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Kinetics versus Kinematics for Analyzing Locomotor Coordination. D. Gordon E. Robertson, Ph.D. School of Human Kinetics, University of Ottawa, Ottawa, CANADA. Kinematic Analysis. linear position, velocity and acceleration of markers linear position, velocity and acceleration of body segments

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kinetics versus kinematics for analyzing locomotor coordination
Kinetics versus Kinematics for Analyzing Locomotor Coordination

D. Gordon E. Robertson, Ph.D.

School of Human Kinetics,

University of Ottawa, Ottawa, CANADA

kinematic analysis
Kinematic Analysis
  • linear position, velocity and acceleration of markers
  • linear position, velocity and acceleration of body segments
  • angular position, velocity and acceleration of body segments
  • total body or limb kinematics
advantages of kinematics
Advantages of Kinematics
  • easy to obtain with automated motion analysis systems
  • accuracy is easy to determine
  • requires little operator expertise
  • immediate feedback possible
disadvantages of kinematics
Disadvantages of Kinematics
  • only describes motion
  • not indicative of causes
  • difficult to discriminate important variables from idiosyncratic variables
kinetic analysis
Kinetic Analysis
  • forces and moments of force
  • work, energy and power
  • impulse and momentum
  • inverse dynamics derives forces and moments from kinematics and body segment parameters
advantages of kinetics
Advantages of Kinetics
  • defines which structures cause the motion (i.e., coordination)
  • can be used to simulate motion and describe resulting kinematics
  • can be validated against external force measurements
disadvantages of kinetics
Disadvantages of Kinetics
  • may require synchronization of several data acquisition systems (e.g., videography with force plates)
  • special training to interpret
  • more expensive and less developed software
  • invasive for direct internal measurements (muscle, ligament, or bone forces)
inverse dynamics is partial solution to invasive measurements
Inverse Dynamics is Partial Solution to Invasive Measurements
  • noninvasive with videography
  • kinematics are determined
  • direct measurements of external forces are often necessary (i.e., force platforms)
  • can be applied at several joints, simultaneously
limitations of inverse dynamics
Limitations of Inverse Dynamics
  • results apply to conceptual structures not true anatomical structures
  • cannot partition results into contributions by individual anatomical structures
  • no direct means of validating
  • modeling permits partitioning of forces and moments
sprint analysis example
Sprint Analysis Example
  • swing phase of one leg
  • world-class male sprinter
  • 50 m into 100 m competitive race (t=10.06 s)
  • analysis of hip and knee only (ankle forces not significant during swing)
slide11

Hip angular velocity, moment of force and power during sprinting

  • initial burst of power to create swing
  • latter burst to drive leg down

20.

Flexing

0.

Extending

-20.

300.

Flexor

0.

Power (W) Moment (N.m) Angular vel. (/s)

Extensor

-300.

Concentric

2000.

0.

Eccentric

-2000.

Toe-off

Touch-down

-4000.

0.0

0.1

0.2

0.3

0.4

Time (s)

hip moment
Hip Moment
  • causes rapid hip and knee flexion immediately after toe-off
  • causes hip and knee to extend in preparation for touch-down
slide13

Knee angular velocity, moment of force and power during sprinting

  • initial burst of power to stop flexion
  • small burst for extension
  • final burst to stop extension

20.

Extending

0.

-20.

Flexing

300.

Extensor

0.

Power (W) Moment (N.m) Angular vel. (/s)

-300.

Flexor

2000.

Concentric

0.

-2000.

Eccentric

Toe-off

Touch-down

-4000.

0.0

0.1

0.2

0.3

0.4

Time (s)

knee moment
Knee Moment
  • not used to cause flexion or extension during swing
  • stops knee flexion before mid-swing
  • prevents hyper-extension (locking) prior to touch-down
slide15

Hip angular velocity, moment of force and power during kicking

  • initial burst of power to create swing
  • negative work to create whip-action of leg and foot

20.

Flexing

0.

-20.

Trial: SL2CF

Extending

200.

Flexor

0.

Power (W) Moment (N.m) Angular vel. (/s)

-200.

Extensor

Concentric

1000.

0.

-1000.

Eccentric

CFS

Hit

Off

-2000.

0.0

0.1

0.2

0.3

Time (s)

slide16

Knee angular velocity, moment of force and power during kicking

  • initial power to stop flexion, bumper effect
  • negative power prior to contact to prevent hyperextension

20.

Extending

0.

-20.

Trial: SL2CF

Flexing

200.

Extensor

0.

-200.

Power (W) Moment (N.m) Angular vel. (/s)

Flexor

Concentric

1000.

0.

-1000.

Eccentric

CFS

Hit

Off

-2000.

0.0

0.1

0.2

0.3

Time (s)

normal walking example
Normal Walking Example
  • athletic male subject
  • laboratory setting
  • speed was 1.75 m/s
  • IFS=ipsilateral foot-strike
  • ITO=ipsilateral toe-off
  • CFS=contralateral foot-strike
  • CTO=contralateral toe-off
slide18

Ankle angular velocity, moment of force and power during walking

  • large burst of power by plantar flexors for push-off
  • dorsiflexors allow gentle landing and flexion during swing

10.

Dorsiflexing

0.

-10.

Trial: WN02DRMP

Plantar flexing

100.

Dorsiflexor

0.

Power (W) Moment (N.m) Angular vel. (/s)

-100.

Plantar flexor

250.

Concentric

0.

-250.

-500.

Eccentric

IFS

CTO

CFS

ITO

IFS

-750.

0.0

0.2

0.4

0.6

0.8

1.0

Time (s)

slide19

Knee angular velocity, moment of force and power during walking

  • initial burst of power to cushion landing
  • positive work to extend knee
  • negative work by extensors to control flexion at push-off

10.

Extending

0.

-10.

Trial: WN02DRMP

Flexing

100.

Extensor

0.

-100.

Power (W) Moment (N.m) Angular vel. (/s)

Flexor

250.

Concentric

0.

-250.

-500.

Eccentric

IFS

CTO

CFS

ITO

IFS

-750.

0.0

0.2

0.4

0.6

0.8

1.0

Time (s)

slide20

Hip angular velocity, moment of force and power during walking

  • some cushioning at landing
  • large amount of negative work by flexors
  • positive work by flexors to swing leg

10.

Flexing

0.

-10.

Trial: WN02DRMP

Extending

100.

Flexor

0.

-100.

Power (W) Moment (N.m) Angular vel. (/s)

Extensor

250.

Concentric

0.

-250.

-500.

Eccentric

IFS

CTO

CFS

ITO

IFS

-750.

0.0

0.2

0.4

0.6

0.8

1.0

Time (s)

questions
Questions?

Answers?

Thank you.