University of Vermont

About: University of Vermont is a education organization based out in Burlington, Vermont, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 17592 authors who have published 38251 publications receiving 1609874 citations. The organization is also known as: UVM & University of Vermont and State Agricultural College.

The effects of abdominal muscle coactivation on lumbar spine stability.

Abstract: STUDY DESIGN: A biomechanical model of the lumbar spine was used to calculate the effects of abdominal muscle coactivation on spinal stability. OBJECTIVES: To estimate the effects of abdominal muscle coactivation on lumbar spine stability, muscle fatigue rate, and lumbar spine compression forces. SUMMARY OF BACKGROUND DATA: The activation of human trunk muscles has been found to involve coactivation of antagonistic muscles, which has not been adequately predicted by biomechanical models. Antagonistic activation of abdominal muscles might produce flexion moments resulting from abdominal pressurization. Qualitatively, antagonistic activity also has been attributed to the need to stabilize the spine. METHODS: Spinal loads and spinal stability were calculated for maximum and submaximum (40%, 60% and 80%) efforts in extension and lateral bending using a previously published, anatomically realistic biomechanical model of the lumbar spine and its musculature. Three different antagonistic abdominal muscle coactivation patterns were imposed, and results were compared with those found in a model with no imposed coactivation. RESULTS: Results were quantified in terms of the sum of cubed muscle stresses (sigma sigma m3, which is related to the muscle fatigue rate), the maximum compressive loading on the lumbar spine, and the critical value of the muscle stiffness parameter (q) required for the spine to be stable. Forcing antagonistic coactivation increased stability, but at the cost of an increase in sigma sigma m3 and a small increase in maximum spinal compression. CONCLUSIONS: These analyses provide estimates of the effects of antagonistic abdominal muscle coactivation, indicating that its probable role is to stabilize the spine.

Mechanical properties of vascular smooth muscle cells in situ.

Abstract: ALTHOUGH the histology and ultrastructure of smooth muscle cells have been studied extensively there is little direct evidence concerning their mechanical properties. Their small size1,2 and lack of tendon connections have prevented them from being mounted on a myograph, as has been done with striated muscle fibres3. Moreover, their multiplicity and optical properties make it difficult to visualise them in whole smooth muscle preparations. Although isolated smooth muscle cells4–6 can be seen to contract when stimulated, it has not been possible to measure the forces they develop. There are, therefore, still serious doubts about the extent to which the mechanical properties of whole smooth muscle preparations are an accurate reflection of the properties of smooth muscle cells. We have therefore developed a technique to obtain mechanical data from a smooth muscle preparation which only contains about 1,000 smooth muscle cells, and which is thin enough for the cells to be visualised by Nomarski interference microscopy7. This technique provides for the first time the means to study the mechanical properties of smooth muscle cells in situ.