Technology

Question 1

major assumptions of motion capture

Answer 1

body segments treated as rigid bodies
mass acts on COM of segment
COM of segment does not vary
bodies do not deform with movement or forces
fixed center of rotation for joints
markers are fixed and represent bony landmark locations

Question 2

Limitations of video analysis

Answer 2

time intensive
2d
human error in estimating joint-centers, inconsistency between frames

Question 3

advantages of video analysis

Answer 3

inexpensive

accessible

Question 4

3d motion capture require a min of ____ markers per segment

Answer 4

3

Question 5

active system

Answer 5

markers emit infrared light
optoelectric camera detects marker position in 3d space
each marker is activated individually one at a time

Question 6

passive system

Answer 6

cameras emit infrared light
markers reflect light back simultaneously
very sensitive to anything shiny in the lab

Question 7

manufacturer of active system

Answer 7

optotrak

Question 8

limitations of 3d motion capture

Answer 8

field of view
marker placement
soft tissue artifact
anthropometrics still come from tables (segment location of COM)
biased with selection of parameters

Question 9

force platforms give us

Answer 9

kinetics with 6 dof

3 forces, 3 moments

Question 10

kinemetics

Answer 10

movement only- no force

Ex: jt angles, velocity, acceleration, body position