Pressure Systems Flashcards
What is pressure? Can you explain the formula.
Pressure is ratio of force to the area over which force is distributed
How is pressure distribution measured? What are two types of pressure sensors.
Resistive and Capacitive pressure sensor systems
Describe how a Resistive pressure sensor system works, and give an example.
2 electric conductive sheets separated by thin layer of non-conducting dielectric material
When normal force applied, middle layers compressed and conductive foam particles touch
Surface area increased > current through sensors increase
Results in change in magnitude of measured electric charge (lowering electrical resistance)
E.g. Phone touch screen
Describe how a Capacitive pressure sensor system works, and give an example.
Two electric conductive sheets separated by a thin layer of a conducting material (dielectric elastic layer)
Normal force is applied to the sensor, the middle layer is compressed and bends
Reduction of the distance b/t sheets
Change in the magnitude of the measured electric charge proportional to pressure
E.g. Novel Pressure System
What are the benefits of Novel Pressure Sensors?
Basic software OS
Accurately measures foot pressure static and dynamic
Records automatically when foot contacts platform
Links with novel database and report software
What do we look for when purchasing a Pressure Sensor? What is the optimal setup for each specification?
Sensor size: Smaller the better-more accurate, Novel 1.9mm
Number of sensors: Wider range and number of sensors better (99 sensors, 1200 range kPa)
Frequency: Higher frequency more accurate up to certain pt. 50-400hz Novel
Hysteris: Lower better, refers to lag between input and output. Novel <7%.
What are pressure systems primarily used for?
Plantar Pressure: Measuring pressure distribution between foot or shoe and the ground
What are the two ways plantar pressure or pedobarographic measurement is measured?
Platforms or insole
What are the limitations of the two plantar pressure measurement systems? Explain for platform.
Small size causes targeting problems for performer
Distribution of pressure altered if platform is covered with sports surface
What are the limitations of the two plantar pressure measurement systems? Explain for Insole.
Require cabling & battery pack to be worn
Insole may alter pressure distribution cos of thickness
records only normal Component of stress (pressure) and not tangential components (sheer)
Susceptible to mechanical damage and crosstalk between individual sensors
Durability of sensors is function of thickness
What are the differences between the two types of Pedobarography? Examples of each?
Both are collection and analysis of time series data
Dynamic: during dynamic activities (e.g. Gait)
Static: during postural activities (e.g. standing still)
Apart from plantar pressure, what can pressure systems also measure?
Palmar pressure: measuring pressure distributions between hand/fingers and ground or an object
How does data output from pressure distribution look like?
- Color coded matrix graphs
- Wire frame diagrams
- Isobarographs
- 3D surface contour data w pressure distribution info under the foot
What are the different data we can derive from pressure distribution output? What are the SI units for each?
- Peak pressure (kPa): highest pressures under thefoot
- Pressure-time integral (kPa/s): impulse, area
- Contact time (in s or ms): time force/pressure is applied
- Contact area (in cm2): amount of plantar surface touching the ground
- Centre of pressure trajectory/excursion
Pressure outcomes can be differentiated to either ____ ____ or ________ ____
Entire foot or anatomical regions
Applications: What did research with Diabetic patients with neuropathy suggest?
Forefoot and rearfoot peak plantar pressure ratio: Significantly higher in patients with severe neuropathy
F/R Ratio more than 2, can predict foot ulceration with same specificity as peak pressure > 6kg/cm2
Applications: What did research with Rheumatoid arthritis patients suggest?
Forefoot joint damage in rheumatoid foot related to increased pressure under forefoot
High forefoot pressure > associated with pain during barefoot walking
Applications: Obesity and peak pressure values
Lack of differences as compared to previous studies
Relatively lower increase of peak pressure values in limited parts of foot (limitation was recruitment of participants)
Applications: Sports technique (Football)
Found loading patterns w higher pressure values than those observed during normal running
Cutting: medial part of foot
Sprinting: 1st & 2nd ray
Kicking: lateral part of foot
http://www.ceuarmy.com/BSFAFpdf.pdf
No global effect of two surfaces (grass and red cinder)
Applications: Footwear & Orthoses (pressure v speed)
Peak plantar pressure increased linearly for Hallux and Heel as speed increases
Forefoot > quadratic effect (used quadratic equation to find best fit)
Implications: range of speed > diff plantar regions of normal foot function > dictate type of materials used development of walking shoes or orthoses
Applications: Unstable shoes
There was a decrease in movement variability in MBT (unstable) shoes from training intervention to level of conventional shoes after 10 weeks
Initially 35% higher variability, decreased by 30% to almost equal.
