TheStandardNO.1 2007

/10Literature update Dr. Ed Biden

/06Tracking the motion of footballs in three dimensions

/04Vicon ProfilesDr. Richard BakerVicon Setting the standard for Life Sciences

VICON MOTION CAPTURE TECHNOLOGY IS PLAYING A LARGE PART INBALL STATE UNIVERSITY’S PROMISING FUTURE

Collaborations form a brighter future

CONTRIBUTIONS BYDR. ERIC DUGAN

Muncie, Indiana may not seem like a hotbed of research but it is home to Ball State University, one of the United State’s premier science and technology researchcenters. Ranked by the Princeton Reviewas one of the best universities in theMidwest, Ball State is maintaining thatposition by diligently enhancing both thestudents’ and community’s relationshipand experience with the school. Almost

unexpectedly, Vicon motion capture technology is playing a large part in Ball State’s promising future.

Since 2003 Dr. Eric Dugan has headed the Biomechanics Lab at the School ofPhysical Education, Sport, and ExerciseScience and is masterfully guidingundergrad and graduate students throughthe understanding of the mechanical and

Art of the BowIn 2005, Dr. Dugan and Hans Sturm from the School of Music collaborated to create Art of the Bow with bassist François Rabbath, a groundbreaking DVD that records what is known as one of the world's "sweetest swings" throughmotion-capture technology and 3-D animated graphics. An innovative pedagogical tool that fuses art and science, the instructional DVD has earned accolades from musicians around the world.

Sturm, a bassist himself, has studied thelegendary François Rabbath’s intricatebowing techniques for more than 5 years.Following a coaching session in Paris,Sturm approached Dr. Dugan about a project to capture the subtleties ofRabbath’s renowned technique. Using aVicon MX system, the team captured thenuances of the bassist’s fingers, wrist and bow arm to create a graphically, realistic, interactive teaching tool.

While traditional music publications orvideos are limited to illustrations or

photographs from a single viewpoint, the DVD's four camera angles enable a student to select viewing options thatfocus on an angle of particular interest. As a result of the pioneering in-depthstudy and its accompanying performancesand interviews, the DVD has receivedinternational acclaim.

Digital MediaDr. Dugan is also working with Ball State University’s Center for Media Design (CMD) on several projects outside the normal boundaries of a traditional exercise science program. The projects,still in the developmental phase, fall intotwo broad categories. First, the two groupsare exploring ways to integrate the center’seye-tracking and the biomechanics laboratory’s motion capture capabilities.This will provide the ability to betterunderstand how visual stimuli affect an individual’s movement and postural control. Secondly, they are investigatingthe potential uses of motion capture in conjunction with the CMDs expertise in digital media to develop interactive learning environments for students in a variety of academic programs.

Capturing F. Rabbath with Vicon MX cameras

“Innovative pedagogical tool “that fuses art and science”

/02neuromuscular characteristics of humanmovement. A broad research agendaencompassing injury mechanisms, theeffectiveness of clinical interventionstrategies, structural limitations, and theinfluence of both short-term (acute) and

long-term (chronic) exercise protocols onvarious biomechanical aspects of humanhealth and performance. This has led toseveral interdisciplinary collaborationswithin the university and the local medical community creating a wealth

of opportunities for both student and school. The lab’s uniqueness lies within itsability to apply movement analysis to avariety of situations beyond the standard gait or rehabilitation applications.

Vicon Setting the standard for Life Sciences

Community InvolvementMidwest Health strategies MotionAnalysis and Therapy Complex

Unique collaborations are not in shortsupply for Ball State University’sBiomechanics Lab. In May 2006, theMidwest Health Strategies Motion Analysisand Therapy Complex opened in partnershipwith Dr. Dugan’s lab, featuring a 1,500square foot motion analysis facility.Midwest Health Strategies, an affiliate of regional healthcare provider CardinalHealth System, is the area’s most comprehensive provider of physical rehabilitation therapy services. As a resultof the unique collaboration, the outpatienttreatment and research facility is one ofthe first of its kind to open outside of aresearch hospital in a large, metropolitancommunity. “Two of our community’s very substantial resources have cometogether once again to not only provide an outstanding and innovative service, but hopefully a model for others to followin the delivery of healthcare.”, commentedMidwest Health Strategies’ COO Gregg J. Altobella.

Created to provide unprecedented community access to innovative medicaltechnology, the complex will also serve as an immersive learning experience for students. A 10 camera Vicon MX40motion capture system provides critical rehabilitative data analysis as well as ahands-on learning. “It prepares studentsto work in healthcare related motionanalysis facilities around the country,” said Dugan. “A few of our recent graduateswho have worked in the campus lab havesaid that experience with 3-D technologiesallowed them to move right in to a similarjob after graduation.”

FutureThe collaborative and entrepreneurialnature of the biomechanics lab has built a strong foundation to provide both undergraduate and graduate students aunique, ‘hands on’ learning experience. It has also expanded the lab’s capacity to engage in both clinical and sport/exercise research.

Some examples of the research takingplace in the lab include studies to:

• compare functional outcomes in patients following total hip replacements via different surgical techniques

• determine the metabolic and muscular adaptations of cycling with independent cranks

• determine the effects of simulated golf on swing mechanics and performance

• determine the effects of visual feedback on skill acquisition in beginning dance students

• the effect of repeated drop jumps on landing strategies

For more information about the Ball StateUniversity’s Biomechanics Program pleasevisit www.bsu.edu/biomechanics or contact Dr. Eric L. Dugan ateldugan@bsu.edu. n

Editors Note

Welcome to the new Vicon Standard. This first issue represents a design and content turning point in the Vicon Standard’s 15 year history. Our goal is to provide you with interesting and relevantinformation concerning motion capture technology in the Life Science market. Take this opportunity to learn how Vicon customers are using their systems and the ground-breaking discoveries they are making. This issue contains articles on the pioneering work of Dr. Richard Baker, Dr. Eric Dugan and Dr. Iwan Griffiths.

The new Standard will carry on providing you with up-to-date conference listings and Dr. Ed Biden’s literature review.

We welcome your feedback and encourageyou to contact us if you would like to contribute or be featured in our upcomingedition. Contact editorial@viconstandard.org

Emma WixeyRest of World

Tara ValgoiNorth America

/03

Vicon Setting the standard for Life Sciences

Vicon ProfilesDR. RICHARD BAKER

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/04

Richard Baker PhD CEng CSci

Director Gait CCRE/Gait Analysis Service manager

Murdoch Childrens Research InstituteRoyal Childrens HospitalParkville 3052, Victoria, Australia

Tel (+613) 9345 5354, Fax (+613) 9345 5447Email richard.baker@rch.org.au

Clinical gait analysts have recently been focusing their attention onmarker placement error – a problemwhich can arise when the reflectivemarkers are not placed in exactlythe same position on every occasion. This has been a key focus for Dr. Baker.

“Over the past 20 years many of us havebeen concerned that this might be apotential source of inconsistencies bothwithin and between different centres. Sofor example, three clinics performing thesame test on the same person may havevarying results because the placement ofthe markers doesn’t match at each clinic.Over the last five years however severalstudies have been published suggestingthat the problem, in those centres studied,is far bigger than any of us would everhave imagined.”

One of the problems is that almost allclinical laboratories are using softwaredeveloped 20 years ago and designed

for the camera technology that was available then. Dr. Baker’s work has highlighted ways to overcome this by using more markers and placing them in different positions He is also using anew generation of software incorporatingoptimisation techniques to determinewhere the bones are in relation to themarkers. These rely much less on the precise placement of the markers. Themost recent results suggest that therepeatability of measurements from thenew techniques is at least as repeatableas that of the most experienced staff using the old techniques.

Welcome to the GaitabaseOne of the reason the problem hasremained undetected for so long is thatclinical labs very rarely share data andmake comparisons. To try and solve thisissue, Dr Baker and colleague Dr OrenTirsoh have devised the Gaitabase

http://gaitabase.rch.org.au. The Gaitabaseis a pool of gait analysis related informationcontributed by clinics and research centresaround the world. The information isaccessible to anyone for analysis and comparison with other research on thesite. Information is searchable under categories such as symptoms, researchcontributor, patient age, left/right footresults, anatomical criteria and manyother categories. Early analysis of the dataon the Gaitabase has confirmed visuallythat variability of measurements can varyconsiderably between laboratories andbetween different staff in those laboratories.

Another colleague Dr Jenny McGinley has been working on methods to quantifyjust how much variability there is in dataand has developed the concept of GaitReliability Profiles to tell staff and laboratories just how well they are performing. This uses state of the art statistical techniques to produce measures which are simple and easy to interpret.

h 2__New marker set being used by Dr Baker.

h 3__New software as visualized in Polygon.

Vicon Setting the standard for Life Sciences

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The most recent step in this work hasbeen to incorporate the Gait ReliabilityProfile software into Gaitabase so thatanyone with access to the internet canupload their own data and receive a fullanalysis of how well they are performingat a simple mouse click. It is possible that this might lead to a scheme for certifying gait analysts. It certainly has the potential to allow doctors to assesswhich clinics they can trust and which they would like to disregard. In practice,this will prove invaluable to patients whosuffer with physical impairments.

There are a wide range of medical conditions that might cause someone torequire gait analysis, but physiotherapistsworking with this technology most oftenfind themselves working with children with Cerebral Palsy. This is a neurologicaldisorder that greatly affects the movementof an increasing number of children eachyear. There are currently over 17,000,000*people worldwide affected by CP. Dr. Baker explains: “As with most physical impairments each case is different, making the treatment potentially costlyand time consuming. It is essential that we can rely on the data we capture fromwhichever laboratory it is being captured

in. The main symptom of cerebral palsy is a difficulty with movement. Simplethings that most people take for granted,like climbing stairs, can be a daily struggle for some sufferers. There is no known cure, and patients are relying on gait analysis-based treatment diagnoses to help alleviate some of their impaired movement.”

Although 17,000,000 sounds a huge number across the world, any one centreonly sees a small proportion of this andsome centres see very few. Gaitabasemakes it possible for different centres toshare data and thus to allow results froma much greater number of patients to becompared. It is hoped that this will greatlyincrease our capacity to learn more aboutthis disease and how to treat it.

Dr. Baker and Vicon are thus making itpossible for surgeons and other medicalprofessionals to make more informeddecisions when it comes to their patients,thanks to the data available in theGaitabase. That can only be good news for all those people with cerebral palsy.

* www.cerebralpalsymagazine.com n

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Most experienced assessor Assessor who finds KAD placement difficult

Vicon Setting the standard for Life Sciences

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Tracking the motion of footballs in three dimensions

The lab has also recently been awarded a grant for 390K GBP over 21 months from the Knowledge Exploitation fund(Collaborative Industrial Award) to pursue a Comfort Index Research project in collaboration with the Chiropractic Clinic at the University of Glamorgan. The Viconsystem will be used to monitor humanmovement in a range of seats for automotive, aircraft, domestic and wheelchair use. A major goal of the studywill be to produce the first objectively-based measurement of seat comfort and performance. The project is beingendorsed by Magstim, Invacare, GiroflexLtd, Medical Supply System Ltd, RockwoodHospital and Huntleigh Healthcare. This is for the future, but recently the most significant work carried out is tracking the motion of footballs in three dimensions.We’ve used Vicon technology to track thetrajectory of a rapidly-moving spinningfootball. (1) Patches of reflective tape areattached to the ball at four specific locations and the ball is kicked with sidespin towards a goal. The patches occur at tetrahedrally selected positions

on the ball surface and are usually hexagonal shaped coinciding with four of the hexagons making up the football, as shown in Figure 1.

The Vicon system tracks the four markerswhich allows three dimensional position,velocity and spin characteristics to beinferred. The markers follow helical paths(Figure 2) and measuring their positionsaccurately using Vicon technology, allowsus to calculate everything we need to know about the motion of the ball. Typicalball speeds in our investigations haveranged from 22-32 m/s and ball rotationspeeds up to 60 rad/s. A procedure hasbeen developed to extract the velocity ofthe ball and the spin rate, its angle withrespect to the z axis and its angle in the x-y plane. The results so far have enabledthe deflection of the ball due to thesidespin to be accurately measured. This is what’s called the Magnus effect, namedafter Heinrich Magnus who first describedit in 1853. The Magnus effect occurs whenspinning balls tend to deflect sidewayswhen they are projected through the air

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“Skilled exponents of this banana kick such as RobertoCarlos and David Beckham have used the Magnus Effectfor direct free kicks and have demonstrated that very large ball deflections are possible.”

h Figure 2_ The four markers on the soccer ball can be tracked inside the Vicon capture volume.

h Figure 1_Soccer ball marked at four tetrahedral locations. Markers 1, 3 and 4 are “behind the ball”; marker 2 is “this side” of the ball.

The Motion Analysis laboratory at Swansea carries out sport and clinical studies usinga Vicon system. The Vicon system has been used on a number of innovative projectssuch as interlacing Vicon data with EMG data in new seating investigations and physiotherapy and weight bearing investigations.

DR IWAN GRIFFITHS, MOTION ANALYSIS LABORATORY, SCHOOL OF HUMAN SCIENCES, SWANSEA UNIVERSITY. CONTACT I.W.GRIFFITHS@SWAN.AC.UK

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Vicon Setting the standard for Life Sciences

/07and is critically dependent on the detailednature of the airflow over the ball.

Figure 3 shows that the air stream isdeflected sideways as it flows around the ball.

Conservation of momentum means that there is a Magnus force on the ball pushing it sideways as the ball movesalong. This allows footballers to exploit the curved trajectory of the ball as ameans of deceiving opposing players that the ball is going to miss the goalwhen in fact it is not. Skilled exponents of this banana kick such as Roberto Carlos and David Beckham have used the Magnus Effect for direct free kicks and have demonstrated that very largeball deflections are possible. In our work we have succeeded in measuring the lift coefficient for the football as a function of the parameter

*where d = diameter of the ball, _ = angular velocity and v = velocity of ball.

The results for the drag coefficient aresummarized in Figure 4 and are in broadagreement with our previously publishedpreliminary results. (1)

The beauty of using Vicon technology formotion tracking is that the ball is entirely

unaltered apart from the surface patchesof reflective tape used to reflect the light back to the Vicon cameras. In our work itwas found that good results were obtainedusing the four hexagonal patches providedthat the reconstruction parameters wereadjusted and optimized for a rapidly-moving and spinning object. Also, it wasfound that the radius of the ball, when calculated from the four coordinates of thepatches, gave a value about 20% smallerthan the true radius of the ball, since theVicon software was identifying the locationof the patch at a point slightly inside theball as opposed to on its surface.

Knowledge of the lift coefficient for thesoccer ball together with drag coefficientsinferred from the work of Dr. Wesson (2)

has enabled us to model the motion of theball over distances comparable with thoseused in real free kicks. In our work, we have assumed that the ball is to be kickedover a defensive wall of players 2m highand is aimed for goal at a target 2m abovethe floor. Figure 5 shows three possiblecombinations of projection angle and ball

velocity that result in the ball striking the target. In the modeling of the ball motionwe have incorporated realistic variations of the drag coefficient with ball velocityand lift coefficient with embed equationDSMT4. In the absence of spin, the stipulation of wall height and target heightconstrains the initial ball velocity and theangle of projection to a fairly narrow rangeof possible values. Modeling of the bananakick using the drag and lift coefficientsresults in a prediction of the amount ofdeflection obtainable for a given amount of spin on the ball. For example, Figure 6shows the deflection obtainable for ballangular velocities of 15, 30 and 60 rad/sfor a free kick taken at a distance of 28m.The figure shows the final position of theball in the plane of the goal posts, groundlevel is at z = 0 and the size of the goal isindicated in the y-z plane. In this case theinitial velocity of the ball was 32.2m/s andin the simulation the angular velocity vector was rotated through a complete circle in the y-z plane. This results in aslightly elliptical locus of final destinations representing various combinations of

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“The beauty of using Vicon technology for motion tracking is that the ball is entirely unaltered apart fromthe surface patches of reflective tape used to reflect thelight back to the Vicon cameras.”

sidespin and topspin. The results will be of special significance to players and coaches anxious to know how to kick the ball for best results. Based on the results of other research groups, it is now possible to specify how and where the ball should be kicked in order to specify the amount of topspin and sidespin required to produce a given balltrajectory which is on target and which has the maximum deception potential. n

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Vicon Setting the standard for Life Sciences

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; Figure 6_ The locus of final end points in the plane of the goal posts for a soccer ball kickedfrom a distance of 28m from goal for various amounts of spin on the ball. With no spin, the ball would have traveled to the point y = 0, z = 2.

References

1_Griffiths, I.W., Evans, C.J. & Griffiths, N. Tracking the flight of a spinning football in three dimensions. Measurement Science and Technology 16: 10; 2056-2065, 2005

2_Wesson, J. (2002) Football physics. Physics World, 5, 41-44

h Figure 5_ Three possible ball trajectories of a soccer ball from a free kick. (No spin)

A study in motion Principles of Biomechanics and Motion DR. GRIFFITHS’ NEW BOOK FEATURING VICON MOTION CAPTURE TECHNOLOGY.

Dr. Iwan Griffiths has been busy writing anew book offering a fresh perspective onthe basic concepts and fundamentals ofmodern motion capture. “Principles ofBiomechanics and Motion Analysis” waspublished in November 2005 and offers anew practical approach to the subject byillustrating mechanical and mathematicalprinciples with real-life examples. Thebook, published by Lippincott, Williams & Wilkins, seeks to explain the principles of mechanics and how they are applied to human movement. It does not assume that readers have a prior understanding of kinetics. This innovative text will be of particular value to students of sports science, human movement, physical therapy and sports technology and alsoallows access to electronic data so that readers can practice analysis and processing in a realistic, modern way.

The new text introduces contemporarymotion capture technology in Chapter 1and includes Vicon camera technology as part of the toolkit for motion analysis laboratories. Three-dimensional data,often obtained using Vicon, is featuredheavily throughout the book in examplesand case studies. A CD-ROM and a Web-based Resources section are available to access more data for problem-solving.

“Our studies in the Motion AnalysisLaboratory have demonstrated thatresearch into biomechanics has the potential to impact several study areas. The availability of state-of-the-art equipment has been invaluable in furthering our understanding of the subject and several case studies of theground-breaking research carried out

at the University are highlighted in thebook,” said Dr. Griffiths.

Some of the information presented in thebook has already been hailed as being'fine original work' and 'unobtainableelsewhere' by biomechanics experts.Principles of Biomechanics and MotionAnalysis will be translated into Japanesefor publication in 2007. n

Principles of Biomechanics and Motion Analysis is published by LippincottWilliams & Wilkins.Further information at www.lww.com.

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Vicon Setting the standard for Life Sciences

ConferencesNorth America

February

AMERICAN PHYSICAL THERAPY ASSOCIATIONFebruary 14-18, 2007Boston, MA*Vicon Booth #516www.apta.org

AMERICAN ASSOCIATION OF ORTHOPEDIC SURGEONSFebruary 14-16, 2007San Diego, CA*Vicon Booth #5345www.aaos.org/education/anmeet/anmeet.asp

March

VETERINARY ORTHOPEDIC SOCIETYMarch 3-10, 2007Sun Valley, IDwww.vosdvm.org

AMERICA ASSOCIATION OF HEALTH, PHYSICALEDUCATION, RECREATION AND DANCEMarch 13-17, 2007Baltimore, MDwww.aahperd.org/convention

AMERICAN ACADEMY OF ORTHOTISTS AND PROSTHETISTSMarch 21-24, 2007San Francisco, CAwww.academyannualmeeting.org/2007

April

GAIT AND CLINICAL MOVEMENT ANALYSIS ASSOCIATIONApril 11-14, 2007Springfield, MA*Vicon exhibiting and hosting the Annual User Group Meetingwww.amrinc.net/gcmas

SOUTHEAST BIOMECHANICS CONFERENCEApril 19-21, 2007Durham, NCwww.ap.gatech.edu/sebc

May

AMERICAN COLLEGE OF SPORTS MEDICINEMay 30 – June 2, 2007New Orleans, LA*Vicon exhibiting and hosting cocktail receptionwww.acsm.org

June

SOCIETY FOR EXPERIMENTAL MECHANICSCONFERENCE AND EXPOJune 3-6, 2007Springfield, MAwww.sem.org

July

INTERNATIONAL SOCIETY OF POSTURE AND GAIT RESEARCHJuly 14-18, 2007Burlington, VT*Vicon exhibitingwww.ispgr.org

August

PROGRESS IN MOTOR CONTROL VIAugust 9-12, 2007Santos, Brazilwww.demotu.org/pmcvi

INTERNATIONAL SOCIETY OF BIOMECHANICS IN SPORTSAugust 23-27, 2007 Ouero Peurto, Brazil*Vicon exhibitingwww.isbs2007.com

Rest of World

February

AUSTRALASIAN BIOMECHANICS CONFERENCEFebruary 15-17, 2007Auckland, New Zealandwww.anzsb.asn.au/abc6.htm

April

CLINICAL MOTION ANALYSIS SOCIETY – UK & IRELANDApril 2-3, 2007Birmingham, UK*Vicon exhibiting www.cmasuki.org

May

5TH STAFFORDSHIRE CONFERENCE ON CLINICAL BIOMECHANICSMay 27-28, 2007Staffordshire, UK*Vicon exhibitingwww.staffs.ac.uk/sccb

June

INTERNATIONAL CONFERENCE ON REHABILITATIVE ROBOTICSJune 13-15, 2007Noordwijk, The Netherlandswww.icorr2007.org

MATHEMATICAL MODELING IN SPORTJune 24-26, 2007Manchester, UKwww.ima.org.uk/Conferences/Maths%20Modeling%20in%20Sport.htm

8TH BIENNIAL FOOTWEAR BIOMECHANICS SYMPOSIUMJune 27-29, 2007Taipei, Taiwanhttp://fbs2007.ym.edu.tw/index.htm

July

XXI CONGRESS OF THE INTERNATIONAL SOCIETY OF BIOMECHANICSJuly 1-6, 2007Taipei, Taiwan*Vicon exhibitingwww.isb2007.org

12TH ANNUAL CONGRESS OF THE EUROPEANCOLLEGE OF SPORT SCIENCEJuly 11-14, 2007Jyväskylä, Finlandwww.jyu.fi/en/congress/ecss07*Vicon exhibiting

September

2007 ANNUAL BASES CONFERENCE(BRITISH ASSOCIATION OF SPORT AND EXERCISE SCIENCE)September 12-14, 2007Bath, UK*Vicon exhibitingwww.bases.org.uk/newsite/annualconf2007.asp

SALFORD'S 4TH INTERNATIONAL BIOMECHANICS CONFERENCESeptember 3-5, 2007-01-12Salford, UK*Vicon exhibitingwww.ihscr.salford.ac.uk/CRHPR/biomechanics2007

16TH ANNUAL MEETING OF ESMACSeptember 24-29, 2007Athens, Greece*Vicon exhibitingwww.esmac.org

/09

‘Foot and ankle kinematics and groundreaction forces during ambulation’, FootAnkle Int. 2006 Oct;27(10):808-13. KitaokaH, Crevoisier XM, Hansen D, Katajarvi B,Harbst K, Kaufman K.,

The authors acknowledge the challengesof measuring motion in the foot and makethe point that most gait analysis has treated the foot as a single rigid segment.They present data for 20 normal subjectsbased on a three-segment model usingeleven markers to track relative motionswithin the foot. Their objective is to establish a normal standard for suchmotions. They document motions in threeplanes between the calf and the hind footand the mid-foot. To provide coherencewith more conventional measures, theylink their data to measures of groundreaction force, and time distance measures.The difficulty in this sort of approach isthat the measured motions are likely to behighly correlated with the model chosenand with the marker set which is applied.

More interesting still, in that they providenorms and comparisons is Tome, J.,Nawoczenski, D., Flemister, A., Houck, J.,‘Comparison of Foot Kinematics BetweenSubjects With Posterior Tibialis TendonDysfunction and Healthy Controls’,Journal of Orthopedic and Sports PhysicalTherapy, 2006 Vol.36 No.9, pp 635-644.

They present a complex foot model withfive segments including tibia, rear foot,midfoot forefoot and hallux to compare 14people with posterior tibialis dysfunctionto a group of 10 normal controls. Theircontrols were age, gender and body mass index matched to the test group. Asa result, their information is somewhat less generic than that of the previouspaper but more readily interpreted. Intheir measurements they use a triad ofthree markers per segment, which allows determination of independent coordinatesystems for each. Their comparisons with normal, involve measures of theinter-segmental motions across the foot.They find that for the population testedthere were systematic differences at each articulation. On the basis of this they make suggestions as to appropriate therapy to address this condition.

The authors present In a somewhat similarstudy, the authors, Khazzam M, Long J.,Marks R., Harris G.,’ Kinematic changes of the foot and ankle in patients with systemic rheumatoid arthritis and forefoot deformity’, Journal OrthopedicResearch. 2006 Dec 1; draw on a group of22 adults with rheumatoid arthritis and acontrol group of 25 using a four segmentmodel. Their results showed significant differences between the two groups foroverall gait parameters as well as for the

relative motion of their defined segmentswithin the foot. They suggest that understanding of the details of the inter-segmental motions within the footcan lead to improved treatment planning by being able to be more specific as towhich muscles, ligaments, etc. are likely to be involved directly.

The last paper reviewed regarding footmodels is by Galois L, Girard D, MartinetN, Delagoutte JP, Mainard D,“Optoelectronic gait analysis aftermetatarsophalangeal arthrodesis of thehallux: fifteen cases”, Rev Chir OrthopReparatrice Appar Mot. 2006 Feb;92(1):

Literature Update for The Standard DR. ED BIDEN

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Vicon Setting the standard for Life Sciences

”They suggest that understanding of thedetails of the inter-segmental motions within the foot can lead to improved treatment planning by being able to be more specific as to which muscles, ligaments, etc. are likely to be involved directly.”

It has been well over 25 years since I first saw a computer-based motion capturesystem in fact; it was an original Vicon system. At that time gait assessment waschallenging to say the least. The idea of being able to capture movement data of thefoot, treated as a multi-segment structure, seemed next to impossible. As I beganto collect literature for this Update it became clear that foot mechanics is now wellwithin reach.

52-9. Their results are interesting in thatthey studied patients after arthrodesis and found that there was little change inthe overall gait parameters because thepeople tested were able to compensate by movements within the foot itself. Theyfound that the interphalangeal joint wasproviding the adaptation needed to compensate for the arthrodesis in order to leave the whole leg motion measuresunchanged. This is a strong argument formulti segmental foot models because itillustrates that they have the potential todetect pathology and guide treatment even when whole limb models define themotions as normal. This seems to be anarea where consistency in approach tomodeling is going to be critical if there isany hope of comparing across studies todraw broad conclusions.

Upper LimbAnother area, which is increasingly beingassessed using motion analysis, is that ofthe upper limb. Generally arm motions areless cyclic than gait, which poses specificchallenges. This is particularly true forconditions such as Cerebral Palsy, whichaffect coordination. Sanger, T, ‘Arm trajectories in dyskinetic cerebral palsyhave increased random variability.’,Journal Child Neurology. 2006Jul;21(7):551-7 approaches this problem in a unique way. He compares 7 childrenwho are between the ages of 4 and 13 and have Cerebral Palsy (CP) with a control group of 21 unaffected children in approximately the same age range. Themeasured task was outward reaching, andthe measurement to assess consistencywas to fit the pattern of reaching and then use this fitted curve compared to the actual motion to define a “signal tonoise” ratio where the fitted curve is takenas the “signal” and deviations from it represent the noise. Not surprisingly thechildren with CP had significantly reduced“signal to noise” ratios, which the authorthen speculates may be due to the children being unable to filter their controlling signals properly. This approach gives a straightforward way to model variability in non-cyclic motions. Upper limb measurements also extend to assessment of high performance sport.

Roca M, Elliott B, Alderson J, FosterD,’The relationship between shoulderalignment and elbow joint angle in cricketfast-medium bowlers’, Journal SportsScience. 2006Nov. 24(11):1127-35 studyhigh performance cricketers measuringshoulder alignment and elbow angles toassess whether the players are likely toexceed International standards for elbowtolerance. They conclude that variations in style are likely to put some athletes

at risk and recommend particular trunk orientations during the pitching motion to minimize the effect. This is a good example of the use of motion analysis to enhance the qualitative information, which coaches or clinicians can obtain by visual observation.

The last paper is by Barker S, Craik R,Freedman W, Herrmann N, Hillstrom H'Accuracy, reliability, and validity of a spatiotemporal gait analysis system’, Med Eng Phys. 2006 Jun;28(5):460-7.

It illustrates that Vicon is truly “the standard”. The authors examine a simplemat based system for motion analysis. Itconsists of an array of switches that coverthe mat surface and allow detection oftime distance parameters by using a computer to monitor the state of theswitches continuously. Their benchmarkfor measurement was a Vicon system that they describe as the “Gold Standard

for motion analysis”. They found that themat system was very comparable in termsof timing measures but that it had somedifficulty in measures of distance due primarily to the fact that the switch locations were not completely consistent.They conclude that the differences weresmall enough that the errors would beunlikely to affect clinical decision-making. The advancement of motion analysis continues to fascinate me. The very

broad range of motions that pique people’s interests seems to be ever expanding.

Best wishes for the New Year,

Ed BidenUniversity of New BrunswickCanada n

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Vicon Setting the standard for Life Sciences

IT ILLUSTRATES THAT VICON IS TRULY “THE STANDARD”. THE AUTHORS EXAMINE A SIMPLEMAT BASED SYSTEM FOR MOTION ANALYSIS. IT CONSISTS OF AN ARRAY OF SWITCHES THAT COVER THE MAT SURFACE AND ALLOWDETECTION OF TIME DISTANCE PARAMETERS BY USING A COMPUTER TO MONITOR THE STATE OF THE SWITCHES CONTINUOUSLY. THEIR BENCHMARK FOR MEASUREMENT WAS A VICONSYSTEM THAT THEY DESCRIBE AS THE “GOLDSTANDARD FOR MOTION ANALYSIS”.

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Vicon Annual Users Group Meeting

VICON WILL BE HOSTING ITS ANNUAL USERSGROUP MEETING AND SUPPORT SESSIONS DURING THE 12TH ANNUAL GAIT AND CLINICALMOVEMENT ANALYSIS SOCIETY MEETINGAT THE SHERATON SPRINGFIELD MONARCH PLACE, SPRINGFIELD, MAAPRIL 11-14, 2007

Support+Service Sessions

Vicon Support+Services will be offering 45 minute One-on-One sessions that will allow users to focus on specific topics with a dedicated Support Engineer. Take this opportunity to ask all of the technical support questions you’ve been meaning to call about and find out more about our newly developed service and support plans. Time slots will be available on the hour between 8:00 AM and 5:00 PM Wednesdaythrough Friday excluding lunch breaks. To reserve the time slot of your choice, please RSVP to dudley.tabakin@vicon.com with a summary of your question and your preferred time.

User Group Event

HIGHLAND BALLROOMTHURSDAY, APRIL 12TH - 7PMJoin us and your colleagues for an entertaining evening with dinner and drinks while you experience what’s new at Vicon. Try out our latest software, Vicon Nexus or get your hands on a new MX40+ camera to see what makes Vicon technology truly revolutionary.

Please RSVP to gcmasusergroup@Vicon.com to secure a spot for each member of your group attending this event.

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