Dynamics

Areas of complex BIOMECHANICAL evaluation:
Biomecânica
KINEMETRY
ANTHROPOMETRY
EMG
DYNAMOMETRY
Orientation
(time)
Dimensions
Forces
linear
surfaces
volumes
Movement
Muscular
activity
Position
internal
external
Moments
(Displacement)
Velocity
Acceleration
Inertial
characteristics
mass
moment of inertia
(torques)
Pressures
Filipa Sousa
Porto Biomechanics Laboratory (LABIOMEP), Faculty of
Inverse dynamometry
Sports, University of Porto, Porto, Portugal
F = m* a
(adapted from Baumann, 1995)
Dynamics
Forward dynamics:
 F  ma
F
Dynamics
a
Inverse dynamics:
x

x

mx  F
F
1
Dynamics
Dynamics
Force transducers
Forward dynamics:
Strain gauges
F
 F  ma
a
Force and pressure transducers:
- Strain gauges
- Dynamometers
- Force Plates
- Isokinetic dynamometers
- Pressure transducers
- Isometric dynamometers
- Dynamic dynamometers
Dynamics
Force transducers
Dynamics
(Bartlett, 1997)
(Bartlett, 1997)
Force plates
Force plates
Force and torque components
which act on the performer
Vectorial expression of forces
with location (and migration)
of the centre of pressure
Force and torque components
which act on the performer
No insight on force distribution
along the contact surface
Used for foot strike patterns, balance, input for inverse dynamics
Whole-body measurements
2
Dynamics
Dynamics
Force plates
Force plate
transducers
Force plates
Data examples
They detect force and converts
(transduce) it into electrical signal
Strain gauges
Material which electrical resistance
changes with its deformation (strain)
- sensitive to temperature
- less expensive and easier to install
- more suitable for statical situations
Piezoelectric
They rely on the development of a electrical
charge by a crystal (e.g. Quartz) when subject
to a force
- drift disadvantage for static analysis
Different surfaces
Different foot strike
(Adapted from Nigg, 1986, quoted by Bartlett, 1997)
Dynamics
Dynamics
Force plates
Force transducers
Data examples
Different shoes
Ground contact forces in running (vertical component).
Force plates
Vertical GRF in standing vertical jump
(Bartlett, 1997)
Gaitway System (Kystler)
3
Dynamics
Dynamics
Force transducers
Force transducers
Force plates
Force plates
GRF vertical component (Fy)
1st Vertical Peak
Slope (gradient)1
Intermediate minimal force
2nd Vertical Peak
75 ms vertical impulse (passive)
Total vertical impulse
Support time
Double support time
Based on Soares, R. (2005)
Dynamics
Force transducers
(bw)
Values of the first peak (PC)
Force plates
18
16
14
12
10
8
6
4
2
0
Walking
Running
High J
Long J
Triple (step)
Walking Running
High J
Long J
Triple
(step)
Adapted from BAUMMAN & STUCKLE (1980)
4
Dynamics
Dynamics
Force plates
Force plates
Data examples
Vertical RF
Resultant vector
Acceleration
Horizontal RF
Deceleration
Pronation
CP migration
Lateral-medial RF
Supination
Ground contact forces in walking (3D)
(from Amadio et al., 1996)
Force plates
Dynamics
Naide Gomes - componente vertical 3 passagens
Force plates
Dynamics
Naide Gomes - componente médio-lateral 3 passagens
12
3
Nelson Évora - componente antero-posterior 4 passagens
4
10
2
6
4
Força / Peso
Força / Peso
Força / Peso
2
8
1
0
2
0
0
-2
-4
-6
-1
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0
20
40
60
80
100
-8
t
t (s)
norm
Naide Gomes - componente vertical 3 passagens
12
0
20
40
60
t
Nelson Évora - componente vertical 4 passagens
Naide Gomes - componente antero-posterior 3 passagens
15
1
80
100
norm
Nelson Évora - componente médio-lateral 4 passagens
3
0
10
2
4
-2
-3
-4
10
Força / Peso
6
Força / Peso
Força / Peso
Força / Peso
-1
8
5
-5
2
0
1
0
-1
-6
0
20
40
60
t
norm
80
100
-7
0
0
20
40
60
t
norm
80
100
0
20
40
60
t
norm
80
100
-2
0
20
40
60
t
80
100
norm
5
Force plates
Dynamics
Statics
Force plates use for balance evaluation
Stabilogrametry
t apoio =paulo1
0.167
s
Paulo
paulo1 Paulo
componente vertical
3
2
1
força normalizada
força normalizada
4
-1
-2
-3
0.5
0
-0.5
-4
0
-1
0
20
40
60
tempo normalizado
80
-5
100
Vertical:
Máx: 5.95 * Peso = 4422.2 N, aos 0.025 s
t apoio =marisa1
0.154
s
Marisa
20
40
60
tempo normalizado
marisa1 Marisa
componente vertical
80
-1
100
0
20
6
40
60
tempo normalizado
80
100
Médio-lateral:
Máx: 0.91 * Peso = 675.2 N, aos 0.029 s
marisa1 Marisa
componente antero-posterior
componente médio-lateral
1.5
1
7
0
1
força normalizada
5
4
3
2
1
-1
-2
-3
0.5
Rambling and trembling assessment for neuro-motor balance analysis
0
-4
0
-1
0
Antero-posterior:
Máx: 4.60 * Peso = 3419.2 N, aos 0.022 s
força normalizada
força normalizada
componente médio-lateral
1
0
5
força normalizada
paulo1 Paulo
componente antero-posterior
1
6
0
20
40
60
tempo normalizado
80
100
-5
Vertical:
Máx: 7.00 * Peso = 3797.0 N, aos 0.013 s
0
20
40
60
tempo normalizado
80
-0.5
100
Antero-posterior:
Máx: 4.38 * Peso = 2376.6 N, aos 0.015 s
0
20
40
60
tempo normalizado
80
100
Médio-lateral:
Máx: 1.17 * Peso = 636.4 N, aos 0.022 s
Dynamics
Dynamics
Pressure transducers
Force plates and pressure transducers
Rear foot
0%
15%
Midfoot
30%
0%
15%
Forward foot
30%
0%
15%
30%
- Foot area of contact
- Qualitative assessment
of pressure
- Anthropometry of the foot
Gait dynamometry of pre-pubertal children with different dorsal extra-loads
(from Vilas-Boas et al., 2002)
Based on Soares, R. (2005)
6
Dynamics
Pressure transducers
Data processing
Dynamics
- 2D “colour coded” displays
- 3D wire frame displays
- Force, maximal pressure and contact area
- Pressure-time integral for all regions of the foot
- Centre of pressure path
Dynamics
Dynamics
Pressure transducers
Capacitive pressure transducers
N
r x c = number of capacitors
EMED
insoles
(Bartlett et al, 1991)
3 layer construction:
A matrix of rows and columns of
conducting material, which sandwich a layer of capacitive (dielectric) material
85, 170 or 256 sensors
100Hz, 50Hz and 20Hz
Accuracy = 5%; Hysteresis = 3%; Peak up to 1270 kPa
7
Dynamics
Dynamics
Conductive pressure transducers
Piezoelectric pressure transducers
Also a 3 layer construction :
A matrix of rows and columns of
conducting material, which sandwich a layer of resistive material
Also a 3 layer construction :
A matrix of rows and columns of
conducting material, which sandwich a layer of resistive material
- Not sensitive to temperature
- Sensitive to temperature
- Much thinner and inexpensive
- Thick (3 to 4 mm) and expensive
- Calibration much more linear
but instable
- Each transducer requires individual connections
- Flexible but fragile
AMTI conform (Derrick and Hamill, 1992)
F-Scan
insoles
- Can be cut to foot size
960 sensors (5.1 mm2)
100Hz
Peak up to 1035 kPa
Dynamics
- Flexible
Developed by Henning et al, 1993)
499 sensors (23 mm2)
not
commercially 200 Hz
available
Accuracy = 2%; Hysteresis = 1%; Peak up to 1500 kPa
Dynamics
Pressure transducers
Pressure transducers
Platforms
Insoles
Hand grip
Other transducers
8
Dynamics
Pressure transducers
Dynamics
Dynamics
Pressure transducers
Dynamics
Pressure transducers
Data processing
9
Dynamics
Pressure transducers
Dynamics
Pressure
transducers
10