Exam 3 Flashcards
Any substance that tends to flow continuously when acted on by a shear force. (ex: air, water, blood)
fluid
2 types of forces exerted on an object by a fluid environment
buoyant & dynamic
force occurs due to its immersion in fluid
buoyant
force occurs due to its relative motion in the fluid
dynamic
dynamic force is usually compromised of what 2 components…
drag and lift force
Velocity of a body with respect to the velocity of something else, such as surrounding fluid is known as…
relative velocity
when the body moves with a velocity low enough (relative) that waves and eddies are minimal it is known as…
laminar flow
in laminar flow, smooth layers of fluid molecules are flowing ______ to each other
parallel
Body moves with a velocity high enough (relative) to cause waves and eddies
turbulent flow
ex: plaque build-up causes turbulent blood flow inside arteries
fluid properties include…
density, specific weight, viscosity
mass divided by volume =
density
resistance to flow
viscosity
increases in any fluid properties lead to an increased …
magnitude of force generation (turbulence)
____ pressure and _____ temperatures will maximize fluid properties
high, low
Force acting vertically and upward in a fluid
buoyancy
which principle has to do with buoyancy? what does this principle state?
- archimedes principle
- The magnitude of buoyant force acting on a body is equal to the weight of the fluid displaced by the body or Fb = Vd y
Point at which the buoyant force acts. All of the body’s volume is equally distributed about this point.
center of volume
part of the body that has the greatest volume
center of volume
the ability to float depends on ____ ____ & ______
body weight & buoyancy (fat floats easier than muscle)
ability to float depends on the location of…
center of volume (COV)
the ____ is usually closer to the feet than the COV
COG
torque caused by weight acts through the _____
COG
torque caused by buoyancy acts through the ____
COV
when floating your hips tend to move ______ in the water, your chest moves _______
hips downward, chest upward
when floating, your hips and chest act like a force _____
couple
______ cause rotation to occur until the COV and COG are aligned
torques
if a person has a lot of adipose tissue around the midsection they can lie flat on the water. why?
COG and COV close together
Force caused by dynamic action of a fluid.
drag
a drag acts in the direction of the ___ ____ ____ flow, similar to air resistance
free stream fluid
there is less drag force at _____ altitudes
higher
3 types of resistance (drag force)
- skin friction
- form drag
- wave drag
drag derived from sliding contact between adjacent fluid layers close to the body’s surface
skin friction
Entire region within which fluid velocity is decreased around a body.
boundary layer
what affects skin friction?
- fluid velocity
- surface area of body
- roughness of body
- fluid viscosity
drag created by the pressure differential between the lead & rear sides of the body
form drag (aerodynamics!)
what affects form drag?
- body velocity
- magnitude of pressure gradient
- surface area perpendicular to the flow
drag created by the generation of waves at the interface between 2 different fluids (ex: air & water; butterfly stroke)
wave drag
what affects wave drag?
- up & down body motion
- swim speed
- moving surface water
Force acting on the body in any direction that is ┴ to the fluid flow.
Lift
increasing ___ ____ & _____ increases lift force
surface area & speed
what affects lift?
- velocity
- fluid density
- body size shape & orientation
- coefficient of lift
increased density = increased ____ due to increased _____ differential
lift, pressure
increased velocity = increased ____
lift
which principle states “regions of high velocity fluid flow are associated with regions of low pressure (& vice-versa)”
Bernoulli’s Principle
the _______ the body moves through the air or the water, the ______ the pressure differential
faster, greater
pilot puts a planes flaps (under wings) in a ____ position when landing, & ____ position when taking off
down; up
What is qualitative biomechanical analysis?
breaking down a movement into its basic elements then qualitatively examining those elements
qualitative biomechanical analysis uses ONLY the ____ of the observer
senses
define motor skills
A series of voluntary movements of the body designed to achieve a particular goal
Define performance
The manner in which all movements comprising a motor skill are executed
The measure of the outcome is known as the
result
4 requirements for valid qualitative analyses
- Prior knowledge of the skill to be analyzed
- Know the purpose or goal of performer & restrictions of rules governing the event
- Seek literature on motor skill of interest
- Know the most effective technique (not just basing it off of one successful performer)
4 steps of qualitative analysis
- description
- observation
- evaluation
- instruction
what 3 parts make up the description portion of the qualitative analysis
- Theoretical [What is the most effective technique? describe what it looks like]
- What do you want to see when you observe your subject?
- Can results be divided into distinct consecutive parts?
In a long jump, we can use information gathered from the description portion of theoretical analysis to improve distance. We can pile this information into chart-form. Explain what that looks like.
- At the very top is distance.
- Distance is the combination of (2nd row) take off distance, flight distance, landing distance
- The types of distance are reliant on (3rd row) angle, velocity and height of body
In swimming, what would the qualitative analysis chart look like?
- Time
- Start time swimming, time spent swimming
- Reaction time, technique
What occurs during the observation portion of the biomechanical analysis?
observe the subjects perforce to deterring what his or her technique actually looks like
What questions are asked during the observation portion (looking at technique of subject) of biomechanical analysis?
- whom?
- what conditions?
- where to observe?
- what to look for?
- Other senses: listening, touch, kinesthesia
rules for the observation portion
a. ) observer should instruct the performer how to proceed during testing (warm up, perform # of reps in certain time, etc)
b. ) observer should get in position AND THEN cue performer
c. ) do not make comments until performance is finished
which is the best position to analyze from, usually?
perpendicular to performance midpoint (may want front/back as well)
____ _____ affects what is seen; decided what to look for in each trial – don’t be too broad or too focused
focal point
Image capturing: watch the performance up to the ___ ____ you wish to see & then ___ ____ ____ & concentrate on the last image you saw
last point; close your eyes
what occurs during the evaluation portion
- compare the ideal technique to the observed performance.
2. identify and evaluate the errors.
What occurs during the instruction portion ?
educate the subject [providing feedback & instruction necessary to correct errors]
- repeat the analysis after correction
shoulder flexion muscles [2]
anterior deltoid, pec major
shoulder abduction [2]
middle deltoid, supraspinatus
Shoulder extension [3]
latissimus dorsi, teres major, posterior deltoid
shoulder internal rotation [2]
subscapularis, pec major
shoulder external rotation [2]
infraspinatus, teres minor
shoulder adduction [1]
latissimus dorsi
rotator cuff [4]
supraspinatus, infraspinatus, teres minor, subscapularis
elbow flexion [3]
biceps brachii, brachialis, brachioradialis
elbow extension [2]
triceps, anconeus
9 tools used for biomechanics
- eye / other senses
- anthropometry
- timing devices
- artificial optical devices
- electrogoniometry
- electromyography
- dynamometry
- accelerometry
- modeling & stimulation
The eyes & other senses are predominantly ________ & include 5 types of observations:
- qualitative
1. direct visual observation
2. indirect visual observation
3. aural
4. tactile
5. kinesthetic
which type of observation is Looking for qualitative kinetic & kinematic variables
direct visual
which type of observation is Looking at changes in the environment caused by the performance
indirect visual (foot print in sand, hurdles knocked over))
which type of observation deals with (acoustic/auditory), listening
Aural
examples of aural
blood pressure, injuries, rhythm of a movement pattern
which type of observation deals with touch; SPOTTING someone in gymnastics or weightlifting
tactile (touch)
which type of observation is Observation made by yourself, if the movement “felt” right.
kinesthetic (golf swing)
measures of the human body are referred to as
anthropometry
examples of anthropometry
- mass of body segment
- heigh weight
- COG in sports
anthropometry tools:
tape measure, scale, caliper, underwater weighing tank, bod pod, MRI
Used to record the speed of the body and its parts. Describes movement patterns and may influence other variables (ex: torque)
chronoscope (timing device)
timing device examples
stop watch to time movements
switch mat/jump mat
force plate
Quantitative, can save a permanent record
artificial optical devices (photography & cinematography)
Used a Zoopraxiscope (like a flip movie) to analyze gait in horses.
Muybridge (1830-1904)
- Studied gait using photography & cameras
2. Investigated how slow and fast speed cameras can be used to analyze human movement
Braune & Fisher
why is single image photography useful
- used to analyze specific body positions
- graph sequence cameras
- rapid advance
Multiple exposure photograph (strobe light type pictures)
stroboscopy
todays high speed cameras are ____ - _____ Hz
2000 - 6000
the greater the Hz the greater the ____ of _____
detail of motion
our eye operates at ___-___ Hz per second
10-12
Synchronize a camera with an x-ray or fluoroscope. Bones filmed in motion.
cineradiography
Used to make 3-D pictures of the body and internal structures
MRI (magnetic resonance imaging)
Video cameras and computers used together. The computer “grabs” the image and then digitizes (makes a stick figure image) the subject –
The subject wears reflective markers during the recorded session)
Computerized videography
computers can automatically calculate what 6 things
displacements, velocities, accelerations, moments of force (torque), center of gravity (COG), statistics
electrogoniometry was designed by whom
karpovich
an electrogoniometer is a goniometer with a _____ rather than a protracted. what does it do? problems?
potentiometer. measures joint angles & sends to printouts. lacks spatial orientation of limb & can be cumbersome
ED goniometry
movement in multiply planes; allows measurement of joints out of visual line of sight; expensive! helpful in twisting/turning movements
Recording electrical activity (motor unit action potential) of muscle during contractions
Electromyography (EMG)
how does EMG work
Metal disks (surface electrodes) or fine wires (needle electrodes) are used to pick up the electrical signal
which are more accurate for EMG - needle or surface electrodes?
Needle electrodes give more accurate readings than surface electrodes; they go directly into the muscle tissue
In an EMG the electrical signal is recorded by the computer. • The _____ of the signal is proportional to the _____ of the movement & the amount of muscle fibers contracting
magnitude, velocity
Measures force production in the body.
Dynamometry
Dynamometry was first used in the _____’s
1960’s
3 types of dynamometry devices
- hydraulic or spring
- cable tensiometers
- strain gauges
- force plate platform
- foot plate/pressure plate
measures centrifugal force in hammer throw; pulling forces
Cable tensiometers
what is an example of hydraulic or spring devices
hand grip dynamometer;
examples of strain gauges
sport equipment; canoe & kayak paddles; show insoles; bike pedal
Force plate platform measures what? records what? estimates what?
measures: GRF
records: force time in 3 axes (xyz)
estimates: compressive forces & torques
force plates can be as thin as _____ & can be used in ____ or ____ under the feet
paper; shoes; mat
what do foot plate/pressure plates help investigate?
plantar pressure, gait & balance patterns
what type of research is foot plate/pressure plate used for
disease populations (prescribe diabetic orthotic) or lifting studies
Use of devices to measure acceleration, estimate joint forces
accelerometry
some accelerometers can attach to _____, recording acceleration of the movement. example?
limbs. wii remote
Mathematical modeling of a living body’s characteristics, used for predicting performance.
modeling & stimulation
modeling & stimulation uses ______ information from ________ calculations
quantitative; biomechanical
example of modeling & stimulation
crash test dummies
