions implying that unique strategies were utilized for barefoot running even when compared to minimal footwear providing very little cushioning or protection. Peak accelerations implied that cushioning limited the shock transferred to the tibia and the head. Most coordination measures implied barefoot running to be significantly more variable than running in minimal running shoes. Adaptations due to running in footwear with unknown cushioning characteristics occurred quickly, in as few as six to eight steps. Kinematic adjustments were also occurring later in the six minute run. Study 3 kinematic and acceleration dependent variables indicated adjustments were made to running patterns as a result of changes in the amount of underfoot material. The foot segment was less horizontal and the AJC more dorsiflexed for the thick condition compared to both others. These changes did not completely compensate for changes in underfoot material however, as peak accelerations at the tibia and the head were increased as underfoot material was reduced. Runners were found to adjust running patterns as the thirty minute run progressed regardless of footwear condition. Several kinematic dependent variables were found to significantly increase or decrease as the 30 minute run progressed. In summary, the amount of cushioning and the mode of cushioning were found to effect running patterns. Given these findings, it is not surprising adaptations were found when comparing running in minimal footwear to running in footwear with more typical midsole thicknesses. Cushioning magnitude and the geometry of the foot/ground interface were substantially different between these footwear conditions. Although the thin condition provided almost no cushioning, differences were still shown between barefoot and this condition. Barefoot running may require a unique solution even compared to running in extremely minimal footwear. When runners wore minimal running shoes for the first time, some adaptations occurred quickly; however, adjustments were still occurring much later into the six and 30 minute runs. Runners who purchase minimal footwear can expect changes in running patterns.

Thesis (Ph. D.)--Victoria University (Melbourne, Vic.), 2007. / Includes bibliographical references.

Footwear can affect postural stability in individuals, particularly in elderly people. Aging-related decline in postural stability, particularly in the mediolateral (ML) direction, is a risk factor for falls and fall-related injuries among older adults. This study aimed to investigate the effects of high cushioned and minimal shoes on dynamic postural stability in ML during obstacle crossing in defined older and younger adults. Six healthy older adults (50–60 years old, body weight: 74.8 kg, body height: 168.0 cm) and six healthy younger adults (18–32 years old, body weight: 73.8 kg, body height: 174.8 cm) participated in the study. A Vicon motion analysis system with 10 optical cameras was used to capture the obstacle (20 cm height) crossing motion of the participants at 200 Hz, and ground reaction forces of obstacle crossing were collected at 1000 Hz. Motion data of obstacle crossing were collected at three shoe conditions, namely, minimal shoe, high cushioned shoe and barefoot (control). Data from five trials of obstacle crossing for each shoe condition were processed using Vicon Nexus software 2.11.0 and Matlab R2013b. Displacement and velocity of centre of mass (COM) in the ML direction, COM–centre of pressure (COP) ML separation, step length, step velocity, toe clearance, pre-horizontal distance, hip flexion angle and hip abduction angle during obstacle crossing were examined. One-way ANOVA with pairwise analysis showed that toe clearance was significantly larger in the high cushioned shoe conditions than in the minimal shoe and barefoot conditions in older adults (high cushioned shoes vs. barefoot: p = 0.019; cushioned shoes vs. minimal shoes: p = 0.031) and younger adults (high cushioned shoes vs. barefoot: p = 0.016; high cushioned shoes vs. minimal shoes: p = 0.000). No significant difference in the measures was found between the minimal shoe and barefoot conditions in each group. Compared with older adults, younger adults showed significantly larger step length in barefoot condition (p = 0.000) and minimal shoe (p = 0.016). Independent t-test for examination of the significant difference of the means of each measure when the shoe condition was changed showed that only step length and step velocity were significantly different between older and younger adults. When the shoe condition was changed from minimal shoe or barefoot to high cushioned shoe, older adults showed significantly bigger change in step velocity (10.04 ± 4.39 cm/s for older; 1.87 ± 0.81 cm/s for younger; p = 0.034) and step length (14.26 ± 6.99 cm for older; 2.086 ± 1.13 cm for younger; p = 0.041) than younger adults. This result indicates that older adults had 23% greater total range of step length and 12% greater total range of step velocity compared with younger adults when shoe condition changed. Moreover, older adults showed 16% smaller total range in their maximal COM-COP ML separations than younger adults when shoe condition changed. It is concluded that high cushioned shoes can influence dynamic postural stability in the ML direction during obstacle crossing in younger and older adults. The minimal shoe and barefoot conditions did not show significant influence on postural stability in the ML direction during obstacle crossing in older and younger adults. The minimal shoe on dynamic postural stability in the ML direction is not significant. Age differences in dynamic postural stability in the ML direction during obstacle crossing were found at the same shoe conditions. Moreover, when shoe condition was changed, shoe cushioning conditions affected postural stability to a larger extent in older adults compared with younger adults. The high cushioned shoe led to a more challenged postural stability in adults aged 50 to 60 than younger adults aged 18 to 32.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Vita. / Includes bibliographical references. / by Ronald James Salig. / M.S.

In 2007 the production of expanded polystyrene (EPS) in the world was over 4 million tonnes and is expected to grow at 6 percent per year. With the increased concern about environmental protection, alternative biodegradable materials from renewable resources are of interest. The present doctoral thesis work successfully demonstrates that starch-based foams with mechanical properties similar to EPS can be obtained by reinforcing the cell-walls in the foams with cellulose nanofibers (MFC). High cellulose nanofiber content nanocomposites with a highly plasticized (50/50) glycerol-amylopectin starch matrix are successfully prepared by solvent-casting due to the high compatibility between starch and MFC. At 70 wt% MFC, the nanocomposites show a remarkable combination of high tensile strength, modulus and strain to failure, and consequently very high work to fracture. The interesting combination of properties are due to good dispersion of nanofibers, the MFC network, nanofiber and matrix properties and favorable nanofiber-matrix interaction. The moisture sorption kinetics (30% RH) in glycerol plasticized and pure amylopectin film reinforced with cellulose nanofibers must be modeled using a moisture concentration-dependent diffusivity in most cases. The presence of cellulose nanofibers has a strong reducing effect on the moisture diffusivity. The decrease in zero-concentration diffusivity with increasing nanofiber content could be due to geometrical impedance, strong starch-MFC molecular interaction and constrained swelling due to the cellulose nanofiber network present. Novel biomimetic starch-based nanocomposite foams with MFC contents up to 40 wt% are successfully prepared by freeze-drying. The hierarchically structured nanocomposite foams show significant increase in mechanical properties in compression compared to neat starch foam. Still, better control of the cell structure could further improve the mechanical properties. The effect of cell wall composition, freeze-drying temperature and freezing temperature on the resulting cell structure are therefore investigated. The freeze-drying temperature is critical in order to avoid cell structure collapse. By changing the starch content, the cell size, anisotropy ratio and ratio between open and closed cells can be altered. A decrease in freezing temperature decreases the cell size and increases the anisotropy ratio. Finally, mechanical properties obtained in compression for a 30 wt% MFC foam prepared by freeze-drying demonstrates comparable properties (Young's modulus and yield strength) to expanded polystyrene at 50% RH and similar relative density. This is due to the reinforcing cellulose nanofiber network within the cell walls. / QC 20100913

Ce travail de thèse étudie l'effet des caractéristiques spécifiques des semelles de chaussures de course à pied minimalistes sur le patron de course. La première partie de ce travail tente de déterminer les condition expérimentales idéales et préconise l'utilisation de la course sur piste plutôt que sur tapis ainsi qu'un temps de 5 à 7 minutes de course nécessaires à la stabilisation du patron de course lors d'une session de course en chaussures minimalistes. Contrairement à l'épaisseur globale de la semelle, l'augmentation du drop a une influence sur le patron de pose du pied augmentant la flexion dorsale et diminuant la force de réaction du sol à l'impact. Le port de chaussures minimalistes ne présenterait pas d'avantage d'un point de vue de la prévention des blessures. Les études futures devront se concentrer sur les évolutions à long terme du patron de course lors de l'utilisation de chaussures minimalistes. / This thesis work study the specific features of the minimalist shoe sole on running pattern. The first part of this work tried to determine ideal experimental conditions and preconize utilisation of overgound running rather than treadmill running. An adaptation duration of 5 to 7 minutes is also required to the running pattern stabilisation when running in minimalist shoes. Opposite to the sole thickness, increasing the drop affect de foot strike pattern increasing dorsiflexion and decreasing ground reaction force at impact. Running in minimalist shoe would not be advantageous concerning injury risk. Future studies should focus on the long-term evolution of the running pattern when using minimalist shoes.