![4
Description of Motion
Kicking the leg (leg moves anticlockwise [shown] in the
sagittal plane about a frontal axis)
Turning the head (the head moves around a vertical
axis in the horizontal plane)
Data Acquisition
Ø If you really only need data for angular
motion about a joint (pangle, angular
velocity and angular acceleration) you do
not need to collect data via an opto-
electrical device.
Ø Electro-goniometers and other device are
more portable.
Goniometers
Ø Simple goniometers like
the Leighton flexometer
are really only useful for
range of motion and
static analysis.
Ø Electro-goniometers are
easy to use and can
follow changes in
posture in dynamic
situations (velocity &
acceleration)](https://image.slidesharecdn.com/gaitanalysisangularkinematics-240828181736-a75e1dea/85/Gait-Analysis-Angular-Kinematics-pptx-pdf-4-320.jpg)
Gait Analysis & Angular Kinematics.pptx.pdf
- 1. 1 Read a chapter on Angular Kinematics Angular Kinematics Hamill & Knutzen (Ch 9) Hay (Ch. 4), Hay & Ried (Ch. 10), Kreighbaum & Barthels (Module Ι) or Hall (Ch. 11) Reporting Angles -110o +250o +ve = anticlockwise -ve = clockwise Measurement of Angles Ø Degrees (arbitrary units) Ø Radians (fundamental ratio) Ø Revolutions
- 2. 2 Radians r r r Ratio of arc/radius Circumference = 2πr therefore there are 2π radians in 360o 57.3o General Motion (a combination of both linear and angular translations) Types of Angles Ø An absolute angle is measured from an external frame of reference. Ø A relative angle is the angle formed between two limb segments. θ θ Relative Angles Ø A relative angle can be presented as degrees of flexion (opposite). or Ø presented as the angle formed at the articulation (opposite) θ θ
- 3. 3 Which are degrees of flexion and which are angle at joint? Axis of Rotation Knee Joint Centre of Rotation Ø With machines centre of rotation is usually fixed. Ø This is not the case with human joints. Axis of Rotation longitudinal axis (axis that extends within and parallel to a long bone or body segment)
- 4. 4 Description of Motion Kicking the leg (leg moves anticlockwise [shown] in the sagittal plane about a frontal axis) Turning the head (the head moves around a vertical axis in the horizontal plane) Data Acquisition Ø If you really only need data for angular motion about a joint (pangle, angular velocity and angular acceleration) you do not need to collect data via an opto- electrical device. Ø Electro-goniometers and other device are more portable. Goniometers Ø Simple goniometers like the Leighton flexometer are really only useful for range of motion and static analysis. Ø Electro-goniometers are easy to use and can follow changes in posture in dynamic situations (velocity & acceleration)
- 5. 5 Lumbar Motion Monitor Ø The LMM™ lumbar motion monitoring system was developed in the Biodynamics Laboratory at Ohio State University (W. Marras) Ø This system allows continuous monitoring of the trunk angle and subsequent analysis can quantify trunk velocities and accelerations. Gait and Running Analysis First we need coordinate data for joint centres Gait Analysis
- 6. 6 Lower Extremity Joint Angles Y X (Xheel, Yheel) (XT,YT) (XA,YA) (XH,YH) (XK,YK) Marker locations: greater trochanter femoral condyle tibial condyle lateral malleolus heel head of 5th metatarsal toe First we need coordinate data for joint centres Describing Angles Ø An absolute angle is measured from an external frame of reference. Ø A relative angle is the angle formed between two limb segments. θ θ θ21 1 6 7 5 4 3 2 θ43 θ65 5 6 Foot angle (absolute) = θ65 θ76 Metatarsal angle (absolute) = θ76 7
- 7. 7 Ø Diagrams on the next two slides Ø Thigh angle (absolute) = θ21 Ø Shank angle (absolute) = θ43 Ø Foot angle (absolute) = θ65 Ø Metatarsal angle (absolute) = θ76 Ø Knee angle (relative) = θ21 - θ43 (+ve for flexion, -ve for extension) Ø Ankle angle (relative) = θ43 - θ65 + 90o (+ve for plantarflexion, -ve for dorsiflexion) Ø Metatarsal-phalangeal angle (relative) = θ65- θ76 Hamill text, Winter (1979) pages 39-44 θ21 1 4 3 2 Knee angle (relative) = θk = θ21 - θ43 θk +ve for flexion, -ve for extension θ43 Knee Angle (relative angle) from Co-ordinate Data Ø Knee angle = θk = θ21 - θ43 Ø if θk is positive the knee is flexed Ø if θk is negative the knee is extended (dislocated?) ! 43 " = #1 tan 3 y # 4 y 3 x # 4 x $ % & & ' ( ) ) ! 21 " = #1 tan 1 y # 2 y 1 x # 2 x $ % & & ' ( ) ) Let’s step though the calculation of the angle θthigh θleg = tan-1(3.23) = 72.8 degrees (1.27 radians)
- 8. 8 Tangent Function Angular Velocity = ω change in angular displacement change in time Angular Acceleration = α change in angular velocity change in time Angular Velocity & Acceleration ! i " = i+1 # $ i$1 # 2%t ! i " = i+1 # $ i$1 # 2%t
- 9. 9 Question Hip Support Phase Swing Phase Knee Support Phase Swing Phase Ankle
- 10. 10 Graphic representations of the thigh's absolute angle (A), angular velocity (B), and angular acceleration (C) as a function of time for the support phase of walking No need to study this slide. Rearfoot Angle θleg θcalcaneus Rearfoot angle = θRF θRF = θleg - θcalcaneus Positive angle for supination Negative angle for pronation Medial
- 11. 11 Angle (degrees) Foot strike Toe-off Rearfoot Angle Inversion (supination) Eversion (pronation) 15 10 5 0 -5 -10 -15 θRF = θleg - θcalcaneus Percent of Support Phase 0 50 100 Angle-Angle Diagrams Ø Most graphical representations of human movement you will see, plot some parameter (e.g. position, angle, velocity, etc.) against time. Ø However, activities like running are cyclic and often it is useful to plot the relationship between two angles during the movement. Ø There should be a functional relationship between these angles. Knee (degrees) 0 30 60 90 120 Thigh (degrees) -50 -10 30 70 Toe-off Footstrike Running speed = 3.6 m/s Williams, 1985 Knee (degrees) 0 30 60 90 120 Ankle (degrees) 20 60 100 140 Toe-off Footstrike Running speed = 3.6 m/s Williams, 1985
- 12. 12 Knee Flexion (degrees) 170 160 150 140 130 Pronation (degrees) -50 -10 30 70 Knee Flexion vs Sub-Talar Pronation 6 minute mile pace Bates et al. 1978 Rearfoot Angle (degrees) Inversion (supination) Eversion (pronation) 20 10 0 -10 -20 Varus Neutral Valgus Knee Angle (degrees) 0 10 20 30 40 Footstrike van Woensel & Cavanagh 1992 Magnitude of GRF Ø Walking = 1 to 1.2 x Body Weight Ø Running = 3 to 5 x Body Weight (Hamill & Knutzen 1995) Ø As an example of this force magnitude, the patellofemoral joint force during squats can be up to 7.6 times Body Weight at (Reilly & Matens 1972) Ø Hamill & Knutzen text on reserve has 7 graphs of GRF’s during different types of human movement (pages 400-401) Does Nike® Air (or any substantial cushioning under the heel) reduce injury? Could it possibly increase the likelihood of injury?
- 13. 13 Impact Forces While Running Ø The sport of running causes a relatively high injury rate Ø Some argue this is due to overuse problems – basically too many foot strikes Ø While this is definitely a causative factor, others suggest the heel strike is not a natural movement pattern and is a big contributing factor. Center of pressure patterns for the left foot. A. Heel-toe footfall pattern runner. B. Mid-foot foot strike pattern runner. Ground reaction force for walking. Note the difference in magnitude between the vertical component and the shear components Ground reaction force for running. Note the difference in magnitude between the vertical component and the shear components
- 14. 14 Vertical Ground Reaction Force Time course of the GRF Impulse Time (seconds) 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Vertical Force (BW) 3 2 1 0 Run Walk GRF vs. Running Styles Percent of Support 0 20 40 60 80 100 Force (N) 1500 1000 500 0 BW Heel Striker Mid-foot striker Links of Interest Ø The issue of what is a natural foot strike pattern is a relatively hot topic these days, resulting in a resurgence of interest in barefoot running. Ø http://www.barefootrunning.fas.harvard.edu/ 4BiomechanicsofFootStrike.html Ø http://isiria.wordpress.com/2009/04/24/the-great- marketing-lie-expensive-runners-will-prevent-injury/ Ø http://www.nytimes.com/2009/10/27/health/27well.html? _r=2 Ø http://www.vibramfivefingers.com/ Ø http://www.posetech.com/
- 15. 15 Other uses of Angular Kinematics. (Angular Kinematics is used a lot in Ergonomics when trying to assess if the workers are having to adopt hazardous postures for too long? Radial and ulna deviation are both problematic Ulna Deviation Neutral wrist angle Awkward Wrist Postures Kin 380 & Kin 481 Prolonged wrist extension is believed to be a significant risk factor for carpal tunnel syndrome (Rempel 1991). Extreme wrist extension
- 16. 16 Ø Standard conservative treatment for CTS is splinting plus anti-inflammatory medication, for several weeks. Ø Usually the splint should be worn at night only. Ø Bend the tool not the wrist. Wrist Angle
- 17. 17 The preferred shape of the tool’s handle depends the body alignment during use. Desired Poor The concept of the only ideal sitting ideal posture being upright (90o at hip and knee) is wrong. Slight extensions to 110o have been show to be acceptable, if not preferred.
- 18. 18 Chair too low: Knee and hip flexion angles are too small, resulting in upper body weight being transferred to a small area at the ischial tuberosities. Shoulder Postures Angles should be below 45o
- 19. 19 Forward head posture (relative versus absolute angles?) Angular & Linear Motions Ø All points on the forearm travel through the same angle (angular displacement). Ø Each point travels through a different linear displacement Angular and Linear Displacement Ø As we saw, a radian is defined as the ratio of the distance around the arc of the circle to the radius of the circle. θ = s/r s = rθ (L => L x unitless ratio) Additional Relationships Ø vt = rω (LT-1 = L x T-1) Ø at = rα (LT-2 = L x T-2) Note that the angular units must be in radians.
- 20. 20 Maximum Linear Velocity? vt = rω Radial Acceleration Ø What is radial acceleration? Ø If velocity is a vector then even at a constant angular velocity (and hence constant linear speed) the linear velocity is changing as its directional component is changing. If velocity is changing then there must be acceleration. ar = vt2/r or rω2 Figure 9-27 Resultant linear acceleration vector (aR) comprised of the centripetal and tangential acceleration components Right Hand Thumb Rule Ø The fingers of the right hand point in the direction of the rotation, and the right thumb points in the direction of the angular velocity vector.