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Title: Computational modeling and mechanical analysis of compression sportswear
Authors: Lin, Yinglei
Degree: Ph.D.
Issue Date: 2011
Abstract: Compression garments such as compression sportswear (CS), tights and stockings can potentially enhance athletic performance and prevent injuries during running. Wearing CS, particularly compression tights, can increase venous blood flow, and improve lower limb muscle pumping action by helping to remove blood lactate from the exercising muscles. Direct experimental techniques, such as use of force sensors were developed and applied to investigate the biomechanical interactions between the human lower limb and the garment. However, the direct biomechanical measurement of the contact pressure between the body and garment is costly and time consuming. In addition, direct measurement of compression effects such as internal stress and strain is difficult. Computational methods provide an alternative approach for studying the compression exerted by CS on the human body. In clinical practice, Laplace's law is widely used to calculate the contact pressure exerted by compression stockings on patients. However, only the elasticity of the fabric materials and the global curvature of the human lower limb are considered in Laplace's law. Laplace's pressure has been used to calculate the local pressure on the transverse sections of the lower limb. However, calculation of the local curvature is complicated and considers only the two-dimensional geometry of the lower limb. Laplace's law cannot be used to calculate the internal stress and strain of the human body or clothing deformation. Accordingly, our understanding and ability to quantify CS design from a biomechanical perspective is still far from complete. In this study, a series of comprehensive finite element (FE) models of a male lower limb and CS in both standing and knee flexion postures were developed. The models used commercially available three-dimensional anatomic lower limb geometry models and incorporated nonlinear material properties, large deformations, and friction conditions. The results of the computation model were validated by comparisons between pressure distributions, clothing deformations and Laplace's law calculations. In general, the FE predictions were in good agreement with experimental measurements and theoretical calculations. For the parametric study of factors including fabric elasticity, density, thickness and extension, a statistics-based FE model utilizing a fabric tube and cylinder supporter was developed. The contact pressures predicted using the FE model were consistent with results measured with differently knitted fabrics. An increasing trend in the predicted contact pressure was noted to be in line with the increases in all the different factors. From the FE model predictions, the nonlinear elastic material properties (i.e., hyperelastic coefficients μ and α) and shape dimensions (i.e., thickness and strain) of the fabric tube were found to be important design factors influencing contact pressure. Other design factors such as fabric density and interface friction coefficient play less important roles in normal contact pressure. The optimal FE model can be obtained using the response surface method (RSM) analysis. Both the measured and predicted pressures indicate that the knitted fabric tube can exert the designated lightweight pressure on the cylinder supporter.
To investigate the contact pressure exerted by CS on athletes, experimental measurements were performed on trained runners wearing custom-made CS with extensions similar to those in the FE model for different sections (i.e., the ankle, calf, knee, mid-thigh, and upper-thigh). Measurements were made at important muscle points in both standing and flexion postures. The results show that contact pressure generally graduates from the calf to the thigh in all postures. The contact pressure at different sides of the same muscle tended to be very similar to each other as the knee flexion angle increased, including the gastrocnemius medialis (GM) and gastrocnemius lateralis (GL), and vastus medialis (VM) and vastus lateralis (VL). In the standing FE model, the contact pressures at the posterior of the ankle, anterior of the calf, patella, GM, GL, and VL were relatively large. The clothing deformation distribution was smoother in contrast to the corresponding contact pressure distribution along the length of the leg. This may be because the clothing deformation is mainly influenced by the global curvature of the human leg geometry and the fabric material of the clothing; meanwhile, the large variations in the contact pressure may be caused by the local curvature of the small regions of the human leg geometry as well as and the fundamental anatomic bony and muscular structures. In the flexion FE model, a complicated FE model of the lower limbCS model at 30° knee flexion was developed. The maximum contact pressure was found at the posterior of the ankle, while the maximum and minimum clothing deformations were found at the anterior and posterior parts of the knee, respectively. The peak contact pressure at different sections including the ankle, calf, and knee, increased in the flexion model. Although the clothing deformation substantially increased over a large region at the anterior part of the knee in the flexion model, the corresponding contact pressure was similar to that in the standing position. These results may be because of the similarity of the anatomic curvature at this region in both the 30° flexion and standing positions. Using the FE method, manufacturers can develop CS products that will exert specified pressures on the human body over specific regions in specific postures.
Subjects: Sport clothes.
Sport clothes -- Technological innovations
Finite element method.
Hong Kong Polytechnic University -- Dissertations
Pages: xxiii, 157 leaves : ill. (some col.) ; 30 cm.
Appears in Collections:Thesis

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