simply defined, a force is ? and comes in pairs of ?
push or pull, action and reaction
1 N of force is the the force required to accelerate?
1 kg of mass @ 1 m/s^2
2 types of internal forces
- compressive = pushing
- tensile = pulling
what can be used inside cadaver joints to measure forces for injury prevention
strain gauge
2 types of external forces
- contact (solid, fluid, air resistance, water resistance)
- non contact (gravity, magnetic, electrical)
the magnitude of attraction of gravity depends on?
- the mass and distance between, of objects
equation for force of gravity
- GMeMm/r^2
4 types of strain guages
- force transducers (force plates, load cells)
- springs
- peizoelectric crystals
- dynamometer
hand held dynamometers can be used to measure ?
- muscle strength capabilities
- weaknesses
what is considered the gold standard for measure internal forcers
force plate and instrumental treadmill
2 cons of the force plate and instrumental treadmill
- difficult to use in the field
- does not measure foot pressure distribution
the equation for pressure
P= Force/ Area
the most common pressure sensors work by using the?
piezoresistive effect, the change in electrical resistivity of a semiconductor or metal when mechanical strain is applied
cons of pressure sensors on feet
- unidimensional (vertical loading only)- degree of accuracy requires refinement/ testing
- -> wearing them you may change the way you walk
the F scan foot pressure system quantifies ?
force, contact pressure distribution and timing
high resolution
during forefoot running the knee is more ? the ankle more ? and the hip is in greater ? than in heel strike running
- extended, plantarflexed, extension
in a minimalist shoe, plantar pressure was higher where and lower where
higher fore foot, lower heal pressure
the instantaneous point of application of the ground rxn force
center pf pressure
pronation =
supination =
eversion (inward roll of ankle)
inversion (outward roll of ankle)
over pronation can cause?
- unnecessary stress on the ankle, internal rotation of the leg at the hip and forward pelvic tilt
some things that happen with fatigue
- increase pronation,
- increase loading on forefoot, midfoot, medial heel
- increased eversion
plantar pressure measurement provide accurate ? of kinematics and location of ? on end point effector
timing, force
plantar pressure systems can indicate difference in pressure distribution which can be an indicator of? (3)
- performance change
- fatigue
- injury potential
2 methods to approximate internal forces at the bones, tendons and joints
- inverse dynamics (using external forces to guess internal forces)
- electromyography
