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Achilles Tendon
The major tendon in the ankle area that connects the major muscles
of the calf (gastrocnemius and soleus) to the heel bone (calcaneus).
When these muscles shorten (contract) they extend the foot. This
tendon can become inflamed through overtraining or from shoes
that are poorly designed.
American Society of Testing and Materials
The ASTM works to standardize any type of testing or measurement
used in science and business. ASTM documents are available by
contacting them, or by accessing their Home Page via the World
Wide Web.
Animal Locomotion
Many researchers use images to study how different animals move.
The best known photographer--and still some of the best pictures
ever taken of animals in motion--is Eadweard Muybridge. Researchers
have looked at locomotion in everything from single-celled organisms
to the cheetah.
Biomechanics
The study of the forces acting upon the mechanical and biological
components of an organism as they relate to some life function.
For example, the sport researcher might study how the bones, muscles,
tendons, and ligaments interact with the forces encountered during
running. By extension they would apply this knowledge to cushioning
and support systems in shoes to optimize efficiency and reduce
injury.
Bridge Construction
Video analysis can be used to determine the best design for a
bridge based on the forces that the bridge is expected to encounter.
One use of video analysis might be to video tape a bridge building
contest in physics to try and understand how different designs
influence the outcome.
Calibration Angle
This angle is a measure of supination and pronation while the
subject is standing still. The most common condition is for the
subject to exhibit a slight positive angle, or supination.
Cinematographic System
In the "early days" of sport research and motion analysis scientists
used cameras that could shoot 16mm film at rates greater than
200 frames per second. This allows researchers to capture data
from events that occur very fast. The down side to using film
is that it is expensive, both to purchase and develop, and takes
more time and special equipment to analyze.
Cut
A quick lateral movement that results in a change of direction.
Shoe design for sports that involve such movements (like basketball,
tennis, soccer and football) need to take into account the forces
generated--several times the body weight--and the frictional considerations--dependent
on the surface on which the cut takes place.
Digitize
Images, whether film or video, need to be processed into a format
that the computer can use. Video capture cards are used to capture
video and translate it into a digitized form, ready for analysis.
The sport researcher also uses this term in reference to capturing
the coordinates of markers placed on the body for motion analysis.
The procedure for motion analysis with Measurement in Motion entails
"digitizing" markers on an athlete's leg to create an angle that
can be used for analysis.
High Speed Video
Today many researchers are turning to video that can shoot at
a rate of 30 to 10,000 images per second. Some of the cameras
used for high speed video can also be fitted to "automatically"
digitize markers. The time from filming, or data collection, to
data analysis has been cut from weeks to days with such innovations.
Jump
A leaping movement that results in a vertical displacement of
the body. Shoe designers for sports that include such movements
(like basketball) need to take into account the forces generated
upon landing--greater than seven times the body weight. The designer
needs to integrate cushioning systems that attenuate the shock,
but do not interfere with performance.
Kinematics
The study of a body in motion. Researchers in kinematics may study
motion as diverse as a high jumper experimenting with a new form
to the wing-beat pattern of a hummingbird while hovering.
Marker
A coordinate placed on the body in a predetermined consistent
manner that is used to derive position. See Appendix A for specifics
on markers used to analyze pronation and supination.
Midsole
The part of the shoe between the outsole and upper. This part
of the shoe is the focal point for designs that cushion the athlete's
body from the forces generated in their sport. The midsole's contribution
to stability must also be taken into account when designing a
shoe. For example, a shoe that is very soft might be very unstable
if the foot sinks to fast into the midsole.
Optoelectronic Video System
This type of analysis system uses infrared sensing cameras and
Infrared light emitting diodes for markers. The markers are tracked
and digitized in real time to provide coordinates. This system
has the advantage of being very fast for data collection. Its
main disadvantage is cost.
Pivot
A quick movement that entails a swiveling or rotating motion.
Shoe design for sports that involve such movements (like basketball
and football) need to take into account the frictional forces
that are dependent on the surface on which the pivot takes place.
Plantar Fasciitis
This injury is caused by overtraining or improper foot alignment.
Over pronation is believed to be a contributing factor for this
condition. Fasciitis is an inflammation, strain or tearing of
the plantar fascia, the tough fibrous tissues that run from the
calcaneus to the proximal phalanges. The plantar fascia provide
support to the arch of the foot.
Pronation
This is a rather complex three dimensional movement of the foot
and ankle. It involves the turning out of the sole of the foot
(eversion) and a movement away from the midline of the body (abduction).
In technical terminology it is often referred to as dorsiflexion
of the ankle joint. Pronation is usually apparent in the final
phase a running stride, prior to pushing off, and is considered
natural. In your video analysis you look only at a simplified
two dimensional representation of this movement in the form of
the angle that can be drawn between the leg, the ankle, and the
heel of the foot. This angle is related to a "natural" or calibration
angle of this complex at a normal standing state. Pronation is
usually expressed as a negative angle relative to the calibration
angle.
Rearfoot Motion
This is the motion, most often referred to as pronation and supination,
that is visible when observing the foot from the back during the
running or walking phase of locomotion. Excessive rearfoot motion
may contribute to injuries such as Achilles tendonitis, plantar
fasciitis, and patella-femoral pain.
Run
An essentially straight line movement common to most sports. Shoe
designs for runners, focus primarily on cushioning and ankle stability.
Shoe designs for other sports, such as basketball, that include
more complex movements, like cutting and jumping, need to consider
the effects of the shoe's components designed to deal with forces
specific to each movement.
Shuffle
A lateral, side-to-side movement. Shoe design for sports that
involve such movements (like basketball and tennis) need to take
into account the forces generated--several times the body weight--and
the frictional considerations--dependent on the surface on which
the shuffle takes place.
Stability
In sport research this term is used to define the ability of the
foot to maintain a balance, relative to excessive supination or
pronation. In shoe design a stable shoe would be one that allows
for natural supination and pronation.
Stride Cycle
This includes the complete range of motion observable during walking
or running. A stride is considered the motion from first contact
of a foot through lift-off until it contacts the ground again.
Supination
This is a rather complex three dimensional movement of the foot
and ankle. It involves the turning inward of the sole of the foot
(inversion) and a movement toward the midline of the body (adduction).
Most people exhibit some amount of supination in the standing
state and the beginning of a running stride. In your video analysis
you look only at a simplified two dimensional representation of
this movement in the form of the angle that can be drawn between
the leg, the ankle, and the heel of the foot. This angle is related
to a "natural" or calibration angle of this complex at a normal
standing state. Supination is usually expressed as a positive
angle relative to the calibration angle.
Three Dimensional Analysis
This type of analysis allows for the recording and analysis of
motion in three dimensions. It requires the use of two cameras
and measures three perpendicular axes, X, Y, and Z. This system
involves solving for 11 unknown constants for each camera. The
advantage of such a system is that it provides for a three dimensional,
and therefore more accurate, model of what is taking place relative
to the movement one is researching.
Two Dimensional Analysis
This type of analysis commonly uses one camera and fewer markers
on the subject than in more complex 3-D analysis. Although it
has limitations, it was the first method used by sport researchers
and biomechanists, and is still used today by many research labs
that utilize motion analysis, and is easily adapted for student
research.
Video Analysis
Once film or video is recorded it must be analyzed. This usually
entails digitizing points off of a film or video using a special
machine, or even using tracing paper overlaid on a monitor. Video
can be captured by a computer and relevant points digitized directly
using image analysis programs such as NIH Image and Measurement
in Motion. In the motion analysis activity included here, QuickTime
movies are used to digitize points that make up an angle between
the leg, ankle and foot. This angle lets one analyze the effect
shoes have on pronation and supination.
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