The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Edward M Wojtys - One of the best experts on this subject based on the ideXlab platform.
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effect of increased quadriceps Tensile Stiffness on peak anterior cruciate ligament strain during a simulated pivot landing
Journal of Orthopaedic Research, 2014Co-Authors: David B Lipps, James A Ashtonmiller, Edward M WojtysAbstract:ACL injury prevention programs often involve strengthening the knee muscles. We posit that an unrecognized benefit of such training is the associated increase in the Tensile Stiffness of the hypertrophied muscle. We tested the hypothesis that an increased quadriceps Tensile Stiffness would reduce peak anteromedial bundle (AM-)ACL relative strain in female knees. Twelve female cadaver knees were subjected to compound impulsive two-times body weight loads in compression, flexion, and internal tibial torque beginning at 15° flexion. Knees were equipped with modifiable custom springs to represent the nonlinear rapid stretch behavior of a normal and increased Stiffness female quadriceps (i.e., 33% greater Stiffness). Peak AM-ACL relative strain was measured using an in situ transducer while muscle forces and tibiofemoral kinematics and kinetics were recorded. A 3D ADAMS™ dynamic biomechanical knee model was used in silico to interpret the experimental results which were analyzed using a repeated-measures Wilcoxon test. Female knees exhibited a 16% reduction in peak AM-ACL relative strain and 21% reduction in change in flexion when quadriceps Tensile Stiffness was increased by 33% (mean (SD) difference: 0.97% (0.65%), p = 0.003). We conclude that increased quadriceps Tensile Stiffness reduces peak ACL strain during a controlled study simulating a pivot landing.
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morphologic characteristics help explain the gender difference in peak anterior cruciate ligament strain during a simulated pivot landing
American Journal of Sports Medicine, 2012Co-Authors: David B Lipps, James A Ashtonmiller, Edward M WojtysAbstract:Background: Gender differences exist in anterior cruciate ligament (ACL) cross-sectional area and lateral tibial slope. Biomechanical principles suggest that the direction of these gender differences should induce larger peak ACL strains in females under dynamic loading.Hypothesis: Peak ACL relative strain during a simulated pivot landing is significantly greater in female ACLs than male ACLs.Study Design: Controlled laboratory study.Methods: Twenty cadaveric knees from height- and weight-matched male and female cadavers were subjected to impulsive 3-dimensional test loads of 2 times body weight in compression, flexion, and internal tibial torque starting at 15° of flexion. Load cells measured the 3-dimensional forces and moments applied to the knee, and forces in the pretensioned quadriceps, hamstring, and gastrocnemius muscle equivalents. A novel, gender-specific, nonlinear spring simulated short-range and longer range quadriceps muscle Tensile Stiffness. Peak relative strain in the anteromedial bundle ...
Tamalkhani Syammaun - One of the best experts on this subject based on the ideXlab platform.
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dynamic properties of stone mastic asphalt mixtures containing waste plastic bottles
Construction and Building Materials, 2012Co-Authors: Taher Baghaee Moghaddam, Mohamed Rehan Karim, Tamalkhani SyammaunAbstract:Abstract Fatigue failure is a common problem of asphaltic concrete which can lead to pavement damage. Many studies have been conducted to find ways for increasing fatigue life of asphalt concrete mixtures. This study investigates effects of adding waste polyethylene terephthalate (PET) on Stiffness and fatigue properties of SMA mixtures at optimum asphalt contents. Different percentages of waste PET with maximum size of 2.36 mm were added to SMA mixtures. Indirect Tensile Stiffness modulus test and indirect Tensile fatigue test were conducted at temperature of 20 °C and at three different stress levels (250, 350, 450 kPa). The results showed that Stiffness modulus of mixture increased at lower amount of PET content; however, adding higher amount of PET made mixture less stiff. In addition, PET reinforced mixtures exhibit significantly higher fatigue lives compared to the mixtures without PET.
David B Lipps - One of the best experts on this subject based on the ideXlab platform.
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effect of increased quadriceps Tensile Stiffness on peak anterior cruciate ligament strain during a simulated pivot landing
Journal of Orthopaedic Research, 2014Co-Authors: David B Lipps, James A Ashtonmiller, Edward M WojtysAbstract:ACL injury prevention programs often involve strengthening the knee muscles. We posit that an unrecognized benefit of such training is the associated increase in the Tensile Stiffness of the hypertrophied muscle. We tested the hypothesis that an increased quadriceps Tensile Stiffness would reduce peak anteromedial bundle (AM-)ACL relative strain in female knees. Twelve female cadaver knees were subjected to compound impulsive two-times body weight loads in compression, flexion, and internal tibial torque beginning at 15° flexion. Knees were equipped with modifiable custom springs to represent the nonlinear rapid stretch behavior of a normal and increased Stiffness female quadriceps (i.e., 33% greater Stiffness). Peak AM-ACL relative strain was measured using an in situ transducer while muscle forces and tibiofemoral kinematics and kinetics were recorded. A 3D ADAMS™ dynamic biomechanical knee model was used in silico to interpret the experimental results which were analyzed using a repeated-measures Wilcoxon test. Female knees exhibited a 16% reduction in peak AM-ACL relative strain and 21% reduction in change in flexion when quadriceps Tensile Stiffness was increased by 33% (mean (SD) difference: 0.97% (0.65%), p = 0.003). We conclude that increased quadriceps Tensile Stiffness reduces peak ACL strain during a controlled study simulating a pivot landing.
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morphologic characteristics help explain the gender difference in peak anterior cruciate ligament strain during a simulated pivot landing
American Journal of Sports Medicine, 2012Co-Authors: David B Lipps, James A Ashtonmiller, Edward M WojtysAbstract:Background: Gender differences exist in anterior cruciate ligament (ACL) cross-sectional area and lateral tibial slope. Biomechanical principles suggest that the direction of these gender differences should induce larger peak ACL strains in females under dynamic loading.Hypothesis: Peak ACL relative strain during a simulated pivot landing is significantly greater in female ACLs than male ACLs.Study Design: Controlled laboratory study.Methods: Twenty cadaveric knees from height- and weight-matched male and female cadavers were subjected to impulsive 3-dimensional test loads of 2 times body weight in compression, flexion, and internal tibial torque starting at 15° of flexion. Load cells measured the 3-dimensional forces and moments applied to the knee, and forces in the pretensioned quadriceps, hamstring, and gastrocnemius muscle equivalents. A novel, gender-specific, nonlinear spring simulated short-range and longer range quadriceps muscle Tensile Stiffness. Peak relative strain in the anteromedial bundle ...
James A Ashtonmiller - One of the best experts on this subject based on the ideXlab platform.
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effect of increased quadriceps Tensile Stiffness on peak anterior cruciate ligament strain during a simulated pivot landing
Journal of Orthopaedic Research, 2014Co-Authors: David B Lipps, James A Ashtonmiller, Edward M WojtysAbstract:ACL injury prevention programs often involve strengthening the knee muscles. We posit that an unrecognized benefit of such training is the associated increase in the Tensile Stiffness of the hypertrophied muscle. We tested the hypothesis that an increased quadriceps Tensile Stiffness would reduce peak anteromedial bundle (AM-)ACL relative strain in female knees. Twelve female cadaver knees were subjected to compound impulsive two-times body weight loads in compression, flexion, and internal tibial torque beginning at 15° flexion. Knees were equipped with modifiable custom springs to represent the nonlinear rapid stretch behavior of a normal and increased Stiffness female quadriceps (i.e., 33% greater Stiffness). Peak AM-ACL relative strain was measured using an in situ transducer while muscle forces and tibiofemoral kinematics and kinetics were recorded. A 3D ADAMS™ dynamic biomechanical knee model was used in silico to interpret the experimental results which were analyzed using a repeated-measures Wilcoxon test. Female knees exhibited a 16% reduction in peak AM-ACL relative strain and 21% reduction in change in flexion when quadriceps Tensile Stiffness was increased by 33% (mean (SD) difference: 0.97% (0.65%), p = 0.003). We conclude that increased quadriceps Tensile Stiffness reduces peak ACL strain during a controlled study simulating a pivot landing.
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morphologic characteristics help explain the gender difference in peak anterior cruciate ligament strain during a simulated pivot landing
American Journal of Sports Medicine, 2012Co-Authors: David B Lipps, James A Ashtonmiller, Edward M WojtysAbstract:Background: Gender differences exist in anterior cruciate ligament (ACL) cross-sectional area and lateral tibial slope. Biomechanical principles suggest that the direction of these gender differences should induce larger peak ACL strains in females under dynamic loading.Hypothesis: Peak ACL relative strain during a simulated pivot landing is significantly greater in female ACLs than male ACLs.Study Design: Controlled laboratory study.Methods: Twenty cadaveric knees from height- and weight-matched male and female cadavers were subjected to impulsive 3-dimensional test loads of 2 times body weight in compression, flexion, and internal tibial torque starting at 15° of flexion. Load cells measured the 3-dimensional forces and moments applied to the knee, and forces in the pretensioned quadriceps, hamstring, and gastrocnemius muscle equivalents. A novel, gender-specific, nonlinear spring simulated short-range and longer range quadriceps muscle Tensile Stiffness. Peak relative strain in the anteromedial bundle ...
Taher Baghaee Moghaddam - One of the best experts on this subject based on the ideXlab platform.
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dynamic properties of stone mastic asphalt mixtures containing waste plastic bottles
Construction and Building Materials, 2012Co-Authors: Taher Baghaee Moghaddam, Mohamed Rehan Karim, Tamalkhani SyammaunAbstract:Abstract Fatigue failure is a common problem of asphaltic concrete which can lead to pavement damage. Many studies have been conducted to find ways for increasing fatigue life of asphalt concrete mixtures. This study investigates effects of adding waste polyethylene terephthalate (PET) on Stiffness and fatigue properties of SMA mixtures at optimum asphalt contents. Different percentages of waste PET with maximum size of 2.36 mm were added to SMA mixtures. Indirect Tensile Stiffness modulus test and indirect Tensile fatigue test were conducted at temperature of 20 °C and at three different stress levels (250, 350, 450 kPa). The results showed that Stiffness modulus of mixture increased at lower amount of PET content; however, adding higher amount of PET made mixture less stiff. In addition, PET reinforced mixtures exhibit significantly higher fatigue lives compared to the mixtures without PET.
