lab 5: force plate Flashcards
what does force plate measure
measures the forces exerted by the body
in gait/balance activities, what are force plates used to measure (2)
1) GRF
2) centre of pressure
what is newtons 3rd law
for every force, there is a reaction force that is equal in magnitude and opposite direciton
GRF acting in contrast to your body pushing on the floor is an example of what law of newtons
newton’s 3rd law
where and during what activities does ground reaction force act
act on the foot during walking, jumping, running
what are the 3 components of ground reaction force
has 3 components
(vertical, med/lat, ant/post)
why does ground reaction force increase from 0-10% of stance
you are double support (so it will never be over 100) but it is increasing because you are adding weight (body weight shifting onto the leg)
be able to explain the 2 peaks and 1 valley in the ground reaction force
.
the first peak of vertical ground reaction force is during what part of phase
loading response/midstance
the second peak of vertical ground reaction force is during what part of phase
preswing/pushoff
what are the ground reaction force measures
peak (max ground reaction force)
loading rate = peak/time (it takes to get to peak)
pattern recognition (principal component analysis0
what is loading rate of GRF
peak/time (that it takes to get to the peak)
what is an example of pattern recognition in terms of ground reaction force measures
principal component anaylsis
what is cop (centre or pressure)
single point which a single force is considered to act through
=point where GRF is considered to act on the foot
where is the point where GRF is considered to act on the foot
the centre of pressure
what are the 3 components pf the force plate
top plate
bottom plate
sensors in between the plates
what is another name for common force plate sensors
transducers
what are the 2 common sensors of force paltes
piezoelectric
strain gauge
explain piezoelectric sensors
consists of a crystal when pressure is applies, there is a change in electrical current
which sensor type does this apply to: consists of a crystal when pressure is applies, there is a change in electrical current
piezoelectric
explain strain gauge sensors
metal plate/beam is deformed, changes electrical resistance
which sensor type does this apply to: metal plate/beam is deformed, changes electrical resistance
strain gauge
during force plate sensors, the changes in electricity are calibrated to what
the known forces at the manufacturer
what is the wii fit
cheap force plate with 4 strain gauges
what can the WII fit measure (2)
1) vertical GRF (not other direction)
2) COP
force plates provide an analog or digital signal
analog
true or false: force plates provide a digital signal
false, analog
when is analog converted to a digital signal in force plates
analog is converted to digital signal prior to computer storage
analog is a continuous waveform or discrete packets of data
continuous waveform
digital is a continuous waveform or discrete packets of data
discrete packets of data
does radio use analog or digital
analog
be able to see the difference in graphs for analog vs digital
continuous signal is associated with analog or digital
analog
discrete packages are associated with analog or digital
digital
what is the sampling frequency (rate) when converting analog to digital
how often you convert the analog signal the digital signal
=number of samples you take per second (Hz=samples/second)
what is the formula for sampling frequency (rate)
=number of samples you take per second (Hz= samples/second)
sampling frequency should be x2 the maximum frequency within the analog system according to what theroem
Nyguist
Nyquist theoem states that sampling frequency should be x2 what
the maximum frequency within the analog system
Nyquist theoem states that sampling frequency should be BLANK times the maximum frequency within the analog system
2 times
what is the maximum frequency of ground reaction force during walking
15Hz
if the maximum frequency of ground reaction force during walking is 15 Hz (analog), what should the sampling frequency be
15 x 2
=30 Hz
