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Unformatted text preview: Lecture 3 SystemsSystemsLevel Modeling Overview EML 5595 Mechanics of the Human Locomotor System Outline Course Outline Journal Article Review Instructions Journal Article Review Zajac (1993) Course Outline
External Forces and Moments Neural Command 1 , 2 Musculotendon Dynamics F1
F2 Musculoskeletal Geometry (moment arms) T1
T2 Eqns 1 of 2 Motion 1 2 1 2 1. Systemslevel Modeling Systems Course Outline
External Forces and Moments Neural Command 1 , 2 Musculotendon Dynamics F1
F2 Musculoskeletal Geometry (moment arms) T1
T2 Eqns 1 of 2 Motion 1 2 1 2 1. Systemslevel Modeling Systems2. Multijoint Dynamics Multi Course Outline
External Forces and Moments Neural Command 1 , 2 Musculotendon Dynamics F1
F2 Musculoskeletal Geometry (moment arms) T1
T2 Eqns 1 of 2 Motion 1 2 1 2 1. Systemslevel Modeling Systems2. Multijoint Dynamics Multi3. Muscletendon Dynamics Muscle Course Outline
External Forces and Moments Neural Command 1 , 2 Musculotendon Dynamics F1
F2 Musculoskeletal Geometry (moment arms) T1
T2 Eqns 1 of 2 Motion 1 2 1 2 1. 2. 3. 4. SystemsSystemslevel Modeling MultiMultijoint Dynamics MuscleMuscletendon Dynamics Musculoskeletal Geometry Course Outline
External Forces and Moments Neural Command 1 , 2 Musculotendon Dynamics F1
F2 Musculoskeletal Geometry (moment arms) T1
T2 Eqns 1 of 2 Motion 1 2 1 2 1. 2. 3. 4. 5. 5 SystemsSystemslevel Modeling MultiMultijoint Dynamics Musculoskeletal Geometry MuscleMuscletendon Dynamics Systemslevel M d li Systemsl S t l Modeling Journal Review Instructions The purpose of reviewing these papers is to supplement and broaden the lab experience. Student reviews of papers will make the course more interesting, fun, and instructive. The reviews will involve both a class presentation and a written handout (see review instructions p posted on the course web site). ) The class presentation should be approximately 15 to 20 minutes (including discussion). Journal Article Review 1. The basic principles of movement coordination remain unclear, despite years of detailed recording and analysis of kinsiological data. Why? Journal Article Review 1. The basic principles of movement coordination remain unclear, despite years of detailed recording and analysis of kinsiological data. Why? 2. Forward dynamic simulation, used in conjunction with experimental measurements and optimization theory, is the most promising method for elucidating movement coordination principles. Journal Article Review O Outline: Why is understanding muscle coordination
of movement complex? Muscle function based on anatomical classification System mass matrix Forward versus inverse dynamics Do dynamicsbased models really help? dynamics Why forward dynamics? Jumping: a convincing example What do you think? Anatomical Classification Muscles are often classified based on the joint f f
torques they produce At which joints can a muscle produce a torque? Will the direction that a muscle acts to accelerate a joint always be in the same j y direction as the torque it develops? Consider uniarticular vs biarticular muscles A muscle may accelerate a j y joint it does not span more than the joint it spans Dynamic coupling System mass matrix System Dynamical Equations
q = M( q ) 1 {C( q , q 2 ) + G( q ) + R( q ) f M + E( q )} Mass matrix provides a geometric transformation between forces and accelerations Critical for d t di how f C iti l f understanding h forces contribute t ib t to joint accelerations Task dependent, that is, how muscles accelerate joints j i t varies f i from t k t task. task to t k Configuration dependent, that is how muscles accelerations joints with system configuration. Forward vs Inverse Dynamics
External Forces and Moments Neural Command 1 , 2 Musculotendon Dynamics F1 F2 Musculoskeletal Geometry (moment arms) T1 T2 Eqns of Motion 1
2 1 2 1 2 Measure or Estimate Forward vs Inverse Dynamics
External Forces and Moments Neural Command 1 , 2 Musculotendon Dynamics F1 F2 Musculoskeletal Geometry (moment arms) T1 T2 Eqns of Motion 1
2 1 2 1 2 Measure or Estimate
F1 F2
Musculoskeletal Geometry (moment arms) T1 T2 Equations of Motion 1
2 d dt 1
2 d dt 1 2 Position Data Measure
Force Plate Data (CP,Fx,Fy,Fz, Mx, My, Mz) Forward Dynamics Difficulties Computationally intensive Difficult to produce a well coordinated movement Optimal tracking e.g., minimize experimental RMS errors Hypothesize goal of the motor task e g ma imi e jjump height minimi e energ e.g., maximize mp height, minimize energy expenditure Compatibility between forward and inverse dynamics C you use jjoint t Can i t torques d i d f derived from i inverse dynamics to drive a forward dynamics simulation? Kinematic data are inaccurate (i.e., pos, vel, acc vel, estimates) Analysis of Jumping Should leg muscles be maximally activated? Should you train for strength or speed? How much does elastic energy contribute? Why do we counter move? Force buildup, stretchshortening effects buildstretchWhat is the role of uniarticular vs biarticular muscles? Why Not Use Simulation More? Considerable effort to d C id bl ff develop and test models l d d l Difficulty in finding muscle controls Systems can be unstable Complex subjectspecific models are just now subjectbeing developed EML 5595! Summary Understanding muscle coordination in multijoint multi movement is complex because muscle forces affect many body segments. Forward dynamics models provide an effective means to study muscle coordination. Forward dynamics models usually need some kind f ki d of control. O ti i ti and tracking t l Optimization d t ki techniques provide reasonable methods. Further work that combines models with experiments is needed to help elucidate coordination principles. SubjectSubjectspecific models are required to make these approaches clinically relevant. For Next Time Finish working through OpenSim Tutorial 2 Download and read Buchanan et al. (2004) J Appl Biomech 20(4): 36795 367Download and read Erdemir et al. (2007) al Clinical Biomechanics 22: 131154 131 Review list of lecture articles posted on the course web site and b prepared on M d b it d be d Monday to sign up to review three to four articles ...
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This note was uploaded on 02/15/2012 for the course EML 5595 taught by Professor Staff during the Spring '08 term at University of Florida.
 Spring '08
 Staff

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