Motion AnalysisSummer Course Speaker: Yi-Jung Tsai Date: 2011/07/13 Motion Analysis Laboratory
Outline • Part I: Introduction of motion analysis • Basic introduction • Research methods in motion analysis • Instrumentation • Data collection • Data analysis • Part II : Application • Gait analysis • Clinical application • Sports medicine
Part I: Introduction of motion analysis • Basic introduction • Research methods in motion analysis • Instrumentation • Data collection • Data analysis
Introduction • What is motion analysis ? • When and why do we need to analyze motion? • What knowledge do we need before research?
Introduction • Kinematics (運動學） • Kinematics is concerned with the geometry of motion and deal with relationships among displacement, velocity, acceleration, and time without any reference to the cause of motion To describe the motions we see
Introduction • Kinetic (力動學) • Kinetics deal with relationships among forces, mass, and motion of the body, it is concerned with the cause of motion To understand why the motions occur force / torque
Introduction • Anthropometry (人體測量學） • Involving body and limb measurements • mass of segment • location of mass center • segment length • center of rotation • angle of muscles • mass and cross-sectional area of muscles • moment of inertia
BM = Total Body Mass; BH = Body Height I = %I*Segment Mass*Segment Length2
Introduction • Muscle and joint biomechanics • Characteristics of muscle and joint - length-tension relationship - force-velocity relationship - joint type
Introduction Electromyography (肌電圖） - the study of muscle electrical activities providing information about the control and execution of voluntary movement
Steps of motion analysis Setting the purpose Choosing the appropriate instrumentation Data collection Data analysis Results and interpretation
Instrument_ kinematics （Electro) goniometers (量角器） - a device for measuring joint angles
Instrument_ kinematics • Accelerometer (加速規） - a device that measures acceleration • types: • strain gauge • piezoresistive • piezoelectric
Instrument_ kinematics • Imaging system • Cinematograph • digital video • charge-couple device (CCD) cameras: - Motion analysis, VICON, Qualisyssystem
Eagle Digital RealTime System • 1-2000 Hz selectable frame rates • Passive (retroreflective) markers
EVa Real-Time Software (EVaRT) • 3D Display • XYZ Graphs • Analog Graphs
Instrument_ kinetic • Force transducers - measure the applied forces • types: • Piezoresistive • Piezoelectric
Instrumentation_ kinetic • Force plate - most commonly used type of force transducer - measuring ground reaction force (GRF) • type: • Strain gauge • Piezoelectric
Instrumentation_ kinetic Kistler force plate
Instrumentation_ kinetic Pressure sensor
Instrument_ EMG • Types: - Surface EMG - Wire EMG - Needle EMG
Steps of motion analysis Setting the purpose Choosing the instrumentation (kinematics, kinetic, EMG…..) Data collection Data analysis Results and interpretation
Data collection Calibration - to define the global coordinate system
Data collection Preparation - measurements of basic data - placement of EMG electrodes - marker attachment on the landmark (marker set) - others
Data collection Placement of EMG electrodes Others: setting the appropriate mode - sampling rate - collection time - amplify….
Steps of motion analysis Setting the purpose Choosing the instrumentation (kinematics, kinetic, EMG…..) Data collection Data reduction & analysis Results and interpretation
Data reduction & analysis Signal output Signal processing - data smoothing - interpolation - filter: low pass, band pass, high pass filter…... - re-sampling Setting the appropriate parameters
Planes of Motion: 1 = Frontal plane 2 = Sagittal plane 3 = Transverse plane
Data analysis Step 1: compute b Step 2: compute a Step 3: compute g • Resolve the joint angles: • Calculation - kinematics • Translation and Rotation of different coordinate systems
Data analysis • Calculation • kinetic(ground reaction force, joint moment) • Inverse dynamics • EMG: • Rectified • Linear envelope • Integrated……..
Take home message • How to choose the appropriate instrument? - according to the research purpose - understanding the pros and cons • How to collect data well? - following the manuscript - setting the appropriate mode • What should be noticed in data analysis? - avoid distortion after signal processing - understanding the limitation and problems of different computing method • What should be noticed while reading the report? - does the result make sense?
Part II : Applications • Projects in motion analysis laboratory • Gait analysis • Clinical applications • Sports medicine
Gait analysis Bipedal locomotion, or gait, is a functional task requiring complex interactions and coordination among most of the major joints of the body, particularly of the lower extremity.
Anatomical considerations_ hip joint • flexion-extensionoccurs about a mediolateral axis. • adduction-abduction occurs about an anteroposterior axis. • internal-external rotation occurs about a longitudinal axis.
Anatomical considerations_ knee joint 3 degrees of freedom of angular rotation are also possible during gait. The primary motion is knee flexion-extension. Knee internal-external rotation and adduction-abduction may also occur, but with less consistency and amplitude among healthy individuals owing to soft tissue and bony constraints to these motion.
Anatomical considerations_ ankle and foot Ankle motion is restricted by the morphological constraints of the talocrural joint, which permits only plantarflexion (extension)anddorsiflexion(flexion). In gait analysis as a rigid segment, the foot is required to act as both a semirigid structure and a rigid structure that permits adequate stability
Gait Cycle Stance phase:60%, including foot flat, midstance, terminal stance, and pre-swing. Swing phase: 40%, including initial swing, midswing, and terminal swing.
Clinical Applications • Musculoskeletal pathology • polio, muscle atrophy, amputation, osteoarthritis rheumatoid arthritis, trauma • muscle weakness, restricted joint mobility, pain • Upper motor neuron pathology • cerebral palsy, stroke, brain trauma • combine spasticity, sensory disturbance, error in control mechanisms
Chair-rise in Patients after Total Knee Arthroplasty Fong-Chin Su, Kuo-An Lai, Wei-Hsien Hong ClinBiomech 13:176-181, 1998
Objectives • To understand the biomechanics and compensatory mechanisms of chair-rise in patients after TKA. • Functional evaluation of pre-op patients compared to the normal elderly.
subject N age body height body weight (yr) (cm) (kg) 61.0 ± 9.90 58.2 ± 10.5 73.3 ± 14.0 159.5 ± 6.9 154.5 ± 5.2 157.0 ± 5.7 60.7±6.67 61.2 ± 7.60 64.8 ± 8.00 normal elderly OA patient TKA patient 12 14* 12* OA patients ( 10 bilateral, 4 unilateral ) TKA patients ( 8 unilateral, 4 bilateral ) * : Subjects
camera A/D computer converter interface disk storage Experiment Setup
Sit-to-Stand a b c d a - b : flexion momentum phase b - c : momentum transfer phase c - d : extension phase * 4 chair heights: 115%, 100%, 80%, 65% knee height