EMG Analysis of Lassimus Dorsi, Middle Trapezius, and Erector Spinae Muscle Activity During Spinal Rotation: A Pilot Study

Purpose/Hypothesis: Spinal rotation is a very common movement that occurs multiple times each day during normal daily activities or even during certain sport performances. Since this motion is a contributing factor to back injuries, it will be important for physical therapists to consider this concept with rehabilitation programs for current back injuries as well as prevention of future injuries. The LD has attachments to many areas of the body, including the spine, humerus, scapula, and pelvis, which explains why this muscle also contributes to multiple actions at the trunk and upper extremity. Due to the attachment sites and the large size of the LD, this muscle is capable of influencing spinal motions during different activities. However, while there is some research regarding muscles involved with spinal rotation, there is currently limited findings for the LD and its contributing factors to spinal rotation. The purpose of this study was to improve the understanding and determine the muscle activity the LD has during spinal rotation and compare that muscle activity throughout different fixed and non-fixed positions. Methods: Participants progressed through ten spinal rotation positions (standing non-fixed rotation right/left, quadruped rotation right/left, and standing rotation right and left with arms fixed on the wall at 45°, 90° and 120° of shoulder flexion). While performing pelvis rotation in testing positions, muscle activity was recorded using EMG surface electrodes. Muscle Activity was normalized by using Maximal Voluntary Contraction (MVC) to normalize muscle activity. Findings were analyzed for significance at α=.05. Results: Significant differences were found in LD EMG activity in fixed and non-fixed movements with the ipsilateral LD being more active in fixed rotation. The ipsilateral LD EMG activity was found to be significantly greater in fixed rotation than right or left MT and ES, as well as the contralateral LD. During non-fixed spinal rotation, the ipsilateral ES EMG activity was found to be significantly greater than the right or left MT and LD, as well as the contralateral ES. Discussion/Conclusion: The findings propose the LD contributes significantly more than the MT and ES during fixed ipsilateral spinal rotation. This implies that while performing closedchain spinal rotation the LD has better positioning to participate in spinal rotation or spinal stabilization. During non-fixed positions the ipsilateral ES were most active during spinal rotation. This suggests that while performing non-fixed rotation the LD is not in optimal position to rotate or stabilize the spine. Future studies should analyze the impact on gender differences, hand dominance, and larger sample size in muscle activation. Clinical Relevance: This study is for clinicians to better understand how the LD, MT, and ES contribute to rotation of the spine. Once clinicians understand how different muscle groups affect spinal rotation, they will be able to improve the evaluation and intervention process in a variety of pathologies such as LBP. Physical therapists will be able to determine the source of pain more efficiently and prescribe more effective exercises. Understanding the actions of these muscles and how they affect spinal rotation will allow the rehabilitation process to be more time efficient and cost beneficial

EMG Analysis of Latissimus Dorsi, Middle Trapezius, and Erector Spinae Muscle Activity During Spinal Rotation: A Pilot Study

Purpose/Hypothesis: Rotation of the spine is a common movement used to complete daily activities and participate in sports. As a contributing factor to back injuries, the performance of spinal rotation is an important consideration for the rehabilitation of current and prevention of future back injuries. Muscles involved in spinal rotation have been researched, though limited findings exist for one of the largest back muscles, the Latissimus Dorsi (LD). The LD muscle contributes to many movements of the trunk and limbs given its multiple attachment sites including the pelvis, ribs, scapula, and humerus. Influence of the LD on spinal rotation has not been thoroughly researched yet, but results will play a role in the patient\u27s plan of care when treating back pain. The purpose of this study was to increase understanding of muscle activity during spinal rotation and compare muscle activity in fixed and non-fixed positions. Materials/Methods: Muscle activity was recorded using EMG surface electrodes while subjects performed left and right rotation in both standing and quadruped positions. Ten spinal rotation test positions (standing non~ fixed rotation right/left, quadruped rotation right/left, and standing rotation right and left with arms fixed on the wall at 45°, 90° and 120° of shoulder flexion) were initiated by movement of the pelvis. Using Maximal Voluntary Contraction (MVC) to normalize muscle activity, findings were analyzed for significance at a=.05. Results: When significant differences were found, the perspective muscle showed increased muscle firing compared to other muscles listed. Significance was found in the right LD between non-fixed right and left rotation and fixed right rotation. During non-fixed right and left rotation as well as fixed right rotation, the right MT showed significance. Left MT showed significant differences were shown when comparing non-fixed right rotation to fixed tight and left rotation. The MT was also significant with non-fixed left rotation compared with fixed right and left rotation. Significance was found in the right ES when comparing right rotation at 45° to left rotation at 45° and 90°, as well as right and left rotation at 120°. Significance was shown with right ES when comparing 1ight rotation at 90° to 1ight and left rotation at 120°. As for the left ES, results were significant when comparing left rotation at 45° to left rotation at 90° and 120°. Discussion/Conclusion: The findings suggest the LD contiibutes significantly to fixed position contralateral spinal rotation when compared to MT and ES. In fixed positioning, the LD may be mechanically advantaged with a positive length tension relationship to contribute to spinal rotation as established with the trends correlating with increased LD muscle activity during 90 and 120 degree fixed spinal rotation. Whereas in non-fixed positioning, the LD may be at a disadvantaged due to length tension relationship and or the lack of stability from the upper exu·emities. to contribute to spinal rotation compared to ES. Clinical Relevance: This pilot study looks at the effects of the LD, MT, and ES during spinal rotation. This study is a part of ongoing research to assess the rotational movement strategies in individuals without low back pain. During daily activities, many movements require spinal rotation movements such as putting dishes away in cupboards, taking out laundty, reaching for groceries at the store, and looking behind us when driving to check for upcoming traffic. Our findings suggest clinicians should consider the LD as a possible contributor to spinal rotation. Treatment of patients with back pain should involve thorough examination and specific interventions addressing LD strength and mobility

Thermodynamics and Statistical Mechanics of dense granular media

By detailed Molecular Dynamics and Monte Carlo simulations %of a realistic model we show that granular materials at rest can be described as thermodynamics systems. First we show that granular packs can be characterized by few parameters, as much as fluids or solids. Then, in a second independent step, we demonstrate that these states can be described in terms of equilibrium distributions which coincide with the Statistical Mechanics of powders first proposed by Edwards. We also derive the system equation of state as a function of the ``configurational temperature'', its new intensive thermodynamic parameter.Comment: Supplementary Informations adde

Sub-grid modelling for two-dimensional turbulence using neural networks

In this investigation, a data-driven turbulence closure framework is introduced and deployed for the sub-grid modelling of Kraichnan turbulence. The novelty of the proposed method lies in the fact that snapshots from high-fidelity numerical data are used to inform artificial neural networks for predicting the turbulence source term through localized grid-resolved information. In particular, our proposed methodology successfully establishes a map between inputs given by stencils of the vorticity and the streamfunction along with information from two well-known eddy-viscosity kernels. Through this we predict the sub-grid vorticity forcing in a temporally and spatially dynamic fashion. Our study is both a-priori and a-posteriori in nature. In the former, we present an extensive hyper-parameter optimization analysis in addition to learning quantification through probability density function based validation of sub-grid predictions. In the latter, we analyse the performance of our framework for flow evolution in a classical decaying two-dimensional turbulence test case in the presence of errors related to temporal and spatial discretization. Statistical assessments in the form of angle-averaged kinetic energy spectra demonstrate the promise of the proposed methodology for sub-grid quantity inference. In addition, it is also observed that some measure of a-posteriori error must be considered during optimal model selection for greater accuracy. The results in this article thus represent a promising development in the formalization of a framework for generation of heuristic-free turbulence closures from data

Microscopic origin of self-similarity in granular blast waves

The self-similar expansion of a blast wave, well-studied in air, has peculiar counterparts in dense and dissipative media such as granular gases. Recent results have shown that, while the traditional Taylor-von Neumann-Sedov (TvNS) derivation is not applicable to such granular blasts, they can nevertheless be well understood via a combination of microscopic and hydrodynamic insights. In this article, we provide a detailed analysis of these methods associating Molecular Dynamics simulations and continuum equations, which successfully predict hydrodynamic profiles, scaling properties and the instability of the self-similar solution. We also present new results for the energy conserving case, including the particle-level analysis of the classic TvNS solution and its breakdown at higher densities.Comment: 47 pages, 9 figures Supplementary Materials: 2 appendices, 3 figure

Application of the method of lines for solutions of the Navier-Stokes equations using a nonuniform grid distribution

The feasibility of the method of lines for solutions of physical problems requiring nonuniform grid distributions is investigated. To attain this, it is also necessary to investigate the stiffness characteristics of the pertinent equations. For specific applications, the governing equations considered are those for viscous, incompressible, two dimensional and axisymmetric flows. These equations are transformed from the physical domain having a variable mesh to a computational domain with a uniform mesh. The two governing partial differential equations are the vorticity and stream function equations. The method of lines is used to solve the vorticity equation and the successive over relaxation technique is used to solve the stream function equation. The method is applied to three laminar flow problems: the flow in ducts, curved-wall diffusers, and a driven cavity. Results obtained for different flow conditions are in good agreement with available analytical and numerical solutions. The viability and validity of the method of lines are demonstrated by its application to Navier-Stokes equations in the physical domain having a variable mesh