1 | P a g e

M e mo ra ndu m : D at e : 1 0/2 3/ 2 0 1 2 F ro m : Cl iv e D ’ S o uz a a n d E d ward Stei n fel d , I D eA Cen te r, Un i v e rsity at Buffa l o To : R e x P ace, Te ch n ical As s ista n ce Co o rd i n at o r, U.S. Acc e ss B o ard

**RE: A**  **nal y** **s i**  **s o** **f Tr** **an sf** **e r**  **Su r** **f a**  **c e**  **D i**  **me n**  **s i**  **on s**  **B a**  **s e**  **d o**  **n W**  **hee l**  **e d**  **M o**  **b ili**  **t y**  **U s**  **e r**  **Ant h**  **r opo**  **metry**
**Su mm**  **a r** **y** The fo ll o wing re p o rt p rov i d es a br i ef ana l ysis o f fo u r a n thro po m etric d i m ens i o n s which w e re c o n si d e red relev a n t to t h e width and depth di m ensions o f a s e a t i n g surfa ce fo r w h e e led mob ility d ev ice u s ers. T h e d a t a are based o n fi nd i ngs fro m the A n thro po m et ry o f Wh e eled M o b ili ty ( AW M ) P roj e ct, a n d co m p rises o f d et ai l ed st atic m e as u re m e n ts c o l l ect ed fro m 5 0 0 u se rs o f m a nu al whe e l ch a irs, po wer w h e e lc h ai rs a n d sc o ot e rs. This a n alysis fo cu s es o n ly o n t h e a d eq u a cy o f t h e pro po sed tra n sfer su rface d i m e n si o n s as a st a tic sea t i n g su rface
– i.e., n o m easu re m ents o f t ra n sfe rs were re c o rd ed. T h e p ro po s ed d im ensions fo r tra n sfer su rface 30 i n . wi d e a n d 1 5 i n . d e ep i s e st i m a ted t o be ade qu ate as m i n i m u m cri t eria fo r a static sea t i n g surfa c e. Our res e arch fi nd i ngs d e m o n st rate t h a t the m i n i m u m w i d t h o f t h e su rfa ce c o u ld be a s s m all as 2 8 in. and still acc om mo d a te 9 5 % o f o u r sa m p le. It sh o u ld be n ot ed t h at Add iti o n al width m ay be req u ired fo r acc om mo d a ti n g users that are mo r b i d ly o b ese o r u s e b ar i atric w h e e lc h ai rs. F u rt h er m o re, ad d iti o n al sp a ce m ay be n e eded to a c c o mm o d ate t h e task o f tra n sferr i ng, depe nd i n g o n t h e ad d i t i o n al fe a tures p rov i d ed, e . g . ar m re sts o r rai l i ngs. U s er test i n g is reco m m en d ed fo r ar r iving at m o re accu ra te t ra n sfer s u rfa ce d i m ensions a n d desi g n fe atu re s t o ins u re u sa b ility fo r a b road dive rsity o f u sers, i n cl ud i n g in d ivid u als with m o b ility i m p ai rm ents.2 | P a g e

**I n** **t r** **odu c** **t i**  **o n**  The p ro p o sed g u i d eli n es fo r m ed i cal d i a gn o st i c eq u i p m ent re co m m en d s a m i n i m u m t ra n sfer surfa c e 3 0 i n . ( 7 60 m m ) wide and 1 5 in. ( 3 8 1 m m ) de e p . At t h e re q u est o f t h e U. S
. A c c ess B o a rd st aff, a br i ef a n al ysis was p erfo r m ed b a s ed o n st at i c a n thro po m etry m easure m ents p rev i o u s l y c o ll e ct e d to ev al u a te t h e a d eq u a cy o f these tra n sfer su rface d i m ensions. The Cen t er fo r I n cl u s i ve D e si g n and E n v iro n m e n tal Acce s s ( I D eA) at the Un i v e r s i ty at B u ffa l o c o ndu cted an a n thro po m etric stu d y o f 5 00 in d i v i du als w h o use w h e e led m o b ility d e v i c es (W MD ) 1

. The res e a rch i n cl ud e d the c o lle cti o n o f d e m og ra p h ic i n fo r m at i o n and W M D ch a racteri stics, a n d the m e as u re m ent o f st r u ctural a n d fun cti o n al a n th ro po m etry . D ata c o l l ect i o n inc lud ed 3 d i m ens i o n al m easure m en ts o f ap p rox i m a t ely 9 0 p o i n ts l o ca t ed o n the b o d y and d ev ice. L i n ear di stances be twe e n pa i rs o f m e a su red poi nts can be c om pu t ed to p rov i d e di m ensional est i m at e s o f b o d y and m o b ility de v i c e si z es. Fo u r st a tic b o d y d i m ens i o n s c o n si d e red re l e v a nt t o t h e width and d e pth d im ens i o n s o f a sea t i n g surfa c e we re c o m pu t e d and ana l yz ed t o serv e as a re ference. T h e s e dim e n s i o n s incl ud e : t h i g h b rea d th, sho u l d er brea d th, bu tto c k

- p o p lit e al len gth, a n d w h e e lc h air seat dept h
. D i m ension val u es are st rat ified by gen d er and mo b ili ty de v ice ty p e si n c e si gn ifi ca nt d ifferen c es in size and s pace req u ire m ents e x ist ac ro ss these su b

-g ro up s. A l l d i m ens i o n s are based o n o ccu p a n t stat i c po stures w h i le s e a t e d in t h eir own m o b ility d ev ice. As suc h , the a n alysis fo cuses o n l y o n t h e a d eq u acy o f t h e p ro p o s e d t ra n sfer s u rfa ce d i m ens i on s fo r a st at i c s e ati n g su rfac e . N o m easure m e n ts o f t ra n sferri n g to o r fro m t h e m o b ility d ev ice w e re re c o rd ed. Hen ce, the d i m ens i o n s disc u ssed in th i s re p o rt s h o u ld o n ly b e co n si d ered as a st a rti n g p o i n t fo r a c cessi b le d e si g n o f a sea t i n g surfa c e . When d et e r m i n i n g space req u ire m en ts fo r d y n a m i c tra n sfer t a s ks, t h ere are ad d iti o n al s p a c e n e e d s and fu n ct i o n al a b ilit i es o f t h e user p o pu lati o n w h ich m u st b e c o n si d ered. F o r ex a m p le, in d ivid u als m a y n e e d ad d iti o n al space to po sit i o n t h eir ha nd s w h en co ndu cting a si d e t ra n sfer. Issues o f co m fo rt a n d s e cu r ity n e e d to be c o n si d e red. Ta s ks that are perfo r m ed o n t h e tab l e, l i ke ro lli n g ov er, n e e d to be ac co m m o d a t ed. F u rther m o re, t h e qu e sti o n o f h ow to ac c o mm o d ate m o r b i d ly o b ese in d iv i du als st ill needs to be ad d res s ed. The ch a rts be l ow w e re d evel o p ed us in g a st at i stical a n alysis packa ge w ith s o m e bu il t - in fe atu res. The re a d e r will n ot i ce d a t a p o i n ts n ot e d as “e xt re m e v al u es . ” T h e statisti c al p acka ge a n alys es t h e d ata to ide n ti f y “o u tl i ers, ” o r v al u es that exce e d e x p e ct e d v al u es in d a ta with a n o r m al d i stri bu ti on . It t h en i n cl ud es t h o se v al u es in the gra ph ics as o u tside t h e ran ge of m ax i m u m and m i n i m u m v al u es in each d i stri bu t i on . The ch a rts serv e as a v is u al aid fo r u nd erst a nd i n g h o w t h e d iv ers ity o r sp re ad in m easure m e n t v al u es w it h in and b etwe en e a ch o f t h e six s u b

-g ro up s of d e v i c e u se rs t h at were stu d ie d
. H o we v e r, t h e “ e xt re m e v a l u es” a re i n cl ud ed in o u r a s ses s m ent and re co m m en d at io n s o n a c c om mo d a ti n g 9 5 % o f t h e s a m p le, si n c e t h ese “ ext re m e v al u es” rep re sent g en u i n e cases o f in d iv i du als (as o pp o sed to e r ro rs in m easu re m ent) that n e ed t o b e a c c om mo d a t e d by d esign and hence should n ot be e xcl ud ed fro m t h e a n alysis, an d , t h e d i m ens i on s that we ana l yz ed were n ot n o r m al d istri bu t e d d u e to a b ro ad di versi ty in t h e o b se rv ed m e a su re m ents. H ence t h e p erc entiles w e re c o m pu t e d separa t ely b a se d o n t h e o b s erved d a ta a n d n ot a n i m p lied n o r m al d ist r i bu ti o n . Reade rs can a ssu m e that these “e xt re m e v al u e s” repre s ent u nu su a lly la rg e o r sm a ll di m ensions fo r t h e p o pu lat i o n st ud ied t h at m i gh t n e e d s p ecial a cco mm o d at i o n t h ro ug h desi g n a nd /o r so m e ty pe o f person al assista n c e .
1 Ste i n fe l d , E ., P a qu et, V., D'So u z a , C., Jo se ph , C., Mai s e l, J ., 2010. Fi n al R e p ort: A n t h r op o metry of Whe e l e d Mo b ility Proje ct. P re p are d for t h e U
. S. Acc e s s Bo a rd
. ID eA C e n ter, B u ffal o , N Y
.3 | P a g e

**1 .**  **T hi**  **g h**  **Br ead**  **th** Thi g h brea d th was used to p rov i d e an e sti m a te o f the width o f t h e sea t i n g surfa ce. T h i g h brea d th fo r t h is a n alysis w as co m pu t e d as t h e la rger o f two di m ensio n s, t h e h o ri z o n tal dista n c e betwe e n t h e la t eral ( o u t e r) as p ect o f the hi p s, and the h o ri z o n tal d i stance b e twe e n t h e la t eral as p e cts o f the th igh s, w h en sea t ed in the whe e lc h air a n d n ot c o n si d eri n g any whe e lc h air hard ware. Fi gu re 1 p rov i d e s a b ox - p l ot s h o wing t h e d istri bu ti o n fo r t h i g h brea dth stratifi ed by gen d er a n d mo b ili ty d ev i c e ty p e. It sh o u ld be n oted that the th ig h b rea d th d im ension fo r m a n u al a n d p o wer w h e e lc h air u sers m ay b e und ere sti m a ted d u e to la t eral po sture su p p o rt fe a tures (such as d o ub l e - p o st a r m re st, w h e e l ch a ir si d e gu ard ). S c o ot e rs general l y h a v e si ng le p o st armre sts a n d he n ce t h e o ccu p a n ts’ th igh s are lat e ral l y “ un su pp o rt e d ” and t end to be w i d er r efl e cting a mo re n atu ral p o stu re. In w h e el c h ai rs, t h e a r m rest s a n d side g u ard s c o u ld c o m p re ss o v erall b readth o f t h e th igh s t o a c e rtain e xt ent. I n a d eq u ate s e a t wi d th can b e m o re pro b l e m at i c fo r i n d ivid u als that h a ve b ro a d er hi p s an d /o r t h i gh s. As suc h , t h e width d i m ens i o n s h o u l d be b ased o n t h e hi gh er e n d o f t h e s a m p le distri bu t i o n to p rov i d e a su ffic i ent b ase o f su pp o rt fo r as large a p ro p o rt i o n o f t h e u ser p o pu l ati o n as p o ssi b l e (e. g ., 9 5 t h o r 99 t h p erc e n til e ). T h e 9 5 th p erc e n tile a n d m a x i m u m val u es ac ro ss the 6 sub

-g ro u p s w e re w i th i n a ra ng e o f 2 2 i n - 28 i n , and t h e m a xi m u m v al u es w e re w i th i n t h e 26 i n - 30 in. ra ng e. A m i n i m u m width o f 3 0 in wo u ld the re fo re ens u re that all i nd i v i du als o f o u r s a m p le wo u ld be ac co mm o d at e d in t e r m s o f t h e width o f a st a t i c s e ati n g s u rface. If the m i n i m u m width were red u ced to 2 8 i n . o n ly th ree in d i v i du als in o u r s a m p le wo u ld n ot b e a ccom mo d a t e d
.

**F ig**  **ur e**  **1** : Bo x - p lot sh o w i n g t h e d i stri bu ti o n for t h igh b re a d th stratifie d b y gen d e r a n d m o b ility d ev ice typ e . T h e h oriz on t a l li n e splitt i n g th e b ox d e p icts th e m e d ia n , th e b ox l e n gth re p re se n ts th e i n t e r - q u artile (25th
– 7 5th p e rc e n ti l e ) ra n g e, an d th e w h i s ke r s re p r e se n t t h e min i m u m an d max i mu m val ue s . E xtre m e val u e s a r e sh o w n a s d ots an d a st e ri s k s . T h e re d d ott e d li ne s d e p ict th e ob se rve d ra n ge o f 9 5 th p e rc e n tile val u e s a cr o s s s u b

- gro u p s .4 | P a g e

**2 .**  **Shou l**  **de r**  **Br ead**  **th** S h o u l d er b rea d th t e nd s t o b e sli gh tly g rea t er t h an hip o r t h i g h brea d th and hence w as u s ed as a n est i m a t e fo r the w i d th o f an ex a m i n at i o n t a b le w h en in a recli n ed p o sit i o n . S h o u l d er b re a d th was co m pu t e d as t h e h o ri z o n tal d i stance b etwe e n t h e la t eral ( o u t e r) as p e cts o f the de l t o i d s. F igu re 2 p rov i d e s a bo x - p l ot s h owing the distri bu t i o n fo r sh o u l d er brea d th stratified by g e n d er a n d m o b ili ty d ev ice ty p e. I n a d eq u ate s e a t wi d th can b e m o re pro b l e m at i c fo r i n d ivid u als that h a ve b ro a d er sh o u l d ers a n d/o r are o b ese. As s u ch, the w i d th d i m ens i o n sh o u ld b e b ased o n t h e h i gh er end o f the s a m p le d i stri bu ti o n to p rov i d e a su fficient base o f su pp o rt fo r as l arge a p ro po rti o n o f the user p o pu lat i o n as p o s s i b le ( e. g . 9 5 t h o r 99 th p erc e n til e ). The 9 5 t h p erc e n tile v al u es a cro ss t h e 6 s u b

-g ro up s ran g ed fro m 2 3
- 27 .5 in
. , and t h e m a x i m u m v al u es ra ng ed fro m 2 5
-3 4 i n . A m i n i m u m width o f 30 i n . wo u ld e n su re that all i n d ivid u als o f o u r sa m p l e wo u l d b e ac c o mm o d a ted in t e r m s o f static b o d y w i d th. H o wev e r, spa ce fo r t a s ks such a s t u r n i n g o ver to t h e si d e when recli n i n g is n ot bei n g c o n si d ered. A wi d er e xa m i n at i o n t a b le (i. e ., g rea ter than 30 i n .) m a y be n e eded if ac c o mm o d a ti n g in d ivid u als that a re mo r b i d l y o b ese an d/o r use bar i atric whe e lc h ai rs is al so a p r i o ri ty . Our stu d y s a mp le is not rep res e n t a ti v e in t e r m s o f t h e bar i atric wh ee lc h air user p o pu lati o n – i
. e . , w e h ad o n l y o n e b ar i atric whe e lc h air u ser in the sa m p le alt h o ug h we did h a v e m a n y p e o p le who w e re qu ite o b e s e . T h e o u tlier v a l u es ac ro ss th ig h brea d th a n d shoul d er b rea d th m i gh t s e rv e as a refe ren ce fo r d et e r m i n i n g t h e n e eds o f m o r b i d ly o b e se i nd ivid u als w h o u se whe e led m o b ility d ev ices ( e. g ., 3 4 in
. ).

**F ig**  **ur e**  **2:** Box
- p lot s h o w i n g t h e d i stri bu ti o n for s h o u l d e r b r e a d th stratifie d b y gen d e r a n d mo b ility d ev i c e typ e . T h e h oriz on t a l line s p litti n g th e b ox d e p icts th e m e d ia n , th e b ox l e n gth re p re se n ts th e i n t e r - q u artile (25th
– 7 5th p e rc e n ti l e ) ra n g e, an d th e w h i s ke r s re p r e se n t t h e min i m u m an d max i mu m val ue s . E xtre m e val u e s a r e sh o w n a s d ots an d a st e ri s k s . T h e re d d ott e d li ne s d e p ict t h e ob se rve d ra n ge o f 9 5 th p e r c e n tile val u e s a cr o s s s u b

- gro u p s .5 | P a g e

**3 .**  **B u** **tt o** **c k** **- P**  **op l**  **i te**  **a l**  **L en**  **gt h**  For t h is stu d y, an e st i m a te o f b u tt o c k

- p o p lit e al len gth was calc u l a t e d as t h e h o ri zo n tal d i sta n ce fro m t h e p ro x i m al ( rear) ed ge o f t h e whe e lc h air seat c u sh i o n to the p o p li teal fo ssa (i.e., c re ase at t h e b a c k o f t h e kn ee ) o f t h e ri gh t leg. The m ed i a n b u tto c k

- p o p lit e al le ngth p rov i d es an u pp er b o un d fo r t h e depth o f a s e ati n g su rface. If s eat de pth is i n c reased b eyo n d t h is len gth, it be c o m es d iffic u lt to e nga g e the ba c kre st as w e ll as e x erting p ressure to t h e b a ck of t h e k n e es. Fi gu re 3 p rov i d e s a bo x - p l ot s h o wing t h e d istri bu ti o n fo r shoul de r b rea d th stratifi ed by gen d e r and m o b ility de v i ce ty p e. The m ed i an ( 5 0 t h p erc e n ti l e) val u es fo r bu tto c k

- p o p lit e al len gth a c ro ss the 6 sub

-g ro up s ran ged fro m 18
. 5
- 1 9 .5 i n . Seat d epths should prefera b ly n ot e x c e ed the s e v al u es (s e e n e xt s ect i o n fo r mo re i n fo r m at i o n ).

**F ig**  **ur e**  **3:** Box
- p lot s h o w i n g t h e d i stri bu t ion for a pp ro xi m a t e bu tt oc k

- p o p liteal l e n gth stratifie d b y gen d e r a n d mo b ility d ev i c e typ e . T h e h oriz on t a l li n e splitt i n g th e b ox d e p icts th e me d ia n , th e b ox l e n gth re p r e s e n ts th e i n te r - qu arti l e (25th
– 75th p e rc e n til e ) r an g e, an d th e w h i s k e rs r e p re se n t t h e min i m u m an d maxim u m val u es . E xtre m e val ue s a re s h o w n a s d ots an d a steri s k s . T h e r e d d ott e d li n e s d e p ict th e obs e rve d ra n ge of 9 5 th p e rc e n ti l e val u e s a cro s s su b

-gro up s . **4 .**  **Whee lc**  **hai r**  **s ea** **t dep** **th** For t h is stu d y, whe e l ch a ir seat depth w as calc u la t ed a s t h e h o ri z o n tal dista n ce fro m t h e p ro x i m al (i.e., t o ward s t h e re ar) e dge to t h e d istal (i.e., t o wards t h e fo rward ) e dg e o f the whe e l ch a ir seat c u sh i o n . I nd ivid u al whe e lc h air seat dept h s a re genera l ly a b o u t 2 in. l ess t h an b u tto c k

- p o p lit e al len gt h in m o st case – th i s is a ro ug h g u i d eli n e a n d is qu i te s i m ilar to d e ci d i n g s e at d epths fo r a m bu lat o ry in d iv i du als e. g ., fo r o ffi c e ch a irs. The m ed i an seat de pth ac ro ss diffe rent whe e l ed mo b i lity d ev ic e s w o u ld p r o v i d e a refe rence v al u e fo r the d epth o f ot h er co m m o n se ati n g surfa ce s . F igu re 4 p rov i d es a b ox - p l ot s h o wing the distri bu ti o n fo r wh e elch a ir seat de pth stra tified by ge n d er a n d m o b ili ty d ev ice ty pe. The m ed i an ( 5 0 t h p erc e n ti l e) val u es fo r whe e lc h air s e at d epth ac ro ss t h e 6 sub

-g ro up s ran ged fro m 1 4
- 1 7 i n . The p ro p o sed g u i d eli n es re c o m m end a t ra n sfer s u rfa ce d epth o f 15 i n . which is at abo u t the m i dd le o f t h is ra ng e a n d m a y be ap p ro p r i at e .6 | P a g e

**F ig**  **ur e**  **4:** Box
- p lot s h o w i n g t h e d i stri bu ti o n for a pp ro xi m a t e w h ee l c h air se at d e p th strat i fi e d b y gen d e r a n d mo b ility d ev i c e typ e . T h e h oriz on t a l li n e splitt i n g th e b ox d e p icts th e me d ia n , th e b ox l e n gth re p r e s e n ts th e i n te r - qu arti l e (25th
– 75th p e rc e nt il e ) r an g e, an d th e w h i s k e rs r e p re se n t t h e min i m u m an d maxim u m val u es . E xtre m e val ue s a re s h o w n a s d ots an d a steri s k s . T h e r e d d ott e d li n e s d e p ict th e obs e rve d ra n ge of 9 5 th p e rc e n ti l e val u e s a cro s s su b

-gro up s . **C on**  **cl u**  **s i**  **on s**  The p ro p o sed g u i d eli n es fo r m ed i cal d i a gn o st i c eq u i p m ent c u rre n t l y re c om m e n d a m i n i m u m t ra n sfer surfa ce 3 0 in. (7 6 0 m m ) wide and 1 5 in. ( 38 1 m m ) de e p . Our fi nd i ngs su pp o rt th o se d i m e n si o n s b u t al so su gg e st th a t the w i d th c o u ld be re du c e d t o 2 8 in. Our ana l ysis ba sed o n static ant h ro p o m et ry m easure m ent s . It fo cu ses s o le l y o n t h e a d eq u acy o f t h ese t ra n sfer su rfa ce d i m e n si o n s fo r a static s e ati n g s u rfac e . N o stu d ies o r m easu re m ent o f t ra n sfers w e re re c o rd ed n o r d i d w e c o lle ct i n fo r m a ti o n o n t h e sp a ce n e eds o f other tas ks o n e x a m t a b l e s l i ke re p o sit i o n i n g t h e b o d y fo r exa m s . Based o n an a n th ro po m et r ic an a lysis o f fo u r rel ev a n t d i m ens i o n s, w e h a v e the fo ll o wing o b se rv at i o n s and recom m en d at i o n s: 1
. The pro p o sed m i n i m u m tra n sfer s u rfa c e width o f 3 0 in. prov i d es su fficient sp a ce as a st a t ic s ea t i n g su rface fo r a l m o st all in d iv i du als in o u r s a m p le o f wh e eled mo b ili ty use rs based o n st atic m easu re m ents o f h i p and t h i g h brea d th. This width c ou ld be red u ced to 2 8 in. a n d st ill ac co m m o d a te 9 5 % o f o u r s a m p le. 2
. A width o f 3 0 in. wo u ld a lso a c co m mo d a te the s h o u l d er b rea d th o f m o st i nd iv i du als should t h is b e req u ire d , e . g ., when the t a b le is in a recli n ed p o sit i o n . Red u ci n g t h is width t o 2 8 i n . wo u ld st ill acc om mo d a te 9 5 % o f o u r sa m p le. 3
. I n cre a si n g t h e m i n i m u m width is re c om m en d ed if a ccom mo d a t i n g in d ivid u als that are m o r b i d ly o b e s e a nd /o r u s e b ar i atr i c wh e e l ch a irs is al s o a p r i o ri ty . The m ax i m u m v al u es re c o rd ed fo r th ig h brea d th a n d sh o u l d er b rea d th s e rv es as a re ference v al u e sh o u ld ac c om mo d a ti o n s fo r t h ese u s ers b e n ec e ssa ry . 4
. A d e pth o f 1 5 i n . fo r a s e ati n g surfa ce was fo un d to b e su i tab l e b a s ed o n m ed i a n v al u es o f bu tto c k

- p o p lit e al len gth a n d w h e e lc h air s e at dept h s.7 | P a g e

5
. Th e se results refle ct st at ic ant h ro po m et ry m easu re m ents and sh o u ld b e c o n s i d ered as a st arti n g p o i n t fo r a c ce s si b le design o f a sea t i n g surfa ce. Us e r t e sti n g is re com m en d ed fo r arr i v i n g at m o re ac c u ra te tra n sfer s u rfa c e d i m ens i o n s and desi g n fe a tures to in s u re u sa b ility fo r a broad d i versi ty o f u s ers a n d the full ran ge o f tas ks t h at m i gh t t a ke pl a ce o n an ex a m t a b l e .