a checklist for evaluating ergonomic risk factors resulting_2

8/12/2019 A Checklist for Evaluating Ergonomic Risk Factors Resulting_2

1/19


2/19

284 W M Keyserling et al / Checklist fo r evaluating ergonomic risk factorsT a b l e 1A d v e r s e h e a l t h e f f e c t s a ss o c i a t e d w i t h v a ri o u s p o s t u r e s .P o s t u r e A d v e r s e h e a l t h e f f ec t s R e f e r e n c eS t a n d i n g s t a t i o n a r yU s i n g a f o o t p e d a lK n e e l i n g

S q u a t t i n gS i t ti n g w / b a c k s u p p o r tS i t t in g w / o b a c k s u p p o r tM i l d f l e x i o n / t r u n k

S e v e re f l e x i o n / t r u n k

T w i s t e d / b e n t / t r u n k

M i l d f l e x i o n / n e c kS e v e r e f l e x i o n / n e c k

T w i s t / b e n t / n e c k

E x t e n s i o n / n e c k

C o m p r e s s i o n n e u r o p a t h i e sP a i n i n t h e l o w b a c k , h i p a n d k n e eI n c r e a s e d h e a r t r a t e a n d o x y g en c o n s u m p t i o nC o m p r e s s i o n n e u r o p a t h i e sC o m p r e s s i o n n e u r o p a t h i e sC o m p r e s s i o n n e u r o p a t h i e sL o w b a c k p a i nI n c r e a s e d h e a r t r a t e a n d o x y g e n c o n s u m p t i o nB a c k p a i n

I n c r e a s e d h e a r t r a t e a n d o x y g e n c o n s u m p t i o nB a c k p a i n

B a c k p a i n

N e c k p a i n a n d s t i f fn e s sP a i n i n t h e n e c k , u p p e r b a c k a n d a r m sN e c k p a i n a n d s t i f f n e s sN e c k a n d s h o u l d e r p a i nH e a d a c h eN e c k p a i n

F e l d m a n e t a l . , 1 9 8 3Cor le t t e t a l . , 1976Sa to e t a l . , 1973F e l d m a n e t a l . , 1 9 8 3F e l d m a n e t a l . , 1 9 8 3F e l d m a n e t a l . , 1 9 8 3G r a n d j e a n e t a l . , 1 9 8 3Sa to e t a l . , 1973P u n n e t t e t a l . , 1 9 9 1A n d e r s s o n , 1 98 1Sa to e t a l . , 1973P u n n e t t e t a l . , 1 9 9 1A n d e r s s o n , 1 9 81P u n n e t t e t a l . , 1 9 9 1A n d e r s s o n , 1 98 1G r a n d j e a n e t a l . , 1 9 8 3H a r m s - R i n g d a h l e t a l ., 1 9 86 bG r a n d j e a n e t a l . , 1 9 8 3To la e t a l . , 1988Trave l l , 1967Trave l l , 1967

T a b l e 2P e r c e n t a g e o f w o r k e r s w h o r e p o r t e d p a i n i n v a ri o u s a r e a s o f t h e b o d y o v e r v a r i o u s t i m e p e r i o d s .O c c u p a t i o n N e c k B a c k H i p T h i g h s K n e e C a l f A n k l e F e e t T i m e R e f e r e n c eB u t c h e r 2 7 5 5 9 2 6 2 0 3 m o n M a g n u s s o n e t a l . , 1 9 87M e l t e r s 2 0 3 4 2 8 4 2 3 0 1 d a y P a l u c h , 1 98 9M old e rs 10 26 20 32 24 1 day Pa l uch , 1989M a i n t e n a n c e w o r k e r s 1 1 2 0 2 2 3 8 2 2 1 d a y P a l u c h , 1 98 9A i r c r a f t l o a d e r s 1 8 2 7 1 0 t ) 3 5 6 f ) 7 d a y S t a l h a m m a r e t a l ., 1 9 86A i r c r a f t l o a d e r s 3 8 6 3 2 4 t ) 6 3 2 0 f ) 1 y r S t a l h a m m a r e t a l ., 1 9 86F i s h e r m e n 1 9 5 2 1 3 2 5 1 1 1 y r T o r n e r e t a l ., 1 9 88S l a u g h t e r h o u s e w o r k e r s 4 9 s ) 4 2 1 y r V i i k a r i - J u n t u r a , 1 9 83E l e c t r o n i c s a s s e m b l y 6 4 1 1 1 0 1 2 4 a ) W e s t g a a r d e t a l ., 1 9 84C a b l e m a k e r s 3 1 3 9 4 4 0 a ) W e s t g a a r d e t a l ., 1 9 84M a c h i n e o p e r a t o r s 4 5 - 4 9 ) 8 6 T o l a e t a l ., 1 9 88C a r p e n t e r s 4 5 - 4 9 ) 7 6 T o l a e t a l ., 1 9 88O f f i c e w o r k e r s 4 5 - 4 9 ) 6 2 T o l a e t a l ., 1 9 88S t r a w b e r r y p i c k e r s 1 4 6 0 1 0 1 ) M a e d a e t a l ., 1 9 80E g g p l a n t p i c k e r s 1 1 4 3 4 0 1 ) M a e d a e t a l . , 1 9 80Note: a ) i n c l u d e s a n k l e s ; f ) i n c l u d e s f e e t ; 1 ) i n c l u d e s le g s ; s ) i n c l u d e s s h o u l d e r ; t ) i n c l u d e s t h i g h . S o m e v a l u e s e s t i m a t e d f r o mg r a p h s .


3/19

W M Keyserling et al / Checklist fo r evaluating ergonomic risk factors 285o f th e a d v e r s e h e a l t h e f f e c t s a s s o c i a t e d w i t h a w k -w a r d l o w e r e x t r e m i t y , t r u n k a n d n e c k p o s t u r e s .

P a i n i s o f t e n a s s o c i a t e d w i t h a w k w a r d p o s t u r e s( s e e ta b l e 1 ). T a b l e 2 s u m m a r i z e s t h e p e r c e n t a g eo f w o r k e r s i n d i f f e r e n t i n d u s t r ie s w h o h a v e e x p e -r i e n c e d p a i n i n t h e l o w e r e x t r e m i t y , t r u n k o rn e c k . T h e s e d a t a a r e t a k e n f r o m s t u d i e s t h a ti n v e s t i g a t e d t h e r e l a t i o n s h i p b e t w e e n w o r k i n gp o s t u r e a n d d i s c o m f o r t , p a i n a n d / o r i nj ur y . T h ed a t a i n t a b l e 2 i n d i c a t e t h a t l o w b a c k p a i n i s ac o m m o n p r o b l e m . F u r t h e r m o r e , p a i n i s e x p e r i-e n c e d i n t h e n e c k , k n e e , c a l f a n d f e e t b y a b o u to n e - t h i r d o f w o r k e r s i n s o m e i n d u s t ri e s .

M a n y m e t h o d s f o r m e a s u r i n g p o s t u r e a r ea v a i l a b l e . A t h a ( 1 9 8 4 ) r e v i e w e d p o s t u r e m e a s u r e -m e n t f o r s p o r t s a p p l i c a t i o n s i n c lu d i n g : p h o t o -g r a p h i c m e t h o d s , g o n i o m e t e r s , a c c e l e r o m e t e r sa n d o p t o - e l e c t r o n i c c o - o r d i n a te a n a ly z e r s. M a n yo f th e s e m e t h o d s a r e i m p r a c t ic a l f o r u se o n t h es h o p f l o o r b e c a u s e o f c o s t, c o m p l e x i t y , c a l i b r a t i o nd i f fi c u l ti e s a n d t h e i n v a si v e n e ss o f t h e t e c h n i q u e .O t h e r m e t h o d s f o r d e s c ri b in g p o s t u r e i n c lu d ed i r e c t o b s e r v a t i o n a n d m a n u a l r e c o r d i n g u s i n gf o r m s ( K a r h u e t a l . , 1 9 7 7 ; C o r l e t t e t a l . , 1 9 7 9 ;P r i e l , 1 9 7 4 ) a n d c o m p u t e r - a i d e d m e t h o d s ( K e y -s e r l i n g , 1 9 8 6 ; K i l b o m e t a l . , 1 9 8 6 b ) . L i m i t a t i o n so f t h e s e m e t h o d s f o r u s e a s s h o p - f l o o r s c r e e n i n gt o o l s i n c l u d e : c o s t , t h e l e v e l o f t r a i n i n g r e q u i r e d ,t h e a p p l i c a t i o n t i m e a n d t h e n e e d f o r a d d i t i o n a la n a l y s i s u s i n g s p e c i a l e q u i p m e n t t o d e t e r m i n e t h ee x p o s u r e l e v e l . I n s p i t e o f t h e s e l i m i t a t io n s , t h e s em e t h o d s a n d o t h e r s h a v e b e e n u s e d t o d e s c r i b ew o r k e r s ' p o s t u r e .

T h e s t u d y r e p o r t e d b e l o w i n v o l v e d t h r e e s t e ps .T h e f i r st s te p w a s t o d e s i g n a n d d e v e l o p a s c r e e n -i n g t o o l t h a t c o u l d b e u s e d q u i c k l y , e a s i l y , a n da c c u r a t e l y b y s h o p f l o o r w o r k e r s w i t h a m i n i m u mo f t ra i n in g o r e q u i p m e n t . T h e s c r e e n i n g to o l d e -v e l o p e d w a s a c h e c k l i s t, a s h a s r e c e n t l y b e e ns u g g e s t e d b y O S H A . D u e t o t h e s i g n i fi c a n t e r -g o n o m i c p r o b l e m s i n th e m e a t p a c k i n g i n d us t ry ,t h e O c c u p a t i o n a l S a f e t y a n d H e a l t h A d m i n i st r a -t io n ( O S H A ) i ss u e d a d o c u m e n t t it le d E r g o -n o m i c P r o g r a m M a n a g e m e n t G u i d e l i n e s f o rM e a t p a c k i n g P l a n t s ( O S H A , 1 99 0 ). T h i s p u b l i-c a t i o n s t a t e s :

The goal of any safety and hea l th program is to preventinjuries and illnesses by rem oving their c auses. For er-gonomics, this go al is to eliminate or materially reduce worker

exposure to ergono michazards that lead to cum ulative traumadisorde rs and related injuries and illnesses.T h e O S H A g u id e li ne s r e c o m m e n d t h a t a n e f f ec -t iv e c o n t r o l p r o g r a m i n c l u d e a s y s t e m a t i c a n a ly s iso f t h e w o r k s i t e t o r e c o g n i z e , i d e n t i f y a n d c o r r e c te r g o n o m i c h a z a rd s . T h e g u i d e li n e s f u r t h e r r e c -o m m e n d t h e u s e o f a c h e c k l is t to i d e n t i f y j o b sw i t h e r g o n o m i c h a z a r d s , in c l u d i n g a w k w a r d p o s -t u r e s . T h e s e c o n d s t e p w a s t o u s e t h e c h e c k l i s t t oa n a l y z e a v a r i e t y o f i n d u s t r i a l t a s k s . T h e f i n a ls t e p w a s t o c o m p a r e t h e c h e c k l i s t r e s u l t s w i t h t h er e s u l t s o f e x p e r i e n c e d e r g o n o m i s t s t o c o n f i r mt h a t s h o p f l o o r w o r k e r s w i t h o n e w e e k o f e r -g o n o m i c t r a i n i n g c o u l d c o r r e c t l y i d e n t if y e r-g o n o m i c s t r e s s e s r e s u l t i n g f r o m a w k w a r d p o s -t u r e s .

T h e f o l l o w i n g s e c t i o n s d e s c r ib e t h e d e v e l o p -m e n t , i m p l e m e n t a t i o n a n d e v a l u a t i o n o f a c h e c k -l i s t t o e v a l u a t e e r g o n o m i c r i s k f a c t o r s a s s o c i a t e dw i t h a w k w a r d p o s t u r e s o f t h e n e c k , tr u n k a n dl o w e r e x t r e m i t i e s . A s i m i l a r c h e c k l i s t d e s i g n e d t os c r e e n f o r u p p e r e x t r e m i t y r i s k f a c t o r s ( K e y s e r -l i n g e t a l . , i n p r e s s ) w a s a l s o d e v e l o p e d a s p a r t o ft h i s s t udy .

e t h o d s

O b j e c t iv e s a n d e n v i r o n m e n tT h e c h e c k l i s t d e s c r i b e d b e l o w w a s d e v e l o p e d

i n c o n j u n c t i o n w i t h a 4 2 - m o n t h l o n g i t u d i n a l s t u d yt o e v a l u a t e t h e e f f e c t i v e n e s s o f a j o i n t u n i o n -m a n a g e m e n t p r o g r a m i n r e d u c i n g e r g o n o m i c in -j u r i e s a n d d i s o r d e r s i n a l a r g e a u t o m o t i v e c o r p o -r a ti o n . T h i s s tu d y w a s p e r f o r m e d a t f o u r w o r ks it e s ( a n e n g i n e p l a n t , a m e t a l s t a m p i n g p l a n t a n dt w o p a r t s d i s t r i b u t i o n w a r e h o u s e s ) , a l l l o c a t e d i nt h e s a m e m e t r o p o l i t a n a r e a .

T h e c h e c k l i s t w a s d e s i g n e d t o b e a s t r u c t u r e de r g o n o m i c j o b e v a l u a t i o n t o o l f o r u s e o n t h ep l a n t f l o o r b y r e p r e s e n t a ti v e s o f m a n a g e m e n t a n dl a b o r . A l l u s e r s p a r t i c i p a t e d i n a o n e - w e e k t r a i n -i n g p r o g r a m t h a t i n c l u d e d l e c t u r e s o n e r g o n o m i cf u n d a m e n t a l s a s w e l l a s p r/ ic t ic a l e x e r c i s e s o n jo ba n a ly s i s a n d u s e o f t h e c h e c k l is t . O t h e r t h a n t h iso n e - w e e k c o u r s e , m o s t u s e r s h a d n o a d d i t i o n a lf o r m a l t r a i n i n g i n e r g o n o m i c s .

T h e p o s t u r e c h e c k l i s t w a s d e s i g n e d t o f u n c t i o n


4/19

286 W.M. Keyserlinget al. / Che cklist or eL aluating ergonom ic risk acto rsas a rap id , sens i t i ve screen ing too l t o i d e n t i f y jo b sw i t h p o t e n t i a l l y h a r m f u l e x p o s u r e s t o e r g o n o m i cs t r e s s . T h e s p e e d - o f . u s e c r i t e r i o n r e q u i r e d t h a t i ts h o u l d b e c o m p l e t e d i n a b o u t f i ve m i n u t e s . T h es e n s i ti v i ty c r i t e r i o n r e q u i r e d t h a t t h e c h e c k l i s ti d e n t i f y t h e p r e s e n c e o f a l l p o t e n t i a l l y h a r m f u lp o s t u r a l s t r e s s e s . A s a s c r e e n i n g t o o l , t h e c h e c k -l i s t w a s d e s i g n e d t o b e b i a s e d , m o r e l i k e l y t oc l as s if y a n a c c e p t a b l e j o b a s a p r o b l e m j o b ( af a l s e p o s i t i v e ) t h a n t o c l a ss i fy a p r o b l e m j o b as

a c c e p t a b l e ( a f a ls e n e g a t iv e ) . T h e c h e c k l i s t w a sn o t d e s i g n e d t o b e a d i a g n o s t i c t o o l . T h e r e f o r e , i td i d n o t p r o v i d e s u f f i c i e n t i n f o r m a t i o n t o i d e n t i f ys p e c i f ic w o r k a t t r i b u t e s r e s p o n s i b l e f o r e x c e s s i v es t r e s s o r p r o v i d e i n s i g h t s a s t o h o w t h e j o b c o u l db e r e d e s i g n e d t o r e d u c e e r g o n o m i c s t r e s s . ( A d -d i t i o n a l a n a l y s e s u s i n g o p e n - e n d e d m e t h o d s w e r er e q u i r e d t o a c c o m p l i s h t h e s e o b j e c t i v e s . T h e s ef o l l o w - u p a n a l y s e s w o u l d a l s o i d e n t i f y s i t u a t i o n sw h e r e t h e c h e c k l i s t p r o d u c e d a f a l s e p o s i t iv e . )C h e c k l is t f u n d a m e n t a l s

A c o m p l e t e v e r s io n o f th e P o s t u r e C h e c k l is ta n d t h e a s s o c i a t e d e x p l a n a t o r y n o t e s a r e p r e -s e n t e d i n t h e A p p e n d i x . T h e c h e c k l i s t c o n s i s t e do f a s e r i e s o f o b j e c t i v e q u e s t i o n s w i t h m u l t i p l ec h o i c e r e s p o n s e s . E a c h q u e s t i o n w a s d e s i g n e d t oe v a l u a t e th e p r e s e n c e a n d d u r a t i o n o f e x p o s u r et o a w k w a r d p o s t u r e s . T h e f o ll o w in g c a t e g o r i e sw e r e u s e d t o e s t im a t e t h e d u r a t i o n o f e x p o s u r e :

N e v e r : T h e j o b i n v o l v e d n o e x p o s u r e t o t h ep a r t i c u l a r p o s t u r e .S o m e t i m e s : T h e p o s t u r e w a s r e q u i r e d t o p e r -f o r m t h e j o b , h o w e v e r t h e t o t a l d u r a t i o n o f t h ep o s t u r e w a s l e ss t h a n o n e - t h i r d o f t h e w o r kc y c l e o r w o r k d a y .G r e a t e r t h a n o n e - t h i r d : T h e p o s t u r e w a s r e -q u i r e d t o p e r f o r m t h e j o b a n d t h e t o t a l d u r a -t i o n w a s g r e a t e r t h a n o n e - t h i r d o f t h e w o r kc y c l e o r w o r k d a y .T h e r e s p o n s e t o e a c h q u e s t i o n r e s u l t e d i n a

s t r e s s r a t i n g ( s e e c h e c k l i s t i n t h e A p p e n d i x ) t h a tu t i l i z e d a t h r e e - l e v e l q u a l i t a t i v e s c a l e :

Ze r o : U s i n g t h e p o s t u r e f o r t h e i n d i c a t e d d u -r a t i o n p r e s e n t e d i n s i g n i f i c a n t r i s k o f i n j u r y o ri l lness .C h e c k : M o d e r a t e e x p o s u r e t o p o s t u r a l s t re s sw a s p r e s e n t , i n d i c a t i n g a p o t e n t i a l r i s k o f i n -j u r y t o s o m e w o r k e r s .

S tar : S u b s t a n t i a l e x p o s u r e t o p o s t u r a l s t r e s sw a s p r e s e n t , i n d i c a t i n g s i g n i f i c a n t r i sk o f i n-j u r yT h e m o s t c o m m o n m a p p i n g b e t w e e n t h e d u r a -

t io n o f a w k w a r d p o s t u r e a n d t h e a s s o c i a t e d s tr e s sr a t i n g w a s :D u r a t i o n . . . . . . S t re s s r a ti n g

N e v e r . . . . . Z e r oS o m e t i m e s . . . . . C h e c k

G r e a t e r t h a n o n e - t h ir d - . . . . . S t a rH o w e v e r , t h e r e w e r e s e v e r a l i m p o r t a n t d e v i a t i o n sf r o m t h i s g e n e r a l r u l e , a s d i s c u s s e d i n t h e n e x ts e c t i o n .

O n c e t h e c h e c k l i s t w a s c o m p l e t e d , t h e t o t a ln u m b e r o f ch e c k s a n d s t a rs w e r e s u m m e d , p r o -d u c i n g a n o v e r a l l s c o r e o f p o s t u r e s t r e s se s . ( N o t e :B e c a u s e t h e r a t i n g s y s t e m w a s q u a l i t a t i v e ( i .e .,

s t a r r e s p o n s e s o n d i f f e r e n t q u e s t i o n s d i d n o tn e c e s s a r i l y i n d i c a t e e q u a l l e v e l s o f a b s o l u t e r i s k ) ,c h e c k l i s t u s e r s w e r e i n s t r u c t e d t o i n t e r p r e t t h eo v e r a l l s c o r e w i t h c a u t i o n . S i n c e t h e c h e c k l i s t w a sd e s i g n e d a s a s c r e e n i n g t o o l t o i d e n t if y j o b s w h i c hs h o u l d u n d e r g o f o l l o w - u p a n a l y s e s , a n y j o b r e -c e iv i ng o n e o r m o r e S t a r s w a s c o n s i d e r e d toh a v e h i g h p r i o r i t y f o r a d d i t i o n a l i n v e s t i g a t i o n a n da n a l y s i s . )D e v e l o p m e n t o f c h e c k l i st q u e s ti o n s

T h e c h e c k l i s t w a s s t r u c t u r e d t o i d e n t i f y t h r e eg e n e r a l c a t e g o r i e s o f e x p o s u r e t o a w k w a r d p o s -t u r e s : L o w e r E x t r e m i t i e s , T r u n k a n d N e c k . R e f e rt o t h e a p p e n d i x f o r d e t a i l s r e g a r d i n g p o s t u r e a n da c t iv i ty d e f i n i ti o n s , d u r a t i o n c a t e g o r i e s a n d a s s o -c i a t e d s t r e s s r a t i n g s .Lo we r e x t r e m i t y p o s t u r e s a n d a c t i v i t i e s

W o r k s i t ua t i on s t h a t r e q u i r e d e m p l o y e e s tos t a n d s t a t i o n a r y w i th t h e f e e t b e a r i n g t h e b o d y ' sw e i g h t f o r a p r o l o n g e d p e r i o d o f t i m e w e r e i d e n -t i f i e d i n Q u e s t i o n 1 . S t a n d i n g s t a t i o n a r y c a n b e ar i s k f a c t o r f o r p a i n i n t h e l o w b a c k , h i p s , l e g s ,k n e e s , a n k l e s a n d f e e t ( B u c k l e e t a l . , 19 8 6; R y a n ,1 9 89 ). S t a n d i n g h a s a l s o b e e n a s s o c i a t e d w i t hc o m p r e s s i o n o f t h e p o s t e r i o r t i bi a l n e r v e a t t h ea n k l e ( A g u a y o , 1 9 7 5 ) , i n c r e a s e d v e n o u s p r e s s u r ei n t h e l e g s a n d v a r i c o s e v e i n s ( C o f f m a n , 1 9 7 5 ) .B e c a u s e t h e s e s y m p t o m s a r e t h e r e s u l t o f p r o -l o n g ed e x p o s ur e , N e v e r a n d S o m e t i m e s w e r e


5/19

W M Keyserling et al / Checklis t fo r evaluating ergonomic r isk factors 87a s s ig n e d r a ti n g s o f Z e r o , w h i le > 1 / 3 c y c l ew a s a s s ig n e d a C h e c k .

W o r k e r u s e o f a f o o t p e d a l w h i le s t a n d i n g w a st h e f o c u s o f Q u e s t i o n 2 . S t a n d i n g u s e o f a f o o tp e d a l h a s b e e n f o u n d t o b e a r i s k f a c t o r f o r p a i na t th e k n e e , h i p a n d / o r l o w b a c k ( C o r l e t t e t al .,1978) .

L y i n g o n t h e b a c k o r s i d e , a d d r e s s e d i n Q u e s -t i o n 3 , w a s i n c l u d e d i n t h e c h e c k l i s t f o r s e v e r a lr e a s o n s . F i r s t, l y in g d o w n a n d g e t t i n g u p c a np l a c e a h ig h m e t a b o l ic d e m a n d o n t h e o p e r a t o r ,e s p e c i a l l y i f t h e t a s k i s r e p e t i t i v e . S e c o n d , l y in gd o w n , w h e n a s s o c i a te d w i th m a i n t e n a n c e p r o c e -d u r e s , o f t e n i n v o lv e s c o n f i n e d s p a c e s , c o n s t r a i n e dp o s tu r e s a n d / o r i n fr e q u e n tl y p e r f o r m e d ( a n dt h e r e f o r e , u n a c c u s t o m e d ) t a sk s. T h e r e s u lt in gs t r e s s e s a r e o f t e n c i t e d a s r i s k f a c t o r s f o r p a i n i nv a r i o u s p a r t s o f t h e b o d y . T h i r d , l y i ng d o w n o f t e nr e s u l t s i n i n a d e q u a t e b o d y s u p p o r t , s t r e s s i n g t h em u s c l e s u s e d t o s u p p o r t t h e h e a d , a r m s o r l e g s ,o r c a u s i n g m e c h a n i c a l c o n t a c t s t r e s s w i t h t h ew o r k s t a t i o n .

T h e d u r a t i o n o f k n e e l i n g w a s e v a l u a t e d b yQ u e s t i o n 4 . K n e e l i n g w a s d e f i n e d a s o n e o r b o t hk n e e s t o u c h i n g t h e g r o u n d . K n e e l i n g h a s b e e n :( 1 ) r a t e d a s tr e s s fu l p o s t u r e b y f o u n d r y w o r k e r sa n d e r g o n o m i c e x p e r t s ( K a r h u e t a l ., 1 9 7 7) ; ( 2 )r e p o r t e d t o i n c r e a s e t h e r is k o f p a i n o r i n ju r y att h e k n e e ( T a n a k a e t a l. , 19 8 2) ; a n d ( 3 ) r e p o r t e dt o c a u se c o m p r e s s i o n o f t h e p e r o n e a l n e r v e( S p a a n s , 1 9 7 0 ) .

S q u a t t i n g ( a n i n c l u d e d a n g l e b e t w e e n t h e t h i g ha n d c a l f o f l es s t h a n 1 5 0 d e g r e e s ) w a s i d e n t i f i e di n Q u e s t i o n 5 . S q u a t t i n g h a s b e e n : ( 1 ) r a t e d a s as t r es s f u l p o s t u r e b y f o u n d r y w o r k e r s a n d e r -g o n o m i c e x p e r t s ( K a r h u e t a l ., 1 9 7 7 ); ( 2 ) r e p o r t e dt o ca u s e c o m p r e s s i o n o f t h e c o m m o n p e r o n e a ln e r v e ( K o l l e r e t a l . , 1 9 8 0 ; S a n d h u e t a l . , 1 9 7 6 ) ;a n d ( 3 ) r e p o r t e d t o c a u se t h e c o m p r e s s i o n o f t h ep o s t e r i o r t i b i a l n e r v e ( J o u b e r t , 1 9 7 2 ) . D e e ps q u a t t i n g h a s b e e n a s s o c i a t e d w i t h c o m p r e s s i o no f th e p l a n t a r n e r v e s ( A g u a y o , 1 9 7 5 ) a n d h a sb e e n s h o w n to i n c re a s e b o n e - o n - b o n e a n d c o m -p r e s s i o n f o r c e s i n t h e k n e e b y a b i o m e c h a n i c a lm o d e l ( A r i e l , 1 9 7 4 ) .T r u n k p o s t u r e

S i tt in g d u r i n g t h e w o r k d a y w a s e v a l u a t e d i nQ u e s t i o n s 6 a n d 7 . S it t in g w i th a b a c k s u p p o r tw a s t h e f o c u s o f Q u e s t i o n 6 . S i tt i n g ha s b e e n

s h o w n t o b e a r i s k f a c t o r i n t h e d e v e l o p m e n t o fl o w b a c k p a i n ( M a g o r a , 1 9 72 ); r e p o r t e d t o c a u s ec o m p r e s s i o n o f t h e s c i a t ic n e r v e ( D e v e r e l l e t a l .,1 9 6 8 ; A g u a y o , 1 9 7 5 ) , a n d f o o t s w e l l i n g ( W i n k e l e ta l. , 1 9 8 8) . S it t i n g w i t h o u t a b a c k s u p p o r t w a sa d d r e s s e d i n Q u e s t i o n 7 . S i t t i n g i n a s e a te q u i p p e d w i t h l u m b a r s u p p o r t h a s b e e n s h o w n t or e d u c e t h e s t r e s s o n t h e l u m b a r s p i n e i n b i o m e -c h a n i c a l s t u d i e s ( A n d e r s s o n e t a l . , 1 9 7 4 a ;A n d e r s s o n e t a l. , 1 97 4 b ) . B e c a u s e s i t ti n g w i t hb a c k s u p p o r t r e d u c e s t h e s t r e s s o n t h e b a c k ,N e v e r a n d S o m e t i m e s s it ti ng w e r e r a t e d a Z e r oo n t h e c h e c k l is t , w h i l e s it ti n g f o r m o r e t h a n 1 / 3o f th e d a y w a s r a t e d a C h e c k .

N o n - n e u t r a l t r u n k p o s t u r e s w e r e e x a m i n e d u s -i n g Q u e s t i o n s 8 t h r o u g h 1 1 . P o s t u r e s s u c h a sf l e x i o n , t w i s t i n g , o r l a t e r a l b e n d i n g h a v e b e e na s s o c i a t e d w i t h i n c r e a s e d r is k o f b a c k p a i n ( P u n -n e t t e t a l . , 1 9 9 1 ) . O t h e r r i s k s i n c l u d e : i n c r e a s e dd i s c o m f o r t i n t h e l o w e r e x t r e m i t i e s a n d d e c r e a s e dt i m e a p o s t u r e c a n b e m a i n t a i n e d a s t h e a n g l e o ff l e x i o n i n c r e a s e s ( B o u s s e n n a e t a l. , 1 9 82 ) ; a n di n c r e a s e d b i o m e c h a n i c a l l o a d s ( A n d e r s s o n e t a l.,1 97 7 ; N a c h e m s o n , 1 9 66 ). B e c a u s e s e v e r e f o r w a r db e n d i n g ( m o r e t h a n 4 5 d e g r e e s f o r w a r d f l e x i o n ) iss o s tr e s s fu l , a n y e x p o s u r e t o t h i s p o s t u r e r e c e i v e da S t a r r a t in g . E x t e n s i o n o f t h e t r u n k ( Q u e s t i o n1 0 ) w a s i n c l u d e d t o c o m p l e t e t h e t r u n k p o s t u r ed e s c r i p t i o n .

e c k p o s t u r eM i l d n e c k f l e x io n o f b e t w e e n 2 0 d e g r e e s a n d

4 5 d e g r e e s w a s t h e f o c u s o f Q u e s t i o n 1 2. N e c kf l e x io n h a s b e e n s h o w n t o b e r e l a t e d t o n e c k p a i na s a f u n c t i o n o f t h e a n g l e o f f l ex i o n , t h e t i m es p e n t w i t h t h e n e c k f l e x e d a n d t h e n u m b e r o ff l e x i o n s p e r h o u r ( H u n t i n g e t a l ., 1 9 8 0; K i l b o m e ta l . , 1986a ; K i l bom e t a l . , 1987 ) . S i nce t hes e s ym p-t o m s d e v e l o p f r o m p r o l o n g e d e x p o s u re , N e v e ra n d S o m e t i m e s w e r e a s si g n ed Z e r o r a ti n gs ;w h i le > 1 / 3 c y c le w a s a s s ig n e d a C h e c kra t i ng .

S e v e r e n e c k f l e x io n o f m o r e t h a n 4 5 d e g r e e sw a s a n a l y z e d u s i n g Q u e s t i o n 1 3 . T h i s p o s t u r e h a sb e e n a s s o c i a t e d w i t h t h e f o l l o w i n g : 3 6 0 p e r c e n ti n c r e a s e i n t h e m o m e n t a b o u t t h e C 7 - T 1 j o i n t,w h i c h m a y b e d a m a g i n g t o t h e p a s s i v e ti s su es u p p o r t i n g t h e l o a d ( H a r m s - R i n g d a h l e t a l . ,1 9 8 6 a ) ; a n d i n c r e a s e d f a t i g u e r a t e s ( C h a f f i n ,1 9 7 3 ) . F i n a l l y , m a x i m a l f o r w a r d n e c k f l e x i o n c a n


6/19

88 W M Keyserling et al / Checklist fo r evaluating ergonomic risk fact orscause pain or discomfort after only 15 minutes ofexposure (Harms-Ringdahl et al., 1986b).

Neck extension (backward bending) of morethan 20 degrees, which is reported to cause neckpain (.VanWely, 1970), was evaluated using Ques-tion 14.

Neck twisting and/or lateral bending of morethan 20 degrees was monitored using Question15. These postures have been shown to result inincreased occurrence of neck and shoulder symp-toms (Tola et al., 1988).U s i n g t h e c h e c k li s t: A s u r v e y o f a w k w a r d p o s t u r e i nf o u r p l a n t s

The checklist was used to evaluate ergonomicstresses resulting from awkward postures on 335jobs in selected departments of four differentplants. These analyses were performed by plantemployees following a one-week ergonomicstraining program that included instruction andpractice in checklist use. Because the checklistswere used prior to the implementation of any jobimprovements to reduce exposures to ergonomicstresses, the resulting data described the status ofposture risk factors at the outset of the jointlabor-management ergonomics program.

Work activities and specific job requirementsvaried considerably among and within the plants.Job requirements in the engine plant (n = 67jobs) included: repetitive manual handling ofmodera tely heavy parts (e.g., 25 kg. engine heads)when loading and unloading automated machin-ing, surface finishing and assembly equipment;visual and tactile inspections of in-process parts;and manual assembly operations. In the metalstamping plant (n = 133 jobs) job requirementsincluded: manual handling of blanks and/or pre-viously stamped parts when loading or unloadingpresses and semi-automated welding equipment;using operating controls such as two-handedsafety buttons to activate power presses andwelding machines; and stacking moderately-heavyfinished components to containers for shipping.At the two warehouses (n = 57 jobs in Ware-house A, n = 78 jobs in Warehouse B), job re-quirements included: manually depalletizing bulkincoming shipments of a variety of light and mod-erately-heavy automotive rep lacement parts (cata-lytic converters, transmission components, brake

components etc.); visual and tactile inspections ofreplacement parts; manual and semi-automatedpackaging of single parts; and manual handling ofpackaged parts for temporary storage or ship-ment.Statistics summarizing responses to checklistquestions are presented in the Results section foreach participating plant and for the total study.Responses that gave the same stress ratings formultiple duration categories were pooled. ThusZe ro stress responses in Questions 1, 6 and 12

were pooled into a duration category of < 1/ 3cycle (see the checklist in the Appendix andtables 5, 6 and 7). Also, the Star stress ratingsin Question 9 were pooled into a duration cate-gory of Any . In addition, a Chi-square test ofindependence (Gibbons, 1971) was used to evalu-ate the significance of plant effects.E v a l u a t i n g t h e c h e c k l i s t a s a s c r e e n i n g t o o l

The checklist presented in the Appendix wasdesigned to function as a rapid screening tool foruse by persons with relatively little training andexperience in ergonomics to identify jobs withpotentially harmful awkward postures. In orderto assess the effectiveness of the checklis t inaccomplishing these objectives, responses tochecklist questions covering trunk and neck pos-tures were compared to the results of exper tcomputer-aided video analyses performed by uni-versity personnel (research engineers and ad-vanced graduate students) with extensive experi-ence in ergonomic job analysis techniques. Thecomparison was made using a subset of 51 of the335 jobs. All 51 of these jobs were analyzed forthe trunk postures. However, of the 51 jobs only24 were analyzed for neck posture. The remain-ing 27 jobs were not analyzed because the work-ers' heads were not captured on video tape forthe whole work cycle. There were two reasons forthe reduced sample size for neck posture compar-isons. First, the worker's face was not included invideo tape, where possible, to maintain theanonymity of subjects. Second, the head wasblocked from view by parts of the workstation orthe worker's body. For a complete description ofthe expert analysis procedures and methodssee Keyserling et al. (1991).The expert analysis of trunk and neck posturewas performed using a quantitative computer-


7/19

W M Keyserling et al / Checklist fo r evaluating ergonom ic risk factors 2 8 9a i d e d p r o c e d u r e K e y s e r l i n g , 1 9 90 ) t h a t m e a -s u r e d t h e a c t u a l t im e a n d t h e p e r c e n t a g e o f t h ew o r k c y c l e d u r i n g w h i ch t h e t r u n k a n d n e c k w e r ei n v a r i o u s p r e - d e f i n e d p o s t u r e s . T h e d e f i n i ti o n so f tr u n k a n d n e c k p o s t u r e s u s e d b y t h e e x p e r t sa n d t h e c h e c k l i s t w e r e t h e s a m e . T h e s e p o s t u r e sa r e d e p i c t e d i n f i g u r e 1 .

T o f a c i l it a t e c o m p a r i s o n w i t h c h e c k l i s t r e s u lt s ,p e r c e n t a g e o f c yc le ti m e s o b t a i n e d i n th e e x p e r ta n a l ys i s w e r e t r a n s f o r m e d i n t o o n e o f t h e f o ll o w -i n g d u r a t i o n c a t e g o r i e s :

None: l e ss t h a n 1 p e r c e n t o f t h e c y c l e t i m e w a ss p e n t i n t h e p o s t u r e o f i n te r e s t ;Some: 1 t o 3 3 p e r c e n t o f t h e c y c l e t i m e w a ss p e n t i n t h e p o s t u r e o f i n te r e s t ;More than one third: m o r e t h a n 3 3 p e r c e n t o ft h e c y c l e t i m e w a s s p e n t i n t h e p o s t u r e o fi n t e r e s t .A s d e s c r i b e d a b o v e , t h e r e s p o n s e s t o s e v e r a l

c h e c k l i s t q u e s t i o n s w e r e p o o l e d b a s e d o n t h es t re s s r a t in g s . T o m a t c h t h e p o o l e d c h e c k l i st c a t e -g o r i e s t h e e x p e r t r e s u l t s f o r Q u e s t i o n s 9 a n d 1 2

T a b l e 3R e s u l t s o f a s u r v e y o f 3 3 5 a u t o m o t i v e j o b s u s i n g a c h e c k l i s t t o i d e n t i f y l o w e r e x t r e m i t y p o s t u r e s a n d a c t iv i t ie s .C r i t e r i o n P l a n t C h e c k l i s t r e s p o n s e S i g.

_< 1 / 3 c y c l e > 1 / 3 c y c l eS t a n d i n g s t a t i o n a r y E n g i n e 8 6 . 6 1 3 .4Q u e s t i o n 1 ) P r e s s e d m e t a l 6 5 . 4 3 4 . 6

W a r e h o u s e A 7 3 .7 2 6 .3W a r e h o u s e B 8 0 .8 1 9 .2O v e r a l l 7 4 . 6 2 5 . 4

N e v e r S o m e - > 1 / 3 c y c let i m e s

L y i n g o n b a c k o r E n g i n e 9 4 . 0 6 . 0 0 . 0s i d e Q u e s t i o n 2 ) P r e s s e d m e t a l 1 0 0 .0 0 . 0 0 . 0

W a r e h o u s e A 9 8 .2 1 .8 0 .0W a r e h o u s e B 1 0 0 .0 0 . 0 0 . 0O v e r a l l 9 8 . 5 1 . 5 0 . 0


U s i n g a f o o t p e d a l E n g i n e 1 0 0 .0 0 . 0 0 . 0w h i l e s t a n d i n g P r e s s e d m e t a l 1 0 0 .0 0 . 0 0 . 0Q u e s t i o n 3 ) W a r e h o u s e A 8 4 .2 5 . 3 1 0 .5

W a r e h o u s e B 8 9 . 7 2 . 6 7 .7O v e r a l l 9 4 . 9 1 . 5 3 . 6


K n e e l i n g E n g i n e 8 0 .6 1 9 .4 0 . 0Q u e s t i o n 4 ) P r e s s e d m e t a l 9 8 .5 1 .5 0 . 0W a r e h o u s e A 8 4 .2 1 5 .8 0 . 0

W a r e h o u s e B 9 3 . 6 5 .1 1 .3O v e r a l l 9 1 . 3 8 . 4 0 . 3

N e v e r S o m e - > 1 / 3 c y cl et i m e s

K n e e s b e n t o r E n g i n e 6 2 .7 3 7 .3 0 .0s q u a t t i n g Q u e s t i o n 5 ) P r e s s e d m e t a l 9 7 . 0 3 . 0 0 . 0

W a r e h o u s e A 3 3 . 3 5 4 . 4 1 2 .3W a r e h o u s e B 7 4 .4 2 4 . 4 1 .3O v e r a l l 7 4 . 0 2 3 . 6 2 . 4

* p < 0 .0 1 u s i n g C h i - s q u a r e t e s t o f i n d e p e n d e n c e .E n g i n e = 6 7 jo b s , P r e s s e d m e t a l = 1 33 j o b s, W a r e h o u s e A = 5 7 jo b s , W a r e h o u s e B = 7 8 jo b s )


8/19

2 9 0 W M Keyserling et al / Checklist fo r evaluating ergonomic risk factorsI c , , f / E / ~ . . - ~ I . ~

FL E X I O N / E X TE N S I O N B E N D I N GS TA N D A R D TR U N K P O S TU R E S

1 Sland Ex tens ion (o r< -20 deg rees) 6 L ie - On Back o r S ide2 Sla nd - Neu lra l 7 Si t - Neu tral3 Stan d - Mild Fiexion (~> 20 degrees) 8 Sit Flexion4 Stan d - Severe Flexion (c~ > 45 degrees) 9 Sit - Bend/Twist5 BenclFfwisl ( ~ or 7 > 20 degrees)

( ~ T W I S T I N G

F L E X I O N B E N D I N GS TA N D A R D N E C K P O S TU R E S

1 Ex len s ldn (o r< 20 deg rees)2 Neu lra l3 Mild Flexion (c~> 20 degrees)4 Sev ere Flexion (0~ > 45 degrees)5 Ben dqw is t ( J~ o r ~> 20 deg rees)

Fig 1 S tandard t runk and neck pos ture used in the expe r ta n a l y s i s K e y s e r l i n g , 1 9 9 0 ).

the categori es were < 33 perc ent and > 33 per-cent.

The checklist results were compared to theexpert analysis using two-way 3 x 3 or 2 x 2 con-tingency tables:Expert Checklist classificationclassification Never Sometim es > 1/ 3 CycleNone = + +Some - = +> 33% Cycle - - =Where the checklist and the expert were inagreement, the table entry would be on the maindiagonal (an = in the above example). Whe rethe checklist over-estimated ergonomic stress rel-ative to the expert analysis, the table entry was inthe uppe r right corner (a + in the aboveexample). Similarly, if the checklist underesti-mated ergonomic stress, the table entry was inthe lower left corner (a - in the example).

e s u l t s

S u r v e y o f p o s t u r a l s t re s s e s b a s e d o n c h e c k l i s t r es p o n s e s

were combined into similar categories. For Ques-tion 9, the categories were No ne and Any(> 1 perc ent of the cycle time). For Ques tion 12,

Lo we r e x t r e m i t y p o s t u r e s a n d a c t i v i ti e sLower extremity postures and activities stresses

evaluated in checklist Questions 1-5 are summar-

T a b l e 4R e s u l t s o f a s u r v e y o f 3 3 5 a u t o m o t i v e j o b s u s i n g a c h e c k l i s t t o i d e n t i fy p o s t u r a l r i sk f a c t o r s a s s o c i a t e d w i t h s i t t in g .C r i t e r i o n P l a n t C h e c k l i s t r e s p o n s e S i g.

_< 1 / 3 c y c l e > 1 / 3 c y c l eS i t t in g w i t h b a c k E n g i n e 9 7 .0 3 . 0s u p p o r t Q u e s t i o n 6 ) P r e s s e d m e t a l 9 8 .5 1 .5W a r e h o u s e A 7 5 .4 2 4 .6

W a r e h o u s e B 8 7 .2 1 2 .8O v e r a l l 9 1 . 6 8 . 4

N e v e r S o m e -t i m e s

S i t ti n g w i t h o u t b a c k E n g i n e 9 2 .5 6 . 0s u p p o r t Q u e s t i o n 7 ) P r e s s e d m e t a l 9 9 .2 0 . 8

W a r e h o u s e A 6 3 .2 3 1 .6W a r e h o u s e B 8 7 .2 1 0.3O v e r a l l 8 9 . 0 9 . 3

> 1 / 3 c y c l e1.50 . 05 . 32 . 61.8

* p < 0 .0 1 u s i n g C h i - s q u a r e t e s t o f i n d e p e n d e n c e .E n g i n e = 6 7 j o b s , P r e s s e d m e t a l = 1 33 j o b s , W a r e h o u s e A = 5 7 j o b s , W a r e h o u s e B = 7 8 j o b s )


9/19

W M Keyserling et aL / Checklis t for ecaluating ergonomic r isk factors 291ized in table 3. Stat ionary stand ing Q1) for morethan one-third of the cycle t ime was required onabout 25 percent of the jobs. I t was most preva-lent in the pressed metal plant where workersopera ted presses and semi-aut omate d welders. Inthe oth er plants , s tat ionary posture was less com-mon since workers had to carry parts betweenconveyors and pallets or bins.

Lying on the back or side Q2) was quite rare,observed on only 1.5 percent of the jobs andusually associated with the setup or servicing ofequipment .

Using a foot pedal while standing Q3) wasrequire d on 5 percent of the jobs. This r isk factorwas observed in the warehouses where foot ped-

als were used for operat ing packaging machinesand various types of industr ial t rucks.

Kneeling Q4) was present in 9 percent of thejobs. In the engine plant, it was associated withmaint enanc e workers se t ting up machines andwith stock handlers working at or near f loor leveldur ing pa l le t iz ing/dep al le t iz ing . In warehouse A,kneeling occurred wh en assembling and f i l l inglarge wooden crates with parts for shipping.

Squatt ing Q5) was recorded in 26 percent ofthe jobs. In the engine plant, it was associatedwith han dli ng parts on the lower levels of pallets.In both warehouses, squatt ing resulted fromworking at the lower levels of pallets and binsand whe n retr ieving parts from a rack storage

Table 5Results of a survey of 335 automotive jobs using a checklist to identify postural risk factors associated with trunk posture.Criterion Plant Checklist response Sig.

Never Some- > 1/3 cycletimesMild forward trunk Engine 7.5 67.2 25.4bending > 20) Pressed metal 12.0 82.7 5.3Question 8) Warehouse A 12.3 54.4 33.3Warehouse B 10.3 64.1 25.6Overall 10.7 70.4 18.8 * *Never AnySevere forward Engine 20.9 79.1trunk bending > 45) Pressed metal 72.2 27.8Question 9) Warehouse A 40.4 59.6Warehouse B 37.2 62.8Overall 48.4 51.6 * *Never Some- > 1/3 cycletimesBackward trunk Engine 94.0 6.0 0.0bending > 20) Pressed metal 97.0 3.0 0.0

Question 10) Warehouse A 84.2 14.0 1.8Warehouse B 97.4 2.6 0.0Overall 94.3 5.4 0.3 *Never Some- > 1/3 cycletimesTwisting or lateral Engine 17.9 68.7 13.4trunk bending > 20) Pressed metal 22.6 74.4 3.0Question 11) Warehouse A 10.5 73.7 15.8Warehouse B 20.5 59.0 20.5Overall 19.1 69.6 11.3 * *

* p < 0.05 using Chi-square test of independence.** p < 0.01 using Chi-square test of independence.Engine = 67 jobs, Pressed metal = 133 jobs, Warehouse A = 57 jobs, Warehouse B = 78 jobs)


10/19

2 9 2 W M Keyserling et al / Check list fo r ecaluating ergonom ic risk factorss y s t e m . L e s s k n e e l i n g a n d s q u a t t i n g w e r e r e -q u i r e d i n t h e p r e s s e d m e t a l p l a n t b e c a u s e p a r t sw e r e s u p p l i e d t o t h e w o r k e r s o n c o n v e y o r s o r i np a r t s b i n s t h a t w e r e p o s i t i o n e d b e t w e e n k n u c k l ea n d e l b o w h e i g h t .

s t o r a g e i n t o i n d i v i d u a l c o n t a i n e r s . I n c o n t r a s t ,s i tt i n g a t t h e o t h e r f a c i l i t ie s w a s e x t r e m e l y r a r e( w i t h f e w e x c e p t i o n s , e . g . i n s p e c t i o n t a s k s ) b e -c a u s e o f th e d i m e n s i o n s o f th e w o r k s t a t i o n a n dm a t e r i a l h a n d l i n g r e q u i r e m e n t s .

Trunk postures s i t tingS u r v e y r e s u l t s f o r s it t in g ( Q 6 a n d 7 ) a r e p r e -

s e n t e d i n ta b l e 4 . E i g h t p e r c e n t o f w o r k e r s s a tw i th b a c k s u p p o r t f o r m o r e t h a n o n e t h i r d o f t h ed a y , w h i l e 1 1 p e r c e n t s a t w i t h o u t b a c k s u p p o r t .T h e s e l o w f i g u r e s a r e a t t r i b u t a b l e t o t h e n a t u r eo f t h e w o r k ( m a t e r ia l s h a n d l i n g a n d m a c h i n eo p e r a t i o n ) a n d t h e w o r k s t a t i o n l a y o u t ( i . e . , i t i su n c o m m o n t o f in d s e a t e d j o b s i n h e a v y m a n u -f a c t u r i n g o r w a r e h o u s e o p e r a t i o n s ) . S i t t i n g w a sm o s t c o m m o n i n w a r e h o u s e s A a n d B , w h e r ew o r k e r s s a t w h i le r e p a c k i n g s m a l l p a r t s f r o m b u l k

Trunk postures s tandingT r u n k p o s t u r e r e s u l t s a r e p r e s e n t e d i n t a b l e 5 .

M i l d f l e x io n ( Q 8 ) o c c u r r e d o n 8 9 p e r c e n t o f t h ej o b s, w i t h 1 9 p e r c e n t o f t h e j o b s r e q u i r i n g t h isp o s t u r e f o r m o r e t h a n o n e - t h i r d o f t h e c y c l e t im e .I n t h e p r e s s e d m e t a l p l a n t , h o w e v e r , o n l y 5 p e r -c e n t o f th e j o bs h a d m o r e t h a n o n e - t h i r d o f c y c les p e n t i n m i l d f l e x i o n . T h i s w a s d u e t o t h e e x t e n -s iv e u s e o f c o n v e y o r s a n d p a r t s b i n s p o s i t i o n e db e t w e e n k n u c k l e a n d e l b o w h e i g h t .

S e v e r e t r u n k f l e x io n ( g r e a t e r t h a n 4 5 d e g r e e s )f o r a n y d u r a t i o n w a s r e q u i r e d o n 5 2 p e r c e n t o f

T a b l e 6R e s u l t s o f a s u r v e y o f 3 3 5 a u t o m o t i v e j o b s u s i n g a c h e c k l i s t t o i d e n t i fy p o s t u r a l r i sk f a c t o r s a s s o c i a t e d w i t h n e c k p o s t u r e .C r i t e r i o n P l a n t C h e c k l i s t r e s p o n s e S i g.

_< 1 / 3 c y c l e > 1 / 3 c y c l eM i l d f o r w a r d n e c k E n g i n e 7 0.1 2 9 . 9f l e x i o n > 2 0 ) P r e s s e d m e t a l 8 2 .0 1 8 .0Q u e s t i o n 1 2 ) W a r e h o u s e A 4 5 .6 5 4 . 4

W a r e h o u s e B 6 7 .9 3 2 .1O v e r a l l 7 0 .1 2 9 . 9


S e v e r e f o r w a r d n e c k E n g i n e 2 9 .9 6 4 . 2 6 . 0f l e x i o n > 4 5 ) P r e s s e d m e t a l 7 1 . 4 2 0 . 3 8 . 3Q u e s t i o n 1 3 ) W a r e h o u s e A 5 2 .6 4 0 . 4 7 .0

W a r e h o u s e B 6 5 .4 2 5 . 6 9 .0O v e r a l l 5 8 . 5 3 3 . 7 7 . 8


B a c k w a r d n e c k E n g i n e 9 2 .5 7 .5 0 . 0b e n d i n g > 2 0 ) P r e s s e d m e t a l 9 8 . 5 1 .5 0 . 0Q u e s t i o n 1 4 ) W a r e h o u s e A 4 5 ,6 4 9.1 5 .3

W a r e h o u s e B 8 4 ,6 1 1 .5 3 .8Ov era l l 85 , 7 13 .1 1 . 8


T w i s t i n g o r l a t e r a l E n g i n e 1 7 . 9 6 5 . 7 1 6 .4n e c k b e n d i n g > 2 0 ) P r e s s e d m e t a l 3 0 ,8 6 3 . 2 6 .0Q u e s t i o n 1 5 ) W a r e h o u s e A 5 . 3 7 0 . 2 2 4 .6

W a r e h o u s e B 3 8 .5 5 1 .3 1 0 .3O v e r a l l 2 5 . 7 6 2 .1 1 2 . 2

p < 0 . 0 1 u s i n g C h i - sq u a r e t e s t o f i n d e p e n d e n c e .E n g i n e = 6 7 jo b s , P r e s s e d m e t a l = 1 3 3 j o b s , W a r e h o u s e A = 5 7 j o b s , W a r e h o u s e B = 7 8 j o b s )


11/19

W M Ke yserling et al / Check list fo r evaluating ergonom ic risk factors 293the jobs. In the engine plant, this posture wasused in 79 percent of the jobs, while in thepressed metal plant exposure occurred in onlyabout 28 percent of the jobs. The engine plantexposure was the result of reaching across 5-foot-wide pallets and/or reaching below kneelevel to get par ts from the lower level s) of palletsplaced on the floor.

The least prevalent trunk risk factor was ex-tension, which was present in only 6 percent ofthe jobs Q10). This posture was most common atwarehouse A about 16 percent of jobs) and wasassociated with industrial truck drivers looking upwhile getting or placing loads.

Twisting or lateral bending of the trunk wasobserved in 81 percent of the jobs Qll ). Fewerworkers in the pressed metal plant used pro-longed twisted/bent postures because of the ef-fective layout of conveyors and part s bins.

eck postureNeck posture survey results are presented in

table 6. Mild neck flexion of 20 degrees to 45degrees Q12) for more than one-third of thecycle time was found in 30 percent of the jobs,with a maximum of 54 percent on the jobs inwarehouse A. In this plant, neck flexion occurredon jobs where bulk parts were packaged intoindividual containers on low benches and ma-chines.

Severe neck flexion of more than 45 degreesQ12) was observed in 41 percent of the jobs. The

range was from 29 percent of the jobs in pressedmetal to 70 percent of the jobs in the engineplant. Neck flexion was required in the engineplant when working at the lower levels of palletsand in assembly and inspection tasks located at orbelow waist height.

Neck extension was relatively uncommon, pre-sent in only 14 percent of the jobs. In warehouseA, however, it was observed in 54 percent of thejobs, due to the number of jobs which requiredlooking up i.e. industrial truck driver).

Twisting or lateral bending of the neck wasrequired in 74 percent of the jobs. Warehouse Astands out again with 95 percent of the jobsrequiring some twisting or lateral bending and 24percent of the jobs requiring prolonged twisting/bending. The twisting or lateral bending was re-quired in the two main tasks at warehouse A: t)

T a b l e 7C h e c k l i s t v s . e x p e r t a n a l y s is o f p o s t u r a l s t r e s s e s a s s o c i a t e dw i t h m i l d t r u n k f l e x i o n ( 2 0 - 4 5 ) .E x p e r t s C h e c k l i s t r e s u l tr e s u l t s N e v e r S o m e t i m e s > 1 / 3 c y cl eN o n e

( < 1 cyc le ) 0 7 3S o m e

( 1 - 3 3 c y c l e ) 2 2 4 1 5> 33 cyc le 0 0 0P e r f e c t a g r e e m e n t ( m a i n d i a g o n a l ) = 2 4 j o b s, 4 7 p e r c e n t o fj o b s i n s a m p l eC h e c k l i s t r a t i n g > E x p e r t r a t i n g = 2 5 j o b s, 4 9 p e r c e n t o f j o b si n s a m p l eC h e c k l i s t r a t i n g < E x p e r t r a t i n g = 2 j o b s , 4 p e r c e n t o f j o b s i ns a m p l e

T a b l e 8C h e c k l i s t v s . e x p e r t a n a l y s is o f p o s t u r a l s t r e s s e s a s s o c i a t e dw i t h s e v e r e t r u n k f l e x io n ( m o r e t h a n 4 5 ).E x p e r t C h e c k l i s t r e s u l tr e s u l t N e v e r S o m e t i m e sN o n e

( < 1 cyc le ) 17 16S o m e

( > 1 cyc le ) 1 17P e r f e c t a g r e e m e n t ( m a i n d i a g o n a l ) = 3 4 j o b s, 6 7 p e r c e n t o fj o b s i n s a m p l eC h e c k l i s t r a t i n g > E x p e r t r a t i n g = 1 6 j o b s , 3 1 p e r c e n t o f j o b si n s a m p l eC h e c k l i s t r a t i n g < E x p e r t r a t i n g = 1 jo b s , 2 p e r c e n t o f j o b s i ns a m p l e

T a b l e 9C h e c k l i s t v s . e x p e r t a n a l y s is o f p o s t u r a l s t r e s s e s a s s o c i a t e dw i t h t w i s t i n g o r l a t e r a l b e n d i n g o f t h e t r u n k ( > 2 0 ) .E x p e r t s C h e c k l i s t r e s u l tr e s u l t s N e v e r S o m e t i m e s > 1 / 3 c y cl eN o n e

( < 1 cyc le) 3 16 5S o m e

( 1 - 3 3 c y c l e ) 5 1 5 6> 33 cyc le 0 1 0P e r f e c t a g r e e m e n t ( m a i n d i a g o n a l ) = 1 8 j o b s, 3 5 p e r c e n t o fj o b s i n s a m p l eC h e c k l i s t r a t i n g > E x p e r t r a t i n g = 2 7 j o b s , 5 3 p e r c e n t o f j o b si n s a m p l eC h e c k l i s t r a t i n g < E x p e r t r a t i n g = 6 j o b s , 1 2 p e r c e n t o f j o b s i ns a m p l e


12/19

2 9 4 W M Keyserling et al / Checklist fo r ecaluating ergonomic risk fact orsT a b l e 1 0C h e c k l i s t v s . e x p e r t a n a l y s i s o f p o s t u r a l s t r e s s e s a s s o c i a t e dw i t h m i l d n e c k f l e x i o n (2 0 - 4 5 ) .

T a b l e 1 2C h e c k l i s t v s . e x p e r t a n a l y s i s o f p o s t u r a l s t r e s s e s a s s o c i a t e dw i t h n e c k e x t e n s i o n ( > 2 0 ) .

E x p e r t C h e c k l i s t r e s u l t E x p e r t s C h e c k l i s t r e s u l tr e s u l t < 1 / 3 c y c l e > 1 / 3 c y c le r e s u l t sS o m e N o n e

( 1 - 3 3 c y c l e ) 8 7 ( < 1 c y c l e ) 1 8 2 1> 3 3 c y c l e 9 0 S o m e

( 1 - 3 3 c y c l e ) 3 0 0> 33 cyc le 0 0 0e r f e c t a g r e e m e n t ( m a i n d i a g o n a l ) = 8 j o b s, 3 3 p e r c e n t o f jo b si n s a m p l e

C h e c k l i s t r a t i n g > E x p e r t r a t i n g = 7 jo b s , 2 9 p e r c e n t o f j o b s i ns a m p l eC h e c k l i s t r a t i n g < E x p e r t r a t i n g = 9 j o b s, 3 8 p e r c e n t o f j o b s i ns a m p l e

N e v e r S o m e t i m e s > 1 / 3 c y cl e

P e r f e c t a g r e e m e n t ( m a i n d i a g o n a l ) = 1 8 j o b s, 7 5 p e r c e n t o fj o b s i n s a m p l eC h e c k l i s t r a t i n g > E x p e r t r a t i n g = 3 jo b s , 1 2 p e r c e n t o f jo b s i ns a m p l eC h e c k l i s t r a t i n g < E x p e r t r a t i n g = 3 jo b s , 1 2 p e r c e n t o f jo b s i ns a m p l e

op e r a t in g in d u s t r ia l t r u c k s an d 2 ) r e p ac k in g b u lkp ar t s in t o in d iv id u a l c on t a in e r s .Che ckl i s t responses us. exp er t f in d in gs

T h e r e s u l t s o f t h e t w o - w a y c o m p a r i s o n s b e -t w e e n t h e c h e c k l i s t a n d e x p e r t r e s u l t s a r e p r e -s e n t e d i n t a b l e s 7 t h r o u g h 1 3 . T a b l e 1 4 s u m m a r -i z e s t h e s e c o m p a r i s o n s l i s t i n g t h e c h e c k l i s t i t e mb e i n g c o m p a r e d , t h e n u m b e r o f j o bs u s e d in t h ec o m p a r i s o n a n d t h e n u m b e r a n d p e r c e n t o f j o bsw h e r e :1 ) t h e tw o m e t h o d s w e r e in a g r e e m e n t ,2 ) t h e c h e c k l i s t o v e r e s t i m a t e d t h e r is k f a c t o r

e x p o s u r e c o m p a r e d t o t h e e x p e r t a n a l y s i s ,

3 ) t h e c h e c k l i s t u n d e r e s t i m a t e d t h e r i s k f a c t o re x p o s u r e c o m p a r e d t o t h e e x p e r t a n a l y s i s .

4 ) t h e c h e c k l is t o v e r e s t i m a t e d o r a g r e e d w i t ht h e e x p e r t r e s u l t s o u r m e a s u r e o f s e n s it iv i ty ) .

A s c a n b e s e e n f r o m t h e r i g h t m o s t c o l u m n i nT a b l e 1 4 , t h e c h e c k l i s t f u n c t i o n e d a s a s e n s i t i v es c r e e n i n g t o o l f o r a l l o f t h e p o s t u r e s e x c e p t m i ldn e c k f l e x i o n t a b l e 1 0 ) a n d t w i s t e d o r la t e r a l l yb e n t n e c k t a b l e 13 ). A n o t h e r p r o b l e m e v i d e n tf r o m t a b l e 1 4 is t h a t f o r m i l d t r u n k f l e x i o n t a b l e7 ) a n d t r u n k t w i s t e d o r l a t e r a l ly b e n t t a b l e 9 ) t h ec h e c k l i s t o v e r e s t i m a t e d t h e e x p o s u r e t o t h e s e

T a b l e 1 1C h e c k l i s t v s . e x p e r t a n a l y s i s o f p o s t u r a l s t r e s s e s a s s o c i a t e dw i t h s e v e r e n e c k f l e x i o n ( > 4 5 ) .E x p e r t s C h e c k l i s t r e s u l tr e s u l t s N e v e r S o m e t i m e s > 1 / 3 c y c leN o n e

( < 1 cyc le ) 14 6 2S o m e

( 1 - 3 3 c y c l e) 1 1 0> 33 cyc le 0 0 0P e r f e c t a g r e e m e n t ( m a i n d i a g o n a l ) = 15 j o b s, 6 3 p e r c e n t o fj o b s i n s a m p l eC h e c k l i s t r a t i n g > E x p e r t r a t i n g = 8 jo b s , 3 3 p e r c e n t o f j o b s i ns a m p l eC h e c k l i s t r a t i n g < E x p e r t r a t i n g = 1 j o b s , 4 p e r c e n t o f j o b s i ns a m p l e

T a b l e 1 3C h e c k l i s t v s . e x p e r t a n a l y s i s o f p o s t u r a l s t r e s s e s a s s o c i a t e dw i t h t w i s t i n g o r l a t e r a l b e n d i n g o f t h e n e c k ( > 2 0 ).E x p e r t s C h e c k l i s t r e s u l tr e s u l t s N e v e r S o m e t i m e s > 1 / 3 c y cl eN o n e

( < 1 cyc le ) 1 2 0S o m e

( 1 - 3 3 c y c l e ) 6 7 3> 33 cyc le 1 1 3P e r f e c t a g r e e m e n t ( m a i n d i a g o n a l ) = 1 1 j o b s, 4 6 p e r c e n t o fj o b s i n s a m p l eC h e c k l i s t r a t i n g > E x p e r t r a t i n g = 5 jo b s , 2 1 p e r c e n t o f j o b s i ns a m p l eC h e c k l i s t r a t i n g < E x p e r t r a t i n g = 8 jo b s , 3 3 p e r c e n t o f jo b s i ns a m p l e


13/19


14/19

296 W.M. Keyserling et al. / Checklist or evaluating ergonom ic risk factorsi n t e r v a l b e t w e e n d a t a c o l l e c t io n f o r t h e c h e c k l i sta n d d a t a c o l l e c t io n f o r th e e x p e r t a n a l y s e s w a ss e v e r a l m o n t h s . D u r i n g t h i s p e r i o d s o m e w o r k e r sw e r e r e a s s i g n e d ; a n d t h e r e w e r e m a n y i n s t a n c e sw h e r e d i f f e re n t w o r k e r s w e r e o b s e r v e d f o r t h ec h e c k l i s t a n d e x p e r t a n a l y s e s . T h e r e s u l t i n g d i f -f e r e n c e s i n w o r k e r a n t h r o p o m e t r y a n d i n d iv i du a lw o r k m e t h o d s c o u l d h a v e c o n t r i b u t e d t o p o o rc o r r e l a t i o n o n w o r k - m e t h o d - s e n s i t i v e m e a s u r e ss u c h a s t r u n k a n d n e c k p o s t u r e s . ( T h e s i g n i f i -c a n c e o f a n i n d i v i d u a l ' s w o r k m e t h o d s o n t h en a t u r e a n d m a g n i t u d e o f m e a s u r e d e r g o n o m i cs t r e s s e s h a s b e e n d o c u m e n t e d i n p r e v i o u s s t u d i e s( A a r a s e t a l . , 1 9 8 8 ; H a m m a r s k j o l d e t a l . , 1 9 8 9 ;S t e t s o n e t a l . , 1 9 9 1 ) ) . F u r t h e r m o r e , i n a s m a l ln u m b e r o f w a r e h o u s e j ob s , t h e r e w e r e m i n o rd i f f e r e n c e s in t h e si z e, s h a p e , w e i g h t a n d / o rp a c k a g i n g o f p a r t s c o n s i d e r e d f o r t h e c h e c k l i s ta n d e x p e r t a n a l ys e s . T h e s e d i f f e r e n c e s m a y h a v ec h a n g e d t h e w o r k m e t h o d , c o n t r i b u t i n g t o p o o rc o r r e l a t i o n s i n t h e t r u n k a n d n e c k p o s t u r e c o m -p a r i s o n s . W h i l e t h e l a c k o f c o n s i s t e n c y i n w o r km e t h o d s a n d / o r h a n d l e d p a r t s w o u l d n o t s y st em -a t i c a ll y b i a s t h e r e s u l t s o f e i t h e r t h e c h e c k l i s t o re x p e r t a n a l y se s , i t c o u l d i n c r e a s e t h e n o i s e o rl a ck o f a g r e e m e n t b e t w e e n t h e t w o s y s te m s i n aj o b - b y -j o b c o m p a r i s o n o f f i n d in g s .

D i f f e r e n c e s i n t h e r e s u l ts o f m u l t i p l e e r -g o n o m i c a n a ly s e s w h i c h a r e c a u s e d b y c h a n g e s i nw o r k e r s a n d / o r w o r k m e t h o d s a r e d if f ic u lt t oe x p l a i n . I n o r d e r t o f a c i l i t a t e c o m p a r i s o n s a m o n gd i f f e r e n t j o b a n a l y s i s t e c h n i q u e s i n s i t u a t io n sw h e r e w o r k e r s a n d / o r w o r k m e t h o d s c h a n g e , it ise s s e n t i a l t h a t w o r k e r c h a r a c t e r i s t i c s ( e . g . , b o d ys i z e , d o m i n a n t h a n d e t c . ) a n d w o r k m e t h o d s b em e t i c u l o u s l y d o c u m e n t e d a t t h e t i m e o f d a t a c o l-l e c t i o n . T h i s d o c u m e n t a t i o n c a n p r o v e t o b e i n -v a l u a b l e i n u n d e r s t a n d i n g c h a n g e s i n t h e a p p a r -e n t l e ve l o f e r g o n o m i c s tr e s s w h e n t h e s a m e j o b isa n a l y z e d a t d i f f e r e n t p o i n t s i n t i m e o r b y d i f f e r -e n t m e t h o d s . S e e K e y s e r l i n g e t a l. ( 1 9 9 1 ) f o ra d d i t i o n a l i n f o r m a t i o n o n e r g o n o m i c j o b a n a ly s isa n d d o c u m e n t a t i o n o f w o r k m e t h o d s .

A n o t h e r e x p l a n a t i o n f o r t h e l a c k o f co n s is -t e n c y b e t w e e n t h e c h e c k l is t a n d e x p e r t e v a lu a -t i o n s o f n e c k a n d t r u n k p o s t u r e s i s t h a t t h ec h e c k l is t w a s c o m p l e t e d d u r i n g d i r e c t o b s e r v a t i o no f t h e j o b w h i l e t h e e x p e r t a n a l y s e s w e r e c o m -p l e t e d f r o m v i d e o ta . pe . T h e r e i s a t r a d e o f f b e -t w e e n t h e t w o m e t h o d s . D o i n g t h e a n a l y s is b y

d i r e c t o b s e r v a t i o n a l l o w s t h e a n a l y s t t o m o v ea r o u n d f o r t h e b e s t v i e w , t o u s e t h r e e - d i m e n -s i o n a l c u e s a n d t o t a l k t o t h e w o r k e r a b o u t t h ep o s t u r e s u s ed . T h e a d v a n t a g e o f th e v i d e o t a p ea n a l y s i s i s t h a t t h e t a p e c a n b e p l a y e d i n s l o w a n ds t o p m o t i o n , a l l o w i n g t i m e t o s t u d y a n d m e a s u r et h e p o s t u r e s . A l s o , t h e v i d e o t a p e a l l o w s u s e o ft h e c o m p u t e r t o q u a n t i f y t h e t i m e s p e n t i n e a c hp o s t u r e , w h i l e t h i s w a s e s t i m a t e d b y c h e c k l i s tu s e r s .

L a c k o f a g r e e m e n t m a y h a v e a l s o r e s u lt e df r o m d i f f e r e n c e s in t h e e x p e r t a n d c h e c k l is tm e t h o d s . D u e t o l i m i t a ti o n s im p o s e d b y s o f t w a r ea n d h a r d w a r e , t h e e x p e r t c o u ld c h o o s e o n e a n do n l y o n e o f t h e f o l l o w i n g p o s t u r e s a t a g i v e n t im e :e x t e n s i o n , n e u t r a l , m i l d f le x i o n , s e v e r e f l e x i o n o rt w i s t e d / l a t e r a l l y b e n t. T h e r e f o r e , w h e n a w o r k e ru s e d t w o p o s t u r e s s i m u l t a n e o u s l y , m i l d f l e x i o na n d t w i s t i n g / l a t e r a l b e n d i n g f o r e x a m p l e , o n l yt h e m o r e s t r e s sf u l o n e o f t h e t w o w a s r e c o r d e d i nt h e e x p e r t a n a l y s i s . T h u s , t h e e x p e r t a n a l y s i s u n -d e r - r e p o r t e d a w k w a r d p o s t u r e s t h a t w e r e s i m u l -t a n e o u s . I n c o n t r a s t , t h e c h e c k l i s t r e c o r d e d t h ed u r a t i o n o f e a c h p o s t u r e s e p a r a t e l y . B e c a u s e o ft h is c a p a b i li ty , t h e c h e c k l is t p r o d u c e d h i g h e r p e r -c e n t a g e s t h a n t h e e x p e r t a n a l y s i s f o r a n y s i n g l ec a t e g o r y o f a w k w a r d p o s t u r e s . R e s o u r c e l i m i ta -t i o n s a n d p r o t o c o l d i d n o t p e r m i t a d e t a i l e d a n a l -y s i s o f t h i s e f f ec t .L o n g c y c l e a n d n o n r e p e t it i v e j o b s

V a r i a b i l i t y b e t w e e n t h e c h e c k l i s t a n d e x p e r tr e s u l t s w a s a l s o n o t e d f o r j o b s w i t h l o n g c y c l et i m e s a n d f o r j o b s t h a t w e r e n o t r e p e t i t i v e . A ne x a m p l e o f a l o n g c y c l e t i m e j o b w a s t r a n s f e r r i n gp a r t s b e t w e e n a p a l l e t a n d a p r o d u c t i o n l i n e . T h ec h a n g i n g w o r k h e i g h t o n t h e p a l l e t r e q u i r e d t h a tt h e a n a l y s t s c o n s i d e r t h e p o s t u r e s u s e d f o r t h ee n t i r e p a l l e t a n d n o t j u s t a t t h e m o m e n t o f o b s e r -v a t i o n s . S i n c e l i m i t e d t i m e w a s a v a i l a b l e t o c o m -p l e t e t h e a n a l y s i s , a c t u a l o b s e r v a t i o n s m a y n o th a v e c o v e r e d t h e f u l l r a n g e o f p o s t u r e s u s e d .D i f f e r e n c e s i n th e p o r t i o n o f t h e p a l l e t o b s e r v e dc o u l d l e a d t o p o o r a g r e e m e n t i n t h e c o m p a r i s o no f r e s u l t s .

N o n - r e p e t i t i v e j o b s i n c l u d e d r e p a i r o p e r a t i o n si n t h e e n g i n e a n d p r e s s e d m e t a l p l a n t s . N o n - r e p -e t it iv e j o b s i n t h e w a r e h o u s e s i n c l u d e d p i c k in ga n d p a c k i n g a c t i v it ie s w h e r e a w i d e v a r i e t y o fp a r t s w e r e h a n d l e d . T h e s e j o b s w e r e e s p e c i a ll y


15/19

W.M . Keyserling et al. / Checklist o r ev aluating ergonomic risk actors 297f r u s t r a t i n g t o th e a n a l y st s b e c a u s e t h e a c t i o n s a n dp o s t u r e s w e r e o f t e n d i f f e r e n t f o r e a c h p a r t h a n -d l e d . T h e l a c k o f r e p e t i t i o n i n t h e s e j o b s m a d ed e t e r m i n a t i o n o f th e p o s t u r e s a n d t h e i r d u r a t i o nd i ff ic u lt b e c a u s e m a n y p o s t u r e s w e r e s e e n o n l yo n c e , r e d u c i n g t h e a c c u r a c y o f b o t h t h e e x p e r ta n d c h e c k l i s t r e s u l t s a n d l e a d i n g t o i n c r e a s e dv a r i a b i l i t y i n t h e i r c o m p a r i s o n . T o b e t t e r a n a l y z en o n - r e p e t i t i v e j o b s a d i f f e r e n t a p p r o a c h s u c h a sw o r k s a m p l i n g m i g h t b e h e l p f u l ( N i e b e l , 1 9 8 8 ) .W e a r e c u r r e n t l y e x p lo r in g a l t e r n a ti v e m e t h o d sf o r t h e a n a l ys i s o f n o n - r e p e t i t i v e jo b s .In t e r ana l ys t d i f f e r ences

A n o t h e r s o u r c e o f v a r i a b il i ty w a s t h e d i f fe r -e n c e a m o n g a n a l ys t s. A c o n t r o l l e d s t u d y t o e v a lu -a t e t h e e f f e c t s o f d i f f e r e n t a n a l y st s s t u d y i n g t h es a m e j o b w a s n o t p o s s i b l e d u e t o l i m i t e d r e -s o u r c e s . T h e i n t e r - a n a l y s t v a ri a b i li t y m i g h t b e r e -d u c e d t h r o u g h t r a i n i n g . T h e t r a i n i n g w o u l d i n -v o l v e u s i n g t h e c h e c k l i s t to a n a l y z e v i d e o t a p e s o fs e v e r a l j o b s f o r w h i c h p o s t u r a l e x p o s u r e w a sk n o w n . C o m p a r i s o n o f th e c h e c k l i s t re s u l t s w i t ht h e s t a n d a r d r e s u l ts w o u l d i d e n t i f y a n a l y st -s p e c i fi c p r o b l e m s i n r e c o g n i z i n g p o s t u r e s o r e s t i-m a t i n g d u r a t i o n s . T h e s e p r o b l e m s c o u l d t h e n b ea d d r e s s e d .Sour ces con t r i bu t i ng t o check l i s t over es t i ma t i on o fa w k w a r d p o s t u r es

S e n s i ti v i ty w a s i m p o r t a n t t o m i n i m i z e t h en u m b e r o f p r o b l e m j o b s c l as s if ie d a s a c c e p t a -b l e ( f a l s e n e g a t i v e s ) . T o i n c r e a s e t h e s e n s it i v it y ,t h e a n a l y s t s w h o c o m p l e t e d t h e c h e c k l i s ts w e r ei n s t ru c t e d t o c h o o s e t h e l o n g e r d u r a t i o n c a t e g o r yo r t h e m o r e s e v e r e p o s t u r e c a t e g o r y ( e. g ., se v e r et r u n k f l e x io n v s. m i l d t r u n k f l e x io n ) in b o r d e r l i n ec a s e s . T h e s e i n s t r u c t i o n s w o u l d l e a d t o s o m eo v e r e s t i m a t i o n .Sour ces con t r i bu t i ng t o check l i s t under es t i ma t i ono f a w k w a r d p o s tu r e s

A s m e n t i o n e d i n t h e r e s u l t s s e c t i o n , u n d e r e s t i -m a t i o n o f t h e s t r e s s a s s o c i a t e d w i t h m i l d f le x i o na n d t w i st in g o r l a t e r a l b e n d i n g o f t h e n e c k o c -c u r r e d f o r a b o u t o n e - t h i r d o f t h e j o b s in t h ec o m p a r i s o n . T h i s u n d e r e s t i m a t i o n m a y h a v e b e e ni n f l u e n c e d b y t h e f o l l o w i n g f a c t o r s . F i r s t , i n t h ea n a l y s t t r a i n i n g , n e c k p o s t u r e w a s e m p h a s i z e d

l es s t h a n t r u n k p o s t u r e a n d e r g o n o m i c r i sk fa c -t o r s a s s o c i a te d w i t h u p p e r e x t r e m i t y c u m u l a t iv et r a u m a d i s o r d e r s . T h i s t r a i n i n g b i a s m a y h a v er e s u l te d i n le ss a w a r e n e s s a n d t h e r e f o r e u n d e r r e -p o r t i n g o f n e c k p o s t u r e s . S e c o n d , a w k w a r d n e c kp o s t u r e s u c h a s m i l d f le x i o n w a s v e r y c o m m o na c c o r d i n g t o i n f o r m a l f e e d b a c k f r o m t h e a n a ly s ts .B e c a u s e m i ld n e c k f l e x io n w a s b o t h c o m m o n a n dn o t p e r c i e v e d a s a s e r io u s e r g o n o m i c p r o b l e m ,t h e c h e c k l i s t u s e r s m a y h a v e b e e n u n r e s p o n s i v et o t h i s q u e s t i o n .Us er accep t ance

A l t h o u g h t h e a c c e p t a b i l i t y a n d e a s e - o f - u s e o ft h e c h e c k l i s t w e r e n e v e r f o r m a l l y e v a l u a t e d , s e v-e r a l i n t e r v i e w s w e r e h e l d w i t h c h e c k l i s t u s e r s t oe l ic i t c o m m e n t s a n d s u g g e s t io n s f o r c h a n g e . T h e s ei n t e r v i e w s r e v e a l e d t h a t , i n g e n e r a l , t h e c h e c k l i s tw a s w e l l a c c e p t e d . N e w u s e r s o f t h e c h e c k l is tf o u n d i t t o b e a u s e f u l t o o l f o r l e a r n i n g s p e c i f i cp o s t u r a l r i s k f a c t o r s . A s u s e r s g a i n e d e x p e r i e n c ep e r f o r m i n g e r g o n o m i c j o b e v a l u a t io n s , t h e c h e c k -l i s t s e r v e d a s a r e m i n d e r o r p r o m p t t o a s s u r e t h a ts o m e o f t h e m o r e s u b t l e r i sk f a c t o r s w e r e n o to v e r l o o k e d . S o m e u s e r s r e p o r t e d p r o b l e m s inc l as s if y in g p o s t u r e s i n t o n e u t r a l v s . n o n - n e u t r a lc a t e g o r i e s ( d u e t o t h e i n a b il it y t o d i r e c t l y m e a -s u r e jo i n t a n g l e s ) a n d i n e s t im a t i n g t h e d u r a t i o no f n o n - n e u t r a l p o s t u r e s . M a n y u s e r s w e r e f r us -t r a t e d b y t h e i n a b i l it y o f t h e c h e c k l i s t t o a s s o c i a t et h e p r e s e n c e o f r is k f a c t o rs ( c h e c k s a n d s t a r so n t h e f o r m ) w i t h s p e c i fi c w o r k a c t iv i ti e s. T h e s eu s e r s s u g g e s t e d t h a t t h e c h e c k l i s t b e m o d i f i e d toa l l o w t h e m t o m a k e s u p p l e m e n t a l n o t e s i n o r d e rt o i d e n t i f y t h e w o r k a c t i v i ti e s r e s p o n s i b l e f o r p o s -t u r a l r i s k f a c t o r s . T h i s i s a n o t h e r a r g u m e n t i nf a v o r o f d o c u m e n t i n g w o r k e r c h a r a c t e r i s t i c s a n dw o r k m e t h o d s a t th e t i m e o f d a t a c o l l e c t i o n . T h i sd o c u m e n t a t i o n w o u l d f a c i l i t a t e t h e c h e c k l i s t ' s u s ea s a d i a g n o s t i c a i d in d e t e r m i n i n g s p e c i f i c c a u s e so f e r g o n o m i c s t re s s.

A l t h o u g h t h e z e r o , c h e c k , s t a r s y st e mu s e d f o r r a t i n g s t r e s s e s i s n o t a u n i v e r s a l l y r e c o g -n i z e d s y s t e m o f o r d i n a l r a n k i n g , c h e c k l i s t u se r sr e p o r t e d n o p r o b l e m i n l e a r n i n g o r a p p l y i n g t h iss y s t e m . H o w e v e r , a l t e r n a t e r a n k i n g s y s t e m s s u c ha s g r e e n , y e l l o w , r e d o r 1 , 2 , 3 m a yb e m o r e i n t u i t i v e , p a r t i c u l a r l y f o r u s e r s w h o d on o t p a r t i c i p a t e i n a o n e - w e e k t r a i n i n g p r o g r a m .


16/19

298 W M Keyserling et al / Checklist fo r evaluating ergonomic risk factorsS u m m a r y

A o n e - p a g e c h e c k l is t f o r e v a l u a t in g e r g o n o m i cr is k fa c t o r s a s s o c i at e d w i t h a w k w a r d p o s t u r e s w a sd e v e l o p e d a n d e v a l u a t e d a s p a r t o f a j o i n t u n i o n -m a n a g e m e n t e r g o n o m i c s i n t er v e n ti o n p r o g r a m .T h i s c h e c k li s t w a s d e s i g n e d t o b e u s e d b y p e r s o n sw i t h l i m i te d e r g o n o m i c t r a in i n g a s a r a p i d s c r e e n -i n g to o l f o r i d e n t i f y in g j o b s w i t h e x p o s u r e s t oa w k w a r d p o s t u r e s . T h e c h e c k li s t w a s u s e d t o as -s e s s p o s t u r a l r i sk f a c t o r s o n 3 3 5 j o b s i n f o u rp l a n t s a n d w a s f o u n d t o b e a n e f f e c ti v e i n s tr u -m e n t f o r i d e n ti f y in g p o t e n t i a ll y h a r m f u l e x p o -s u r e s .

A c k n o w l e d g e m e n t s a n d d i s c la i m e rT h e a u t h o r s t h a n k M s . J u l i a n n L e o n a r d , M r .

A n d r e w B i g e lo w , a n d M s . L i s a M u r p h y f o r th e i ra s s i s t a n c e i n t h e c o l l e c t i o n a n d a n a l y s is o f d a t a .T h e a u t h o r s a ls o t h a n k t h e E r g o n o m i c C o o r d i n a -t o rs a n d E r g o n o m i c M o n i t o r s a t t h e p a rt i c ip a t i n gp l a n t s i te s f o r f a c i l i ta t i o n o f c o l l e c t io n o f i n - p l a n td a t a .

T h i s p r o j e c t w a s s u p p o r t e d b y j o i n t f u n d s f r o mt he U A W / G M N a t io n a l J o in t C o m m i t t e e o nH e a l t h a n d S a f e ty , w h i c h d o e s n o t n e c e s s a r il ys u p p o r t o r e n d o r s e t h e f in d i n g s h e r e i n a n d w h i c ha r e s o l e l y th e r e s p o n s i b i l i t y o f t h e a u t h o r s .

A p p e n d i x

E R G O N O M I C R I S K F A C T O R C H E C K L I S T F O R A W K W A R DP O S T U R E O F T H E L E GS T R U N K A N D N E C K

G e n e r a l B o d y P o s t u r e / L e g s1 . S t and ing s t a t i ona ry (no wa lk ing o r l e an ing)2 . U s i n g a f o o t p e d a l w h i le s t a n d i n g3 . L y ing on b ack o r s i de4 . Knee l ing5 . K n e e s b e n t o r s q u a t t i n g

n e v e r s o m e t i m e s > 1 / 3 c y cl e

o o , ~o ~ *o .~ *o / J *o ~ *

6 . S i t t i ng wi th back suppor t7 . S i t t i ng wi thou t back suppor t

n e v e r < 1 / 3 d a y > 1 / 3 d a yo o /,,Io ~,~ *

T r u n k P o s tu r e8 . M i l d f o r w a r d b e n d i n g ( > 2 0 )9 . S e v e r e f o r w a r d b e n d i n g ( > 4 5 )

1 0 . B a c k w a r d b e n d i n g ( > 2 0 )11 . T wis t i ng o r l a t e ra l bend ing (> 20 )

n e v e r s o m e t i m e s > 1 / 3 c y cl eo ~ *oo / I *o / J *

N e c k P o s t u r e1 2. M i l d f o r w a r d b e n d i n g ( > 2 0 )1 3. S e v e r e f o r w a r d b e n d i n g ( > 4 5 )1 4. B a c k w a r d b e n d i n g ( > 2 0 )15 . T wis t i ng o r l a t e ra l ben d ing (> 20 )To ta l Sco re = ( N o . o f * s ) ( N o . o f t f s )C o m m e n t s :

00 P *O P *0 t j *

J o b N u m b e r


17/19

W.M. Keyserling et aL / Checklist for evaluating ergonomic risk factors 299S U P P L E M E N T A L N O T E S F O R P O S T U R E C H E C K L I S T

Question1 . S t a n d i n g s t a t i o n a r y ( n o w a l k i n g o r l e a n i n g )

Standing T h e e n t i r e w e i g h t o f t h e b o d y i s s u p p o r t e d b y t h e w o r k e r s l eg s .Stationary T h e w o r k e r r e m a i n s i n a s t a n d i n g p o s t u r e w i t h o u t m o v i n g t h e l o w e r e x tr e m i t i e s .2 . U s i n g a f o o t p e d a l w h i l e s t a n d i n g

T h e w e i g h t o f t h e b o d y i s s u p p o r t e d b y o n e f o o t w h i l e t h e o t h e r f o o t o p e r a t e s a p e d a l .4 . K n e e l i n g

O n e o r t w o k n e e s t o u c h t h e g r o u n d .5 . K n e e s b e n t o r s q u a t t i n g

T h e i n c l u d e d a n g l e b e t w e e n t h e t h i g h a n d t h e c a l f is le s s t h a n 1 5 0

r u n k Posture

I N C L U D E D A N G L EB E T W E E NT H IG H A N D C A L F

F O R W A R D B E N D I N Gmild is 20* - 45 f rom vert icals v r is > 4 5 f rom vert ical

I

I i I z

L A T E RA L B E NDI NG T W IS T ING

Neck Posture

e f e r e n c e s

A a r a s , A . , W e s t g a a r d , R .H . a n d S t r a n d e n , E . , 1 9 8 8 . P o s t u r a la n g l e s a s a n i n d i c a t o r o f p o s t u r a l l o a d a n d m u s c u l a r i n j u r yi n o c c u p a t i o n a l w o r k s i t u a t i o n s . E r g o n o m i c s , 3 1 ( 6 ) : 9 1 5 -933.A g u a y o , A . J . , 1 9 7 5 . N e u r o p a t h y d u e t o c o m p r e s s i o n a n de n t r a p m e n t . I n : P . J . D y c k , P .K . T h o m a s a n d P .K . L a m b e r t( E d s . ) , P e r i p h e r a l N e u r o p a t h y . W . B . S a u n d e r s C o m p a n y ,P h i l a d e l p h i a , p p . 6 8 8 - 7 1 3 .

A n d e r s s o n , G .B . J . , 1 9 8 1 . E p i d e m i o l o g i c a s p e c t s o n l o w - b a c kpa in in indus t ry . Sp ine , 6 (1 ) : 53-60 .

A n d e r s s o n , G .B . J . , O r t e n g r e n , R . a n d H e r b e r t s , P . , 1 9 7 7 .Q u a n t i t a t i v e e l e c t r o m y o g r a p h i c s t u d i e s o f b a c k m u s c l ea c t iv i t y r e l a t e d t o p o s t u r e a n d l o a d i n g . O r t h o p e d i c C l i n ic so f N o r t h A m e r i c a , 8 ( 1 ): 8 5 - 9 6 .

A n d c r s s o n , B . J .G . , O r t e n g r e n , R . , N a c h e m s o n , A . a n d E l f -s t r o m , G . , 1 9 7 4a . L u m b a r d i s c p r e s s u r e a n d m y o e l e c r t i cb a c k m u s c l e a c t i v it y d u r i n g s i t ti n g I . S t u d i e s o n a n e x p e r i -m e n t a l c h a i r. S c a n d i n a v i a n J o u r n a l o f R e h a b i l i t a t io nMedic ine , 6 (3 ) : 104-114 .


18/19

300 W M Keyserling et aL / Checklis t for evaluating ergonomic r isk factors

Anders son, B.J.G., Ortengren, R., Nachemson, A. and Eif-strom, G., 1974b. Lumbar disc pressure and myoelectricback muscle activity during sitting IV. Studies on a cardriver's seat. Scandinavian Journal of RehabilitationMedicine, 6(3): 128-133.

Ariel, B.G., 1974. Biomechanical analysis of the knee jointduring deep knee bends with a heavy load. In: R.C. Nelsonand C.A. Morehouse (Eds.), Biomechanics IV. UniversityPark Press, Baltimore, MD, pp. 44-52.

Astrand, P.-O. and Rodahl, K., 1986. Textbook of work physi-ology. McGraw-Hill Book Co., New York.

Atha, J., 1984. Current techniques for measuring motion.Applied Ergonomics, 15(4): 245-257.

Boussenna, M., Corlett, E.N. and Pheasant, S.T., 1982. Therelationship between discomfort and postural loading atthe joints. Ergonomics, 25(4): 315-322.

Buckle, P.W., Stubbs , D.A. and Baty, D., 1986. Musculo-skeletal disorders (and discomfort ) and associated workfactors. In: E.N. Corlett, J. Wilson and I. Manenica (Eds.),The Ergonomics of Working Posture: Models, Methodsand Cases. Taylor and Francis, London, pp. 19-30.

Chaffin, D.B., 1973. Localized muscle fatigue - Defini tionand measurement. Journal of Occupational Medicine,15(4): 346-354.

Chaffin, D.B. and Andersson, G.B.J., 1984. OccupationalBiomechanics. John Wiley Sons, New York. Coffman,J.D., 1975. Diseases of the periphe ral veins. In: P.B.Beeson and W. McDermott (Eds.), Textbook of MedicineVol. II, 14th edition. W.B. Saunders Co., Philadelphia, pp.1083-1084.

Corlett, E.N., Madeley, S.J. and Manenica, I., 1979. Posturetargetting: A technique for recording working postures.Ergonomics, 22(3): 357-366.Corlett, E.N. and Bishop, R.P., 1978. The ergonomics ofspotwelders. Applied Ergonomics, 9(1): 23-32.

Corlett, E.N. and Bishop, R.P., 1976. A technique for assess-ing postural discomfort. Ergonomics, 19(2): 175-182.

Deverell, W.F. and Ferguson, J.H., 1968. An unusual case ofsciatic nerve paralysis. The Journal of the American Medi-cal Association, 205(10): 109-110.

Feldman, R.G., Goldman, R. and Keyserling, W.M., 1983.Peripheral nerve entrapment syndromes and ergonomicfactors. American Journal of Industrial Medicine, 4(5):661-681.

Gibbons, J.D., 1971. Non-Par ametric Statistical Inference.McGraw-Hill Book Co., New York, pp. 263-267.Grandjean, E., Hunting, W., Maeda, K. and Laubli, Th., 1983.Constrained postures at office workstations. In: T.O.Kvalseth (Ed.), Ergonomics of Workstation Design. But-terworths, London, pp. 19-27.

Hammarskjold, E., Ekholm, J. and Harms-Ringdahl, K., 1989.Reproducibility of work movements with carpenters' handtools. Ergonomics, 32(8): 1005-1018.Harms-Ringdahl, K., Ekholm, J., Schuldt, K., Nemeth , G. andArborelius, U.P., 1986a. Load moments and myoelectricactivity when the cervical spine is held in full flexion andextension. Ergonomics, 29(12): 1539-1552.

Harms-Ringdahl, K. and Ekholm, J., 1986b. Intensity andcharacter of pain and muscular activity levels elicited by

maintained extreme flexion position of the lower-cervical-upper-thoracic spine. Scandinavian Journal of Rehabilita-tion Medicine, 18(3): 117-126.

Hunting, W., Grandjean, E. and Maeda, K., 1980 . Con-strained postures in accounting machine operators. Ap-plied Ergonomics, 11(3): 145-149.

Joubert, M.J., 1972. Tarsal tunnel syndrome. South AfricanMedical Journal, 46(17): 507-508.

Karhu, O., Kansi, P. and Kuorinka, I., 1977. Correcting work-ing postures in industry: A practical metho d for analysis.Applied Ergonomics, 8(4): 199-201.

Keyserling, W.M., 1986. Postural analysis of the trunk andshoulders in simulated real time. Ergonomics, 29(4): 569-583.

Keyserling, W.M., 1990. Computer-aided posture analysis ofthe trunk, neck, shoulders and lower extremities. In: W.Karwowski, A.M. Genaidy and S.S. Asfour (Eds.), Com-puter -Aided Ergonomics. Taylor Francis, London, pp.261-272.Keyserling, W.M., Armstrong, T.J. and Punnett, L., 1991.Ergonomic job analysis: A structured approach for identi-fying risk factors associated with overexertion injuries anddisorders. Applied Occur. Environ. Hyg., 6(5): 353-363.

Keyserling, W.M., Bigelow, A.B., Brouwer, M.L. and Murphy,L.A., 1990. Ergonomic job analysis: Methods to identify,evaluate, and control exposures to risk factors in theworkplace. In: B. Das (Ed), Advances in Industrial Er-gonomics and Safety II. Taylor Francis, London, pp.963-970.

Keyserling, W.M., Stetson, D., Silverstein, B.S. and Brouwer,M.L., in press. A checklist for evaluating upper extremitycumulative trauma disorders. Ergonomics.

Kilbom, A. and Persson, J., 1987. Work technique and itsconsequences for musculoskeletal disorders. Ergonomics,30(2): 273-279.

Kilbom, A., Persson, J. and Jonsson . B.G., 1986a. Disorders ofthe cervicobrachial region among female workers in theelectronics industry. International Journal of IndustrialErgonomics, 1(1): 37-47.

Kilbom, A., Persson, J. and Jonsson, B., 1986b. Risk factorsfor work-related disorders of the neck and shoulder - withspecial emphasis on working postures and movements. In:E.N. Corlett, J. Wilson and I. Manenica (Eds.), The Er-gonomics of Working Posture: Models, Methods and Cases.Taylor Francis, London, pp. 44-53.

Koller, R.L. and Blank, N.K., 1980. Strawberry pickers' palsy.Archives of Neurology, 37(5): 320.

Maeda, K., Okazaki, F., Suenaga, T., Sakurai, T. and Taka-matsu, M., 1980. Low back pain related to bowing postureof greenhouse farmers. Journal of Human Ergology, 9(2):117-123.

Magnusson, M., Ortengren , R., Andersson , G.B.J., Pete rsen,I. and Sabel, B, 1987. An ergonomic study of work meth-ods and physical disorders among professional butchers.Applied Ergonomics, 18(1): 43-50.Magora, A., 1972. Investigation of the relation between lowback pain and occupation 3. Physical requirements: Sit-ting, standing and weight lifting. Industrial Medicine,41(12): 5-9.


19/19

W M Keyserling et aL / Checklist for evaluating ergonomic risk factors 301N a c h e m s o n , A . , 1 9 6 6 . T h e l o a d o n l u m b a r d i s k s i n d i f f e r e n t

p o s i t i o n s o f t h e b o d y . C l i n i c a l O r t h o p a e d i c s a n d R e l a t e dR e s e a r c h , 4 5 : 1 0 7 - 1 2 2 .

N i e b e l , B .W ., 1 9 88 . M o t i o n a n d T i m e S t u d y 8 t h E d i t i o n .I r w i n , H o m e w o o d , I L p p . 5 7 5 - 6 1 0 .

O c c u p a t i o n a l S a f e t y a n d H e a l t h A d m i n i s t r a t i o n ( O S H A ) ,1 9 9 0 . E r g o n o m i c s P r o g r a m M a n a g e m e n t G u i d e l i n e s f o rM e a t p a c k i n g P l a n t s . P u b l i c a t i o n N o . O S H A - 3 1 2 1 , U .S .D e p a r t m e n t o f L a b o r , W a s h i n g t o n , D C .

P a l u c h , R . , 1 9 89 . P h y s ic a l l o a d o f m u s c u l o s k e l e t a l s y s t e m a n ds i c k l e a v e s o f t h e m e t a l l u r g i c w o r k e r s . I n : A . M i t a l ( E d . ) ,A d v a n c e s i n I n d u s t r i a l E r g o n o m i c s a n d S a f e t y I . T a y l o ra n d F r a n c i s , L o n d o n , p p . 7 4 7 - 7 5 5 .

P r i e l , V .Z ., 1 9 7 4 . A n u m e r i c a l d e f i n i t i o n o f p o s t u r e . H u m a nFac to rs , 16(6) : 576-584 .

P u n n e t t , L . , F i n e , L . J . , K e y s e r l i n g , W .M . , H e r r i n , G .D . a n dC h a f f i n , D .B . , 1 9 9 1 . B a c k d i s o r d e r s a n d n o n n e u t r a l t r u n kp o s t u r e s o f a u t o m o b i l e a s s e m b l y w o r k e r s . S c a n d i n a v i a nJ o u r n a l o f W o r k , E n v i r o n m e n t a n d H e a l t h , 1 7: 3 3 7 - 3 4 6 .R y a n , G .A . , 1 9 8 9. T h e p r e v a l e n c e o f m u s c u l o - s k e l e t a l s y m p -t o m s i n s u p e r m a r k e t w o r k e r s . E r g o n o m i c s , 3 2 ( 4 ) : 3 5 9 - 3 7 1 .

S a n d h u , H .S . a n d S a n d h e y , B .S . , 1 9 7 6 . O c c u p a t i o n a l c o m p r e s -s i o n o f t h e c o m m o n p e r o n e a l n e r v e a t t h e n e c k o f t h ef i b u l a . T h e A u s t r a l i a n a n d N e w Z e a l a n d J o u r n a l o fSurgery , 46(2) : 160-1 63 .

S a t o , M . a n d T a n a k a , S . , 1 9 7 3 . P o s t u r a l e f f e c t o n t h e r e l a t i o nb e t w e e n o x y g e n c o n s u m p t i o n a n d h e a r t r a t e . J o u r n a l o fH u m a n E r g o l o g y , 2 ( 1 ) : 2 1 - 3 0 .

S p a a n s , F . , 1 9 7 0 . O c c u p a t i o n a l n e r v e l e s i o n s . I n : P . J . V i n k e na n d G .W . B r u y n ( E d s .) , H a n d b o o k o f C l i n ic a l N e u r o l o g y ,V o l . 7 : D i s e a s e s o f N e r v e s , P a r t 1 . A m e r i c a n E l s e v i e r P u b .C o . , I n c . , N e w Y o r k , p p . 3 2 6 - 3 4 3 .

S t a l h a m m a r , H .R . , L e s k i n e n , T .P . J . , K u o r i n k a , I .A .A . ,G a u t r e a u , M .H . J . a n d T r o u p , J .D .G . , 1 9 8 6 . P o s t u r a l , e p i -d e m i o l o g i c a l a n d b i o m e c h a n i c a l a n a l y s i s o f l u g g a g e h a n -

d l i n g i n a n a i r c r a f t l u g g a g e c o m p a r t m e n t . A p p l i e d E r -gonomics , 17(3) : 177-183 .

S te t son , D .S . , Keyser l ing , W.M., S i lve r s te in ,

a checklist for evaluating ergonomic risk factors resulting_2

Documents