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| Menu | Introduction |Shoe Design | Lab Tools | Activities | Glossary | References |
Part of the development of this activity was funded by an NSTA's
and Toyota's TAPESTRY grant and by the Wright Center for Science
Education, at Tufts University. The Video Analysis Activity is designed for use with Measurement
in Motion software and a Macintosh computer. However, the basic
activity should translate easily to any software that will allow
you to measure and plot angles. You can download an image for
analysis by going to the reference section of Slam Dunk Science. Video analysis, biomechanics, or kinematics studies are used in
a variety of ways by the sport researcher. For example, a scientist
interested in improving the performance of an individual cyclist
in a specific event, like the time trial, might use video analysis
to study that cyclist's position on a bicycle. The goal in this
case might be to find the most aerodynamic position for the cyclist
which would minimize wind resistance and optimize energy consumption.
The U.S. Olympic cycling team underwent extensive wind tunnel
tests in which they were video-taped and their individual form
analyzed. Feedback from this type of video analysis helped the
team to improve their performance. Figure 1 - A Cyclist in Action What kinds of studies could you think of doing to help improve
performance of this aspiring Olympic cyclist? Virtually every aspect of sport is open to study and research using
video analysis. Video analysis is regularly used with members
of our Olympic teams, from cycling to swimming, this tool is a
vital component of the U.S. Olympic Training Center's tools to
improve performance. Figure 2 - Pronation and Supination Should a researcher investigate ways to eliminate pronation and
supination completely? (Drawing by April J. Hobart) Designing shoes that provide the right amount of stability is sport
specific. For example, the design of a running shoe, where the
majority of motion can be considered straight line, differs from
the design of a basketball shoe, where the motion involved also
includes such moves as cutting, jumping, shuffling, pivoting,
as well as "straight line" running. In running the sport researcher is more concerned with ankle, or
rearfoot motion, while in basketball the researcher needs to consider
the stability of both the rearfoot and forefoot. In basketball,
the movements described above, demand better forefoot stability
as well as adequate rearfoot stability. If there is not enough
attention to the design of the forefoot components in the basketball
shoe, the player's foot might tend to roll over the midsole, possibly
causing injury. Stability of a shoe design is one of the most important research
activities that benefit from using video analysis. Without video
analysis as a tool, sport researchers and shoe designers would
be left to their "best guess." Indeed, early sport researchers
and shoe designers who intuitively understood that stability was
important, over designed shoes, and made them too rigid. A shoe
that is too rigid can also contribute to injuries or effect performance
in a negative way. With video analysis, sport researchers began
to answer the question: "What is the right amount of stability for a particular sport,
and what shoe features contribute to this stability?" In a sport research or biomechanics lab scientists use one of several
methods of video analysis to study motion, specifically rearfoot
motion, and stability as it relates to shoe design. The technique
you will use in this activity is called two dimensional analysis
of the rearfoot motion. For more information on video analysis in the sport research lab,
go to the Lab Tools section of the Slam Dunk Science Guide. This activity will focus on stability, in particular, rearfoot
motion. Video analysis will be used to study the rearfoot angle
that is defined by the leg, ankle and foot. In particular, students
will measure pronation and supination and how are effected as
a result of an athlete running barefoot, in running shoes, and
in basketball shoes. At the end of this activity students will
understand: It is important to realize that this activity only brushes the
surface of an exciting tool of science. In fact, video analysis
is a tool used by any number of scientists in studies as diverse
as animal locomotion or the analysis of design concerns in bridge
construction. After you complete this activity you can add video
analysis as another tool you can call upon to study your world. Figure 4 - X-ray cinematography and Slow motion of Starling Video analysis is a common tool used to study all types of locomotion.
These images were provided by a researcher who is studying how
muscles, bones, and tendons interact during flight. Everything from giraffes to elephants have been filmed for motion
analysis. This procedure uses Measurement in Motion software. This software,
running on a Macintosh computer, provides a good balance between
ease of use, features, and cost. An alternate procedure using
NIH Image, or analyzing video images directly off of your VCR
and monitor, can be substituted. The data collection and analysis methods have been streamlined
relative to those used in sport research labs in order to concentrate
on the process of using video analysis in the science classroom
at grades 6 through 12. For a more concise explanation of the
procedure recommended by the American Society of Testing and Materials
(ASTM) go to their web site listed in the references section of
the Slam Dunk Science Activity Guide. Figure 6 - Measurement in Motion Screen The rearfoot motion analysis is complete and the various windows
you will use are identified. It is suggested that you familiarize yourself with the Measurement
in Motion software before you start this procedure. This activity
is based on the assumption that you have done so before you start
to learn rearfoot motion analysis. Setting up Measurement in Motion Defining and Measuring the Calibration Angle Defining and Measuring the Rearfoot Angle Linking the Measurements to the Table Calculating the Supination and Pronation Angles TRA = CA degrees - RA If the Calibration angle you measured earlier (and entered in
your comment!) was 175.86 degrees, you would enter the TRA formula
as follows: TRA = 175.86 degrees - RA Setting up a Graph of Supination and Pronation Saving Your Work for Further Analysis Video Analysis like the type you performed in this activity is
used to measure the effect of a specific shoe design on the movement
of a particular aspect of the body. In this case you measured
the angle between the leg and foot. The degree of this angle,
a measure of ankle stability referred to as supination or pronation,
can contribute to injury. Everyone exhibits some amount of pronation
or supination when they walk or run. The level is subject to one's
specific biomechanics--how an individual's bones, muscles, ligaments
and tendons join in the leg, ankle, foot complex. The true value of such a measure, relative to pronation or supination,
is how it relates to what is natural motion for an individual
versus excessive. For example, it is easy to understand that if
one pronates or supinates excessively, as might happen in a basketball
game if one player's foot becomes trapped by another's, an ankle
or inversion sprain might result. This type of sprain is due to
the tearing of a ligament. In some sports, particularly basketball, ankle stability is very
important as the risk for injury, especially in the form of an
ankle or inversion sprain is high. In some sports, like tennis
and aerobics, stability is just as important in the forefoot area
of the shoe. Basically, any sport with lots of lateral movements
need shoes designed to address stability in the forefoot as well
as the ankle. In running, where the potential for excess motion is focused on
the ankle, shoe designers concentrate on devices that increase
stability only in the rearfoot region. The common injuries found
in runners that are believed to be attributable to excessive motion
are patella-femoral pain, plantar fasciitis, and Achilles tendon
injuries. Figure 7 - Anatomy of the Foot Notice the bones in this drawing of the foot. How many bones are
there? Which would be most prone to injury? Where would the fascia
and tendons be located that might be subject to injury if an athlete
suffers excessive motion? (Drawing by April J. Hobart) Figure 8 - Features that Influence Stability This is an example of the "state of the art" basketball shoe back
before sport researchers started to influence the design of shoes.
What features are present in this shoe that might promote stability?
What features would you add to this shoe that might improve stability? You should study shoes in an athletic shoe store as well as study
designs in nature to get ideas as to how you might increase the
support that a shoe might offer and in turn improve the stability
of a shoe. Collecting your own images for analysis If you have access to a sport medicine clinic in your area, you
should try to establish a relationship with them to help you collect
video for analysis. They often have high speed cameras that film
at greater than the 30 images per second possible with home video
cameras. You can collect images via a video camera but must realize that
for truly accurate image analysis sport researchers capture in
the range of 60 images or greater per second. What this means
is that your video footage might miss out on some of the range
of motion that a faster camera might capture. Even so, you can
collect images that are useful for your video analysis if you
follow a few ground rules. Note: Teachers should oversee the collection of data to insure safe
procedures are followed. Ideas for Motion Analysis You most likely have many ideas of how you might apply the techniques
learned in this activity. Here are a couple of questions to get
you started: Marking a subject for analysis of pronation or supination Two marks, separated by 20 cm should be placed on the leg. To facilitate
this process a plumb line should be dropped from the center of
the knee joint. The first mark should be placed just below the
gastrocnemius. The second mark should be placed 20 cm below the
first at the center of the Achilles tendon. Figure 9 - Leg with Markers The third and fourth marks should be placed on the barefoot or
shoes to be tested. These marks are placed on the midline perpendicular
to the sole of the shoe. These marks should be separated by a
minimum of 5 cm. Markers should be large enough to be easily visible when analyzing
the video. Sport research labs sometimes use a washable felt tip
marker or special reflective dots (a 3M product). Remember to first take a calibration shot before the subject runs
on the treadmill. Have the subject stand at the edge of the treadmill
in a comfortable manner with heels spread by 5 cm. You might want
to include in your video a calibration measure (a ruler) and a
timer (digital) as these might provide other information that
you might want to analyze.
Introduction
Sport researchers that are involved with shoe design are primarily
concerned with how the design of a particular shoe impacts the
movements of the body. In particular, a scientist might study
how the shoe effects the stability of the foot and ankle, as measured
by pronation and supination. A shoe that is badly designed can
cause an instability, like excessive pronation, that might cause
an injury. These injuries include ankle sprains or inversion sprains.
An unstable shoe can also contribute to reducing the performance
of an athlete as muscular action must be used to overcome this
instability. Muscular action requires energy, energy that is best
conserved for the final sprint in a bike race, or the winning
shot at the buzzer.
Devices used to control excessive motion in shoes are as diverse
as firmer materials used in midsoles, footbridges, and collars
or reinforcement around the midsole unit. Athletic trainers improve
stability by taping the ankle of the athlete. This is especially
true once an athlete has injured the ankle and needs to continue
to play.
It is important to keep in mind that when designing a shoe, too
much of a good thing can be detrimental. For example, it would
be quite easy to design a very stiff shoe that limits motion to
a few degrees. Would this be a good idea for a basketball shoe?
Might it be a good design for some other type of sport shoe?
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