Biomechanics Technology

Question 1

main things we will measure in biomechanics

-how

Answer 1

force
-load cell, force transducer
-force plate to get GRFs
movement
-motion capture system
-video, cameras, high speed
muscle
-electromyography
-record neural activation of muscle

Question 2

major assumptions of biomechanical modeling

Answer 2

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

Question 3

video analysis limitations

Answer 3

time intensive
-digitize points on frame-by-frame basis
2-dimensional analysis
accuracy
-human error in estimating joint-centers, inconsistency between frames

Question 4

video analysis advantages

Answer 4

inexpensive

accessible

Question 5

3-d motion capture systems

Answer 5

provide x,y,z coordinates for each marker

require a minimum of 3 markers to be placed on each segment of interest

Question 6

for 3-d motion capture, if you know where the tracking markers are in space, you know…

Answer 6

the position and orientation of the body segment

Question 7

motion capture active vs. passive systems

Answer 7

active
-markers emit infrared light
-optoelectric camera detects marker position in 3d space
each marker is activated individually, one at a time
passive
-cameras emit infrared light
-markers reflect light back to cameras simultaneously
-marker position in 3d space determined

Question 8

motion capture limitations

Answer 8

field of view
-markers must be in view of cameras
-need to determine how to deal with missing data
marker placement
soft tissue artifact (skin movement)
anthropometrics still come from tables
-segment location of COM
-segment mass
-segment moment of inertia
biased with selection of parameters

Question 9

force platform

-inverse dynamics

Answer 9

know force at foot

-can use Newton’s 3rd law up chain to get forces and moments at a specific joint of interest

Question 10

force platforms give us…

Answer 10

kinetics with 6 degrees of freedom