Samuel Howarth
CMCC, Graduate Education and Research, Faculty Member
- I have received a B.Sc. in Kinesiology with a Joint Honours in Mathematics (2004) as well as an M.Sc. (2006) and Ph.D... moreI have received a B.Sc. in Kinesiology with a Joint Honours in Mathematics (2004) as well as an M.Sc. (2006) and Ph.D. (2011) in Biomechanics from the University of Waterloo. During my research career, I have conducted biomechanical research using both experimental (in vivo and in vitro) and theoretical (computational modeling) approaches. My doctoral research investigated how passive tissue damage in the lumbar spine under acute as well as repetitive shear loading is influenced by modulating factors such as morphology, bone density, posture, compressive load and shear load rate. Findings from this research will be used to enhance our understanding of injury mechanisms so that future interventions may be developed to reduce the incidence of shear related low-back injury.edit
Segmental instability, characterized by excessive or aberrant movement of the vertebrae can be assessed quantitatively using mechanical characteristics within a region of minimal resistance called the neutral zone. The diagnosis of... more
Segmental instability, characterized by excessive or aberrant movement of the vertebrae can be assessed quantitatively using mechanical characteristics within a region of minimal resistance called the neutral zone. The diagnosis of instability is often used to decide whether or not to surgically fuse the vertebrae. Alterations in flexion/extension posture cause changes in both contact area and spacing between articulating facets that may lead to changes in the mechanical response of the functional spinal unit (FSU) within the neutral zone. This investigation quantified neutral zone (NZ) length under anterior and posterior shear loading and the influence of posture on the shear NZ characteristics of the vertebral joint. Thirty porcine cervical FSUs (15 C34 and 15 C56) were tested. Endplate area was calculated from measurements of the exposed endplates while facet angles were measured from X-rays taken in the transverse plane. Specimens were exposed to a 300 N compressive preload followed by a test to determine flexion/extension NZ limits. These limits were used as target angles during shear passive tests performed in extended and flexed postures. Displacement rate during shear passive tests was 0.2mm/s and five cycles of anterior-posterior shear were performed to a target of ±400 N in a randomized order of extended, neutral and flexed postures. Shear NZ length and average stiffness were quantified. Stiffness within the shear NZ was 67 N/mm in the neutral posture. Extended postures produced a 37% (p<0.0001) increase in shear stiffness within the NZ compared to both flexed and neutral postures. Posture did not influence shear NZ length. Therefore, a true region of zero stiffness does not exist during shear loading with a baseline compressive load. Neutral zone length for the porcine FSU exposed to shear load was not influenced, despite known changes in facet articulation, by changing posture. Average stiffness increased likely as a result of increased contact area and force in extension. The results from this investigation demonstrate that postural deviation of the vertebral joint is not likely a significant confounding factor when assessing segmental stability.
Research Interests:
Research Interests:
Research Interests: Skeletal muscle biology, Spine, Postural Control, Humans, Movement, and 17 moreFemale, Male, Orthopedics, Abdominal Muscles, Wheelchairs, Electromyography, Posture, Clinical Sciences, Tes, Gear, Adult, Public health systems and services research, Wheel, Reference Values, Equipment Design, Muscle Activity, and Isometric Contraction
Research Interests: Kinetics, Risk assessment, Low back pain, Lumbar spine, Humans, and 18 moreApplied Ergonomics, Female, Male, Gender Difference, Young Adult, Electromyography, Medical Physiology, Posture, Adult, Sex Factors, Shear Strength, Shear Force, Risk Assessment, Upper Extremity, Lifting, Weight Bearing, Muscle Activity, and Biomechanical Phenomena
Research Interests:
Research Interests:
Research Interests:
Research Interests: Mechanical Engineering, Biomedical Engineering, Skeletal muscle biology, Spine, Exercise therapy, and 14 moreHumans, Computer Simulation, Applied, Compressive Strength, Male, Young Adult, Back, Muscle contraction, Weight Bearing, Equipment Design, Exercise Test, Equipment Failure Analysis, Tissue Mechanics (Applied Biomechanics), and Abdomen
Research Interests:
Research Interests:
Research Interests: Engineering, Biomechanics, Skeletal muscle biology, Kinetics, Injury Prevention, and 18 moreStability, Human Movement Science, Humans, Male, Resistance Training, Exercise, Abdominal Muscles, Electromyography, Mechanical Stress, Adult, Muscle contraction, Joints, Muscle Force, Upper Extremity, Weight Bearing, Muscle Activity, Biomechanical Phenomena, and Lumbosacral Region
A thesis presented to the University of Waterloo in fulfillment of the thesis requirement for the degree of Master of Science in Kinesiology ... I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis,... more
A thesis presented to the University of Waterloo in fulfillment of the thesis requirement for the degree of Master of Science in Kinesiology ... I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted ...