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Adolescent growth provides a unique opportunity for the growing body to adapt to external stimuli. A positive association between site-specific mechanical loading and increases in regional bone mineral content (BMC) during adolescence is established. Mechanical loads associated with middle-distance running expose the skeleton to a combination of compressive ground reaction forces and muscular contraction. Previous studies concerning musculoskeletal health in active adolescents are largely limited to planar, two-dimensional measures of bone mineral status, using Dual X-ray Absorptiometry (DXA). Intrinsic bone material properties are accurately measured using DXA. However, the interaction between bone material and structural properties that reflects the mechanical integrity of bone require a combination of imaging modalities. Magnetic Resonance Imaging (MRI) provides a three-dimensional geometric and biomechanical assessment of bone. When MRI is integrated with DXA technology, an effective non-invasive method of assessing in vivo bone strength is achieved. The impact of high training volumes on musculoskeletal development of male and female adolescent athletes engaged in repetitive, high magnitude mechanical loading has not been investigated. Specifically, differences in total body and regional bone mineral, bone and muscle geometry, bone biomechanical indices and bone strength at differentially-loaded skeletal sites have not been compared between adolescent middle-distance runners and age- and gender-matched non-athletic controls. Objectives: (i) to investigate the effects of intense sports participation involving mechanical loading patterns on bone mineral, bone and muscle geometry, biomechanical indices and estimated regional bone strength between elite adolescent male and female middle-distance runners and age- and gender-matched controls (ii) to examine factors predictive of total body BMC, distal tibial bone geometry, distal tibial bone strength, and Hip Strength Analysis (HSA)- derived indicators of bone strength at the femoral neck. Methods: Four groups of 20 adolescents were comprised of male (mean (SD) age 16.8 ± 0.6 yr, physical activity 14.1 ± 5.7 hr.wk-1) and female (age 16 ± 1.7 yr, physical activity 8.9 ± 2.1 hr.wk-1) middle-distance runners, and male (16.4 ± 0.7 yr, physical activity 2.2 ± 0.7 hr.wk-1) and female (age 16 ± 1.8 yr, physical activity 2.0 ± 0.07 hr.wk-1) controls. Total body and regional BMC were calculated using DXA. Distal tibial bone and muscle cross-sectional areas (CSA) were assessed using MRI. To calculate distal tibial bone strength index (BSI), a region of interest representing 10% of the mid distal tibia was analysed for DXA-derived bone mineral and was combined with bone geometry and biomechanical properties from MRI assessments. Calculations for femoral neck strength were acquired from DXA-derived HSA software. Results: No differences were found between male athletes and controls for unadjusted BMC at total body or regional sites. After covarying for fat mass (kg), male athletes displayed greater BMC at the lumbar spine (p = 0.001), dominant proximal femur (p = 0.001) and dominant leg (p = 0.03) than male controls. No differences were found in distal tibial bone geometry, bone strength at the distal tibia or HSA-derived indicators of bone strength at the femoral neck between male athletes and controls. Lean tissue mass and fat mass were the strongest predictors of total body BMC (R2 = 0.71), total muscle CSA explained 43.5% of variance in BSI at the distal tibia, and femur length and neck of femur CSA explained 33.4% of variance at the femoral neck. In females, athletes displayed greater unadjusted BMC at the proximal femur (+3.9 ±1.4 g, p = 0.01), dominant femoral neck (+0.5 ± 0.12 g, p = 0.01) and dominant tibia (+4.1 ± 2.1 g, p = 0.05) than female controls. After covarying for fat mass (kg), female athletes displayed greater (p = 0.001) total body, dominant proximal femur and dominant leg BMC than female controls. Female athletes also showed greater distal tibial cortical CSA (+30.9 ± 9.5 mm2, p = 0.003), total muscle (+240.2 ± 86.4 mm2, p = 0.03) and extensor muscle (+46.9 ±19.5 mm2, p = 0.02) CSA, smaller medullary cavity (-32.3 ± 14.7 mm2, p = 0.03) CSA and greater BSI at the distal tibia (+28037 ± 8214.7 g/cm3.mm4, p = 0.002) than female controls. Lean tissue mass and fat mass were the strongest predictors of total body BMC (R2 = 65), hours of physical weekly activity and total muscle CSA explained 58.3% of the variance of distal tibial BSI, and neck of femur CSA accounted for 64.6% of the variance in a marker of femoral neck HSA. Conclusion: High training loads are associated with positive musculoskeletal outcomes in adolescent middle-distance runners compared to non-athletic controls. Exposure to similar high training loads may advantage female adolescent athletes, more than male adolescent athletes compared with less active peers in bone strength at the distal tibia.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: Stuart A. Binder-Macleod, Dept. of Physical Therapy. Includes bibliographical references.

The goal of this research work was to introduce the whole process of developing and validating a 3D lower extremity musculoskeletal model and to test the ability of the model to predict the muscles recruitment of the different muscles involved in human locomotion as well as determining the corresponding forces and moments generated around the different joints in the lower extremity. Therefore the model can be applied in one of the important fields of orthopaedics which is joint replacement; the case study used in such application is the total knee replacement. The knee reaction forces were compared to the pattern obtained by Harrington (1992), where the hip moment components (Flexion/extension, internal/external, and abduction/adduction) were all compared to the patterns obtained from the Hip98 data base. It was shown in the different graphs of joints forces and moments that the model was able to produce very close results when comparing pattern and magnitude to the literature data. Thus, this 3D biomechanical model is sophisticated enough to be used for surgery evaluation such as in total knee replacement, where the damaged cartilage and bone are removed from the surface of the knee joint and replaced with a man-made. The case study of the second part of the research work presented involved the comparison of the gait pattern between two main knee joint types, Metallic and Allograft knee joints against normal subjects (Control group). A total of fifteen subjects participated in this study, five subjects in each group. It was concluded that based on the study conducted and the statistical evidence obtained that the introduced model can be used for applications that involves joint surgeries such as knee replacement that ultimately can be utilized in surgery evaluation.

Thesis (M.S.)--University of Delaware, 2006. / Principal faculty advisor: Stuart A. Binder-Macleod, Dept. of Physical Therapy. Includes bibliographical references.

Thesis (M.S.)--University of Delaware, 2006. / Principal faculty advisors: Robert E. Akins, Jr. and Deni S. Galileo, Dept. of Biological Sciences. Includes bibliographical references.

Thesis (M.Sc.)--York University, 2004. Graduate Programme in Kinesiology and Health Science. / Typescript. Includes bibliographical references (leaves 61-64). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL:http://gateway.proquest.com/openurl?url%5Fver=Z39.88-2004&res%5Fdat=xri:pqdiss&rft%5Fval%5Ffmt=info:ofi/fmt:kev:mtx:dissertation&rft%5Fdat=xri:pqdiss:MQ99385

Thesis (M.S.M.E.)--University of Delaware, 2009. / Principal faculty advisor: Jill S. Higginson, Dept. of Mechanical Engineering. Includes bibliographical references.