Folding and Unfolding Manual Wheelchairs

ARTIC AR TICLE LE IN PR PRESS ESS

Applied Ergonomics 34 (2003) 571–579

Folding and unfolding manual wheelchairs: an ergonomic evaluation of health-care workers$ Heather A. Whitea, R. Lee Kirbyb,* a

b

School of Health and Human Fitness, Faculty of Health Professions, Dalhousie University, Halifax, NS, Canada Division of Physical Medicine and Rehabilitation, Faculty of Medicine, Dalhousie University, Rehabilitation Centre Site, Queen Elizabeth II Health Sciences Centre, 1341 Summer Street, Halifax, NS, Canada B3H 4K4 Received 15 February 2002; received in revised form 6 June 2003; accepted 15 June 2003

Abstract

The objective of this study was to test the hypotheses (i) that health-care workers vary greatly in the methods used to fold and unfold selected manual wheelchairs, and (ii) that many of the methods used include bent and twisted back postures that are known to be associated with a high risk of injury. We studied 20 health-care workers in a rehabilitation center. Subjects folded and unfolded two wheelchairs of cross-brace design, one with and one without a sling seat. As outcome measures, we used a questionnaire, time taken, visual analog scales of perceived exertion and back strain, folded width, videotape and Ovako Working Posture Analysis System (OWAS) back scores (1–4). Subjects used up to 14 different combinations of approach, hand placement and back posture to accomplish the tasks. The mean OWAS scores were in the 2.4–3.1 range and 49 (42%) of the 118 scores recorded were class 4 (back simultaneously ‘‘bent and twisted’’, considered to be associated with the highest risk of injury). We also observed methods that appeared to be safe and effective. Age, gender, profession, experience and seat condition did not generally influence the outcome measures. We conclude that health-care workers use a variety of methods to fold and unfold wheelchairs, many of which include bent and twisted back postures that may carry a risk of injury. Further study is needed to confirm this risk, to identify more ergonomically sound wheelchair designs and to develop better methods of carrying out the common and important task of folding and unfolding wheelchairs. r 2003 Elsevier Ltd. All rights reserved. Keywords: Ergonomics; Prevention; Low back pain; Health-care workers; Wheelchairs

1. Introduction Introduction

Jones and Sanford (1996) projected that there would be 2 milli million on wheelc wheelchai hairr users users in the United United States States in 2000. 200 0. The ability ability to fold fold a manual manual wheelcha wheelchair ir into into a narrow narrow position position for easier easier transport transport and storage storage is a popu popula larr desi design gn feat featur uree (De Deit itzz an and d Du Dudg dgeo eon, n, 19 1995 95;; Kirby,, 1997 Kirby 1997;; Coop Cooper, er, 1998 1998). ). The cross-b cross-brac racee design design (Fi Fig g. 1), inve invent nted ed by Herb Herber ertt Ever Everes estt and and Harr Harry y Jenn Jennin ings gs in 1932 1932 (Coop Cooper, er, 1998 1998)) and and now now avai availa labl blee from most wheelchair wheelchair manufacturers, manufacturers, is still the most commonly used by community wheelchair users and in the hospital and rehabilitation settings. $

Partial Partial funding funding was received received from the Worker Workers’ s’ Compensa Compensation tion Board of Nova Scotia. *Corresponding *Corresponding author. Tel.: +1-902-473-1268; +1-902-473-1268; fax: +1-902-473+1-902-4733204. E-mail address: [email protected] (R. Lee Kirby). 0003-6870/$0003-687 0/$- see front matter matter r 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0003-6870(03)00079-6

Altho Although ugh there there is an extens extensive ive litera literature ture on many many aspects aspects of wheelc wheelchai hairs rs and their use (e.g., (e.g., acute and overuse injuries of wheelchair users, wheelchair performance), mance), surpri surprisin singly gly little little attenti attention on has been been paid paid to wheelchair ergonomics. In a search of English-language articles cited by Medline from January 1, 1950 to June 1, 2003, we identified 123 articles in response to the search terms ‘‘wheelchair AND ergonomics’’ and 13 from the search terms ‘‘wheelchair AND folding’’, but none dealt spec specifi ifica call lly y with with the the task taskss of fold foldin ing g and and unfo unfold ldin ing g manual manual wheelc wheelchai hairs rs by people people other other than than wheelc wheelchai hairr user userss or the the asso associ ciat ated ed risk risk of inju injury ry.. The The repo report rted ed success rates for folding/unfolding manual wheelchairs, as a compon component ent of the Wheel Wheelcha chair ir Skills Skills Test, range from 5% to 88% for groups of wheelchair users, ablebodi bodied ed subj subjec ects, ts, occu occupa pati tion onal al ther therap apy y stud studen ents ts at differ different ent levels levels of traini training ng and untrai untrained ned caregi caregiver verss (Kir Kirby by et al. al.,, 200 2002, 2, 200 2003a, 3a, b; Coolen et al., 2002). 2002). The methods used were not reported.

ARTIC AR TICLE LE IN PR PRESS ESS 572

H.A. White, R. Lee Kirby / Applied Ergonomics 34 (2003) 571–579

Fig. 1. Cross-braced Cross-braced wheelchair, wheelchair, open (A) and folded (B).

Low Low back back pain pain (LBP (LBP)) acco accoun unts ts for for 33% 33% of all all comp compen ensa satio tion, n, 4.6 4.6 bill billio ion n doll dollar arss each each year year in the the United United States States (van Oort et al., 1990). 1990). The individua individuall risk factors for the development of LBP that have been explored in the literature include age, gender, anthropometri pometricc charac character terist istics ics,, physic physical al fitness, fitness, smokin smoking, g, psyc psycho holo logi gica call fact factor orss and and prev previo ious us hist histor ory y of LBP LBP (Bieri Biering-So ng-Sorensen, rensen, 1983 1983;; Agn Agnew, ew, 198 1987 7; Bur Burton ton and Cassidy, Cassi dy, 1992 1992;; Gar Garg g and Moo Moore, re, 199 1992 2; Kha Khali lill et al. al.,, 1993). 1993 ). The work-re work-relat lated ed risk risk factor factorss report reported ed includ includee heavy work and lifting, static work postures, postures, twisting and bending postures, vibration, perceived exertion and perceived back strain (Stubbs (Stubbs et al., 1983; 1983; Videman et al., 1984;; Snook, 1985; 1984 1985; Harber et al., 1985; 1985; Agnew, 1987; 1987; Burdor Bur dorff et al. al.,, 199 1991 1; McAt McAtamney amney and Corlet Corlett, t, 1992 1992;; Borens Bor enstei tein n et al. al.,, 199 1995 5). Health-care Health-care occupations occupations frequently quently require require bending, bending, twisting twisting and lifting lifting postures postures (Ha Harb rber er et al al., ., 19 1985 85;; Jensen Jensen,, 1987 1987;; McAta McAtamney mney and Corlett, 1992; 1992; Knibbe and Friele, 1996, 1996, Hignett, 1996; 1996; Woolfrey and Kirby, 1998; 1998; Cromie et al., 2000; 2000; Elford et al al., ., 20 2000 00;; Hu Huii et al al., ., 20 2001 01;; Da Daynar ynard d et al. al.,, 200 2001 1). Jensen Jen sen (19 (1987) 87) report reported ed that that health health-ca -care re occupa occupatio tions ns constituted 6 of the top 10 ranked occupations for the incidence of LBP. In clinical practice, we have noted that that many many health health-ca -care re workers workers approa approach ch the task task of folding and unfolding wheelchairs in an awkward and inefficient manner. Although there is no direct evidence, epidemiologic or otherwise, linking the wheelchair folding/unfolding task to LBP, the circumstantial evidence cited above led us to

believe that this was a topic that warranted investigation. The purpose of this study was to evaluate this task, in a prelim prelimina inary ry and predom predomina inantl ntly y descri descripti ptive ve way, way, testing the hypotheses (i) that health-care workers vary greatly in the methods used to fold and unfold manual wheelc wheelchai hairs rs and (ii) that that many many of the methods methods used used include bent and twisted back postures that are known to be associated with a high risk of injury.

2. Method Methodss

2.1. Subjects With their With their inform informed ed consen consent, t, we studie studied d 20 health health-care workers in a rehabilitation center. Because this was a preliminary descriptive study and the variability of the data was unknown, we chose not to use a power analysis to more formally estimate the sample size. In an effort to achiev achievee a hetero heterogen geneou eouss and repres represent entati ative ve group group of health health-ca -care re worker workerss who routin routinely ely deal deal with with wheelwheelchairs, chairs, we recruited recruited 5 nurses, nurses, 5 health-care health-care aids/porters, aids/porters, 5 occupa occupatio tional nal therap therapist istss and 5 physic physical al therap therapists ists.. There were 6 men and 14 women and the mean (7SD) age age was 32.8 2.8 (76.6 6.6)) years years (range (range 22– 22–45) 45).. Inclus Inclusion ion crit criteri eria a incl includ uded ed an age age rang rangee of 18–6 18–60 0 year yearss and and previous experience folding a wheelchair (at least once during the month prior to the study). We excluded any subject with current or recent LBP, arm pain or any other other contra contraind indica icatio tions ns to liftin lifting g (e.g., (e.g., uncont uncontrol rolled led

ARTIC AR TICLE LE IN PR PRESS ESS H.A. White, R. Lee Kirby / Applied Ergonomics 34 (2003) 571–579

hypert hypertens ension ion or heart heart diseas disease). e). Twent Twenty-th y-three ree people people volunteered for the study, but 3 were excluded because they they report reported ed curren currentt or recent recent LBP. The study was approv approved ed by the Resear Research ch Ethics Ethics Commit Committee tee of the Queen Elizabeth II Health Sciences Centre. 2.2. Wheelchairs The two wheelc wheelchai hairs rs (Everes (Everestt & Jennin Jennings, gs, Custom Custom Premier, 4203 Earth City Expressway, Earth City, MO 63045) that we used in this study were representative of those commonly used in both hospital and community setting settingss (Fi Fig. g. 1) (Dei Deitz tz and Dud Dudgeo geon, n, 199 1995 5; Cooper, 1998). 1998 ). The chairs were both cross-braced, folding chairs, each each weighi weighing ng 17. 17.9 9 kg. They They were were manual manually ly propel propelled led with rear-wheel drive, 60-cm-diameter rear wheels with pneumatic tires, 20-cm-diameter front casters with solid tires, high-mount push-to-lock wheel brakes, removable desk-length desk-length armrests, armrests, seat rails 48 cm from the floor and swinging, swinging, detachable, detachable, footrests footrests with heel loops. loops. The two wheelch wheelchair airss were were identi identical cal except except that that one had a sling seat while the other had the seat removed (the no-seat no-seat condition) condition).. We included included both conditions conditions because removable solid seating bases that attach to the seat rails are increasingly being prescribed to improve sitting posture and comfort and, without the sling seat to grasp, the person folding the wheelchair must grasp the seat rails or cross-brace to fold the wheelchair. We chose not to equip the no-seat wheelchair with a drop seat seat beca becaus usee we wish wished ed to focu focuss spec specifi ifical cally ly on the the folding and unfolding skills. The handling of wheelchair parts (e.g., drop seat, modular modular backrest, backrest, quick-rele quick-release ase rear rear wheels wheels), ), that that someti sometimes mes need to be remove removed d to break the wheelchair down into the smallest and lightest components components possible for transportat transportation ion or storage, storage, is sufficiently problematic that we considered it beyond the scope of the current study. 2.3. Procedure Subjects were oriented to the experimental setup and completed a brief questionnaire that elicited information on the subject’s age, gender and occupation. We also inquir inquired ed about about the subjec subjects’ ts’ experi experienc ence, e, traini training ng and previous injuries related to the tasks of folding/unfolding a manual cross-braced wheelchair. We posi positio tione ned d the the whee wheelc lcha hair irss on a smoo smooth th tile tiled d surface (commonly found in the health-care setting) with the the caste casters rs alig aligne ned d in the the rear rear-t -trai raili ling ng posi positi tion on (as (as though rolling forward). Pilot work had identified that the vertic vertical al force force ( 76 N) need needed ed to fold fold the the whee wheellchairs chairs varied dependin depending g on the floor surfac surfacee and the alignment of the casters, but we chose to standardize this for the purpose of this preliminary study. The wheelchair was positioned at a 45 angle to a single single videocam videocamera era located located 4 m away away from from the neares nearestt

573

rear wheel axle and 1 m above the floor. The videotape videotape data was to ensure that we captured relevant qualitative data, as well as providing data that could be coded and scored scored.. In their their starti starting ng positi positions ons,, subjec subjects ts faced faced the wheelchair at a 90 angle from the plane of view of the videocamera videocamera and behind behind a line 1.5 m from the right rear wheel wheel axl axle. e. A photoc photocell ell 1.22 m above above the floor sensed sensed the the moti motion on of the the subje subject ct movi moving ng past past the the line line and and triggered a photographic flash within the field of view of the videocamera. This was for the purpose of timing the tasks, an indirect measure of the subjects’ task efficiency. We asked subjects to fold the wheelchair to its tightest possible position, using their usual methods. Once the subj subjec ectt was was sati satisfi sfied ed,, he/s he/she he step steppe ped d back back over over the the starting line. Subjects were permitted to repeat any tasks that they considered considered unrepresentativ unrepresentativee of their routine practices. Also, subjects were asked to repeat the task if they forget to step back over the line upon completion of the task. To determine how well the folding task had been been comple completed ted,, we measure measured d the folded folded width width (RESNA,, 199 SNA 1998 8) of the the chai chairr (to (to the the near neares estt mm) mm) usin using g anthropomorphic calipers. We reported the width of the folded wheelchair as a percentage of the unfolded width. We then asked subjects to unfold the chair to its ‘ready to use’ position, using their usual methods. When the subject had completed these tasks with one wheelchair, he/she repeated the folding and unfolding tasks with the other other wheelc wheelchai hair. r. The order order of wheelc wheelchai hairs rs was ranrandomly assigned. 

2.4. Subjective perceptions In addition to the objective evaluations, we considered ered it impo importa rtant nt to obta obtain in data data on the the subj subjec ecti tive ve perc percep epti tion onss of the the subj subjec ects. ts. Afte Afterr the the subj subjec ects ts had had completed folding and unfolding both wheelchairs, they used used visual visual analog analogue ue scales scales (VAS) (VAS) to quanti quantify fy their their perceived exertion and perceived back strain (Ulin (Ulin et al., 1993). 1993 ). The VAS for the former was labeled ‘‘not at all difficult difficult or strenuous’’ strenuous’’ at 0 mm and ‘‘extremely ‘‘extremely difficult and strenuous strenuous’’ ’’ at 100 mm; mm; the latter was labele labeled d ‘‘no ‘‘no discomfort or strain experienced’’ experienced’’ at 0 mm and ‘‘extreme disc discom omfo fort rt and and stra strain in expe experi rien ence ced’ d’’’ at 100 100 mm. mm. We reported the subjects’ marks on the VASs as percentages of the distance distance from from 0 to 100 mm. mm. The VAS has been found found to be a val valid id and reliable reliable tool for quantifyi quantifying ng subjective perceptions (Huskisson (Huskisson et al., 1976; 1976; Scott and Huskisson, 1977; 1977; Guyatt et al., 1987). 1987). Subjects were also asked if they were satisfied with the methods that they used.

B



2.5. Data reduction We divided the videotape analysis into components, name namely ly fold foldin ing g and and unfo unfold ldin ing g the the foot footpl plat ates es of the the whee wheelc lcha hair ir (wit (with h the the slin sling g seat seat only only,, beca becaus usee the the



foot footpl plate atess were were iden identi tica call for for the the two two whee wheelc lcha hair irs), s), folding and unfolding the wheelchair with the sling seat, and folding and unfolding the wheelchair with the sling seat removed. The The vide videot otap apes es were were revi review ewed ed and and code coded d for for the the approa approach ch (side, (side, rear rear and/or and/or front) front),, the placem placement ent of each hand (on the armrest, push-handle, footplate, seat, seat rail and/or cross-brace), and the most risky back postur posturee observ observed ed (as defined defined by the Ov Ovako ako Worki Working ng Posture Analysis System [OWAS])(Karhu [OWAS])(Karhu et al, 1977; 1977; de Bruijn et al., 1998; 1998; Li and Buckle, 1999). 1999). The OWAS was originally reported by Karhu et al. (1977) and has been used in the study of health-care workers (Engels (Engels et al., 1994; 1994; Doormaal et al., 1995) 1995) and a variety of other settings. Although the OWAS is not a substitute for a detailed biomechanical analysis (Olen(Olendorf and Drury, 2001), 2001), we considered this tool to be approp appropria riate te for a prelim prelimina inary ry study study such such as this this one. one. The OWAS provides a means of classifying arm, leg and back back post postur ures es.. For For back back postu postures res (the (the focu focuss of this this study), class 1 postures (straight) are those that ‘‘do not need any special attention, except in special cases’’, class 2 postur postures es (bent) (bent) are those that that ‘‘ ‘‘mus mustt be consid considered ered during during the next next regula regularr check check of workin working g method methods’’ s’’,, clas classs 3 post postur ures es (twi (twiste sted) d) are are thos thosee that that ‘‘ ‘‘ne need ed conconsideration in the near future’’ and class 4 postures (bent and twisted) are those that ‘‘need immediate consideration’’. The times required to complete the tasks of folding and unfold unfolding ing the two wheelc wheelchai hairs rs were were determ determine ined d from from the the vide videot otap ape, e, usin using g a fram framee coun counte terr (30 (30 fps) fps).. Timing Timing began began with with the frame frame in which which the photoce photocell ll triggered the photographic flash and finished when the subject crossed the line at the completion of the task. In the few instances that the flash did not function, the starti starting ng time time was was defin defined ed as the the fram framee in whic which h the the subject’s subject’s shoulders shoulders passed the photocells photocells.. The videorvideorecorder malfunctioned for two subjects, reducing the n values for some measures.

at the effect of age, Mann–Whitney tests to evaluate the effects of gender and experience, Wilcoxon signed-rank tests to look at the effect of seat condition, and Kruskal– Willis tests to look at the effect of profession. Because there were 8 dependent measures and we looked at the sling-seat and no-seat conditions separately, we used the Bonferroni procedure to adjust the a level from 0.05 to 0.0031 0.0 0313 3 (0.05/ (0.05/16) 16) to elimin eliminate ate the effect effect of multip multiple le comparisons.

2.6. Statistical analysis

Subjects used a variety of combinations and permutations of approach, hand placement and back posture—7 meth method odss to fold fold and and 9 to unfo unfold ld the the foot footpl plat ates es,, 7 methods to fold and 14 to unfold the wheelchair with the sling seat, and 10 methods to fold and 7 to unfold the wheelchair with the seat removed.

We used used SAS softwa software re (versi (version on 6.1 6.12, 2, SAS SAS Institu Institute te Inc. Inc.,, SAS SAS Camp Campus us Driv Drive, e, Cary Cary,, NC 2751 27513) 3) for for the the statistical analysis. Descriptive statistics were generated. We also compared folding time with unfolding time and the the sl slin ingg-se seat at vs no-s no-sea eatt cond condit itio ions ns usin using g twotwo-wa way y repeate repeated d measur measures es ANOVA ANOVA,, after after perfor performin ming g a log transformation of the data. Although not the primary purpos purposee of the study, study, we evalua evaluated ted the effects effects that 5 independent measures (age, gender, profession, experience [at least daily vs less frequently] and seat condition [sling seat vs no seat]) had on the 8 outcome (dependent) measures (folding and unfolding times, perceived exertion, tion, percei perceived ved back back strain, strain, folded folded width width and OW OWAS AS scores). We used Spearman correlation analysis to look

3. Results Results

3.1. Questionnaire Eleven (55%) of the 20 subjects reported completing the task of folding/unfolding a wheelchair at least once a day, with frequencies ranging up to 30 times in a day. The other 9 (45%) subjects reported completing the task with frequencies ranging from 3 to 4 times per week to once once a month. month. In answer answer to the question question about about how subjects learned to fold/unfold a wheelchair, of the 27 responses responses to this question (some subjects included more than one), 12 (44%) responses were ‘‘self-taught or trialand-error process’’, 6 (22%) were ‘‘formal education at physiotherapy or occupational therapy school’’, 5 (19%) were ‘‘informal teaching by colleagues’’, 3 (11%) were ‘‘taught by an occupational therapist’’ and 1 (4%) was taught taught ‘‘by ‘‘by the (hospi (hospital tal)) wheelc wheelchai hairr coordi coordinat nator’ or’’. ’. None of the subjects reported ever having been acutely injured while folding or unfolding a wheelchair. Fourteen (70%) of the subjects reported that their responsibilities included educating community caregivers about foldin folding g and unfold unfolding ing wheelc wheelchai hairs. rs. Sixtee Sixteen n subjec subjects ts (80%) reported satisfaction with their current methods of folding folding and unfolding unfolding wheelchairs. wheelchairs. 3.2. Method Method variations variations

3.3. Approach Approach directions directions The The side side approa approach ch was the most most common common overal overall, l, followed by the front approach when folding/unfolding the footpl footplate atess and the rear rear approa approach ch when when foldin folding/ g/ unfold unfolding ing the wheelc wheelchai hairs rs themse themselve lves. s. On averag average, e, subjects used more than one approach to complete the tasks and one subject used 5.


3.4. Handholds Handholds Of the the whee wheelc lcha hair ir parts parts used used as hand handho hold lds, s, the the footplates themselves were always grasped when folding/un ing/unfol foldin ding g them; them; the armrest armrestss were were the next next most most common commonly ly used. used. For foldin folding g the wheelc wheelchai hairr with with the sling sling seat, seat, the seat was the most most commo common n handho handhold, ld, wher wherea eass the the armr armres ests ts and and seat seat rail railss tied tied as the the most most common common handho handholds lds when when unfold unfolding ing this this wheelc wheelchai hair. r. For both folding and unfolding the wheelchair with no seat seat,, the the seat seat rail railss were were the the most most comm commonl only y used used,, followed by the armrests. 3.5. Footplates Footplates When dealing with the footplates, all but one subject flipp flipped ed them them up to allo allow w fold foldin ing; g; the the othe otherr subj subjec ectt swung them away. The most common method (13 [72%] of 18 subjects when folding the footplates and 15 [83%] when when unfol unfoldi ding ng them them)) was was for for the the subj subjec ectt to stan stand d beside the wheelchair with one hand on an armrest, then bend over with the back twisted and the legs straight or slightly bent to manipulate the footplates with the other hand. On 5 occasions (28%) while folding the footplates and 1 (6%) while unfolding them, the subjects crouched in front of the wheelchair. On 2 occasions (12%), a foot was used to unfold the footplates. 3.6. Folding Folding the wheelchair wheelchairss To successfully initiate folding the wheelchair with the sling seat, all 19 subjects grasped the sling seat and lifted (with the hands at both the front and back edges in 17 [90%] and the remaining 2 [10%] with a hand at the front front edge edge only). only). To comple complete te the foldin folding, g, 3 subjec subjects ts (16%) pushed the armrests together and 3 pushed the push-handles together. To initiate folding of the wheelchair with the sling seat remove removed, d, 10 (53%) (53%) of 19 subjec subjects ts lifted lifted one or both both seat rails. One subject pinched her fingers between the seat rail and clothing guard when folding the chair in this manner. Six other subjects (32%) lifted one or both upper upper arms arms of the cross-b cross-brac race. e. Seven Seven subjec subjects ts (37%) (37%) completed the fold by squeezing the armrests together, 3 (16%) squeezed the push-handles together and 2 (11%) squeezed the seat rails together. One subject approached the wheelchair from the side, used a hand on a pushhandle to tilt the wheelchair towards him, initiated the fold by pulling on the cross-brace with the other hand and then allowed gravity to complete the fold. 3.7. Unfolding Unfolding the wheelchairs wheelchairs To initiate unfolding of the wheelchair with the sling seat seat,, 8 (44% (44%)) of the the 18 subj subjec ects ts pull pulled ed the the armr armres ests ts apart, 5 (28%) pulled the push-handles apart (in 2 cases,

575

the subjects lifted the rear wheels slightly off the ground first first), ), 3 (17% (17%)) push pushed ed down down on the the seat seat rail railss and and 2 (11%) pushed on one push-handle and the opposite seat rail or armrest. To complete the unfolding, 9 subjects (50% (50%)) pushe pushed d down down on the the slin sling g seat seat and and 4 (22% (22%)) pushed down on the seat rails. To initiate unfolding of the wheelchair with the sling seat seat remov removed ed,, 9 (47% (47%)) of the the 19 subj subjec ects ts pull pulled ed the the armrests apart, 7 (37%) pulled the push-handles apart (in 5 cases, having lifted the rear wheels slightly off the floor), 1 (5%) pushed down on the seat rails and 1 (5%) pushed pushed on one push-h push-hand andle le and the opposi opposite te crosscrossbrace. brace. To comple complete te the unfold unfolding ing,, 6 subjec subjects ts (32%) (32%) pushed down on the seat rails and 6 pushed down on the cross-braces. 3.8. Outcome Outcome measures These results are summarized in Table 1. 1. The mean OWAS scores were in the 2.4–3.1 range and 49 (42%) of the the 118 118 scor scores es reco record rded ed were were clas classs 4. For For fold foldin ing/ g/ unfolding the footrests (not shown in Table 1) 1) (n ¼ 18), the the mean mean (7SD) SD) OW OWAS AS scor scoree was was 3.1 3.1 (71.1 1.1), ), the median 4 and the range 1–4. The folding times for the wheelchairs with and without the sling seat were 13 s and the mean mean unfold unfolding ing times times were were in the 9–1 9–15 5 s range range (not significantly significantly different). different). The median VAS scores for perceived exertion and back strain were all o15% of the dist distan ance ce from from 0–10 0–100 0 mm (bes (bestt to wors worst). t). The The mean mean folded widths were o50% of the unfolded widths. B

3.9. Effect Effect of independent independent variables There were no significant influences on the outcome (dependent) measures due to the independent measures (age, gender, profession, experience or seat condition), except except that that subjec subjects ts requir required ed signifi significan cantly tly less less time time to unfo unfold ld the the whee wheelc lcha hair ir with with the the slin sling g seat seat remo remove ved d ( p ¼ 0:00002).

4. Discussion Discussion

Desp Despite ite some some simi simila lari riti ties es of appr approa oach ch,, the the stud study y corroborated corroborated the hypotheses hypotheses that health-care health-care workers vary var y greatl greatly y in the methods methods used used to fold fold and unfold unfold manual wheelchairs and that many of the methods used include bent and twisted back postures associated with a high high risk risk of injury injury.. The study study also also yielde yielded d intere interestin sting g descriptive and qualitative information on the methods used. Some participan participants ts completed completed the folding/un folding/unfoldi folding ng tasks as often as 30 times a day. There were a number of ways that participan participants ts reported reported learning learning how to fold/ unfold a manual wheelchair, but the majority of them report reported ed learni learning ng throug through h a trial-a trial-andnd-err error or proces process. s.



Table 1 Folding and unfolding manual wheelchairs by health-care workers Wheelchair with sling seat

Wheelchair with no seat

n

Fold

n

Unfold

n

Fold

n

Unfold

Back posture (OWAS)a

19

Mean 2.4 SD 0.8 Median 2.0 Range 2.0–4.0

18


19


19


Time (s)

19


18


19


19


Perceived exertion (%) b

20

Mean 11.9 SD 14.0 Median 4.2 Range 0–47.3

20


Perceived back strain (%) b

20

Mean 9.1 SD 12.3 Median 4.4 Range 0–45

20


Folded width (%)c

20

Mean 47.5 SD 6.4 Median 45.7 Range 42.8–71

20


a

Ovako Working Posture Analysis System (OWAS) scores (1–4). Percentage Percentage of distance from 0 to 100 mm (from best to worst) on a visual analog scale. c Percentage of unfolded width. b

Ideally, the operation of a well-designed product should be intu intuit itiv ivee and and self self-e -evi vide dent nt.. When When good good desi design gn is insufficient to ensure safe operation, as seems to have been the case for the wheelchair designs that we studied, one comple complemen mentar tary y approa approach ch would would be more more formal formal ergonomics training about the task during professional education (Engels (Engels et al., 1998; 1998; Johnsson et al., 2002). 2002). None None of the partici participan pants ts reporte reported d learni learning ng from from an owne owner’ r’ss manu manual al for for a whee wheelc lcha hair ir.. Give Given n that that such such manuals are easily misplaced by users and that healthcare care prof profess essio iona nals ls may may not not see the the manu manual als, s, bett better er labeling of the wheelchair with instructions may be a more effective effective approach. approach. Given our small sample size, it was not surprising that none of the study participants had been acutely injured during during the task task of foldin folding g or unfold unfolding ing a wheelc wheelchai hair. r. This This coul could d have have been been beca becaus usee the the inci incide denc ncee of such such injuries is low. Alternatively, given that the magnitudes of perceived exertion and back strain that our subjects reported were low, any risk of LBP that they incurred due due to the the fold foldin ing/ g/unf unfol oldi ding ng task taskss coul could d be due due to ‘‘cumu ‘‘cumulat lative ive trauma trauma’’. ’’. Althou Although gh the etiolo etiology gy of LBP remains unclear in many cases, one theory is that LBP is the cumula cumulativ tivee effect effect of a number number of minor minor painle painless ss inju injuri ries es whic which h even eventu tual ally ly resu result lt in pain pain (Biering-

Sorensen, 1983 Sorensen, 1983;; Gar Garg g and Moore, Moore, 199 1992 2; Knib Knibbe be and Friele Fri ele,, 199 1996 6; Hign Hignett, ett, 1996 1996;; Da Dayn ynar ard d et al al., ., 20 2001 01). ). Biering-Sorensen (1983), (1983), for instance, found that about half of the people surveyed reported a gradual onset of LBP. LBP. It is theref therefore ore concei conceivab vable le (but, (but, by no means, means, proven) that improperly folding or unfolding a wheelchair could contribute to the development of LBP. The The OW OWAS AS scor scores es were were in the the moder moderat atee-to to-h -hig igh h range, range, suggesting suggesting the need to explore explore different different wheelchair designs (as noted earlier) or alternate methods for folding and unfolding wheelchairs that carry with them a lower risk of back injury. We are optimistic about the success of the latter because we observed examples of methods that appeared to be both safe and effective. To mini minimi mize ze the the risk risk of back back inju injury ry,, the the most most ergono ergonomic micall ally y sound sound method method (by which which we mean mean the method that minimized bent and twisted back postures (Karhu et al., 1977)) 1977)) that we observed for folding and unfolding the footplates was the crouch method (Fig. (Fig. 2). 2). This method was used by 5 subjects in our study to fold the the foot footpl plat ates es and and 1 to unfo unfold ld them them.. In the the crou crouch ch method, the subject approaches the chair from the front or side side,, rest restss one one hand hand on the the armr armres estt or seat seat for for balance, does a complete knee bend and uses the other hand hand to mani manipu pula late te the the foot footpl plat ates es to the the upri uprigh ghtt


577

Fig. 2. Folding and unfolding unfolding footplates with the crouch method.

Fig. 4. Unfolding a wheelchair wheelchair with the rear-lift method.

Fig. 3. Folding a wheelchair wheelchair with the side-tip method.

position. With this method, there is no need to bend or twist twist the back (i.e., (i.e., an OW OWAS AS score score of 1). Although Although safer, this method requires more time and energy than the bending-over method. To fold the wheelchair, the side-tip method (Fig. (Fig. 3) 3) appeared to be the most ergonomically sound. None of

the subjects used this method for folding folding the wheelchair wheelchair with the sling seat but one subject used this method for folding the wheelchair with the sling seat removed. In the side-ti side-tip p method method,, the subjec subjectt approa approache chess the chair chair from the side. The subject places the rear hand on the near-si near-side de push-h push-hand andle, le, bends bends straigh straightt forwar forward d and places the front hand on either the front edge of the sling seat or, if the sling seat has been removed, on the near-si near-side de seat seat rail. rail. Althou Although gh the subjec subjectt must must bend bend forward (i.e., an OWAS score of 2), the method does not require the subject to twist the back. The subject then tilts the wheelchair towards him/herself. This eliminates the fricti frictiona onall force force (that (that resist resistss wheelc wheelchai hairr foldin folding) g) between the far-side rear wheel and the floor. Once the far-side wheels are off the ground, pulling upwards on the sling upholstery or the seat rail initiates the fold and gra gravity vity com complet pletes es it. it. If the the sea seat rai rail is used used as a handho handhold, ld, the fingers fingers should should be remove removed d quickl quickly y to preven preventt pinchi pinching, ng, but a foldin folding g strap strap would would obviat obviatee this this risk. risk. Once Once the wheelc wheelchai hairr is comple completel tely y folded folded,, the user tilts the chair back so that all wheels rest on the floor. The The most most ergo ergono nomi mica call lly y soun sound d meth method od that that we obse observ rved ed for for unfo unfold ldin ing g a whee wheelc lcha hair ir was was the the rear rear-li lift ft meth method od (Fi Fig. g. 4). Two subjec subjects ts for the slingsling-seat seat



wheelc wheelchai hairr and 5 subjec subjects ts for the no-sea no-seatt wheelch wheelchair air used this method. In the rear-lift method, the subject approa approaches ches the chair chair from from the rear, rear, gra grasps sps the pushhandles, lifts the rear wheels slightly off the floor and pulls pulls the push-h push-hand andles les apart. apart. Liftin Lifting g the rear rear wheels wheels enables the user to eliminate the frictional force between the floor and rear wheels. The caster wheels swivel and then then roll roll in respon response se to the fricti frictiona onall forces forces affecti affecting ng them. The user need not bend or twist the back (i.e., an OWAS score of 1). However, wheelchairs with seat-rail clips clips or sticky sticky cross-b cross-brac racee articu articulat lation ionss requir requiree the subjec subjectt to lean straig straight ht forwar forward d with with one hand on a push-handle for balance and to use the other hand to exert a downward force on the seat rails (i.e., an OWAS score of 2). Although the methods described above are promising, further further testing will be needed to determine whether they are effecti effective, ve, efficie efficient nt and decrea decrease se the risk risk of injury injury associated with wheelchair handling. Other limitations of the study include the small sample size studied. The genera generall lack lack of influen influence ce of age, age, gender gender,, profess profession ion,, experience and seat condition on the outcome measures may may have have been been due due to the the smal smalll samp sample le si size ze.. Othe Otherr limitations include the single wheelchair design studied, the the use use of the the OW OWAS AS rath rather er than than a more more deta detail iled ed biomechani biomechanical cal analysis, analysis, studying studying the narrowly narrowly defined task that we did (rather than including related tasks, like the removal of drop seats, modular backrests and rear wheels), confining the study condition to a single floor surface, and limiting our study population to health-care professiona professionals ls (whereas (whereas hospital hospital volunteers volunteers and nonprononprofessional caregivers are also frequently called upon to fold and unfold unfold wheelchair wheelchairs). s). Despite these caveats and the need for further study, this is the first study to provide data about the methods used by health-care workers to fold and unfold manual wheelchairs.

5. Conclusion Conclusion

Health-care workers use a variety of methods to fold and unfold unfold wheelc wheelchai hairs, rs, many many of which which includ includee bent bent and and twis twiste ted d back back post postur ures es that that may may carr carry y a ri risk sk of injury. Further study is needed to confirm this risk, to identify more ergonomically sound wheelchair designs and and to deve develo lop p bette betterr meth method odss of carr carryi ying ng out out the the common and important task of folding and unfolding wheelchairs.

Acknowledgements

We thank Dr. John McCabe, Dr. John Kozey, Dr. Biman Das, Mr. Don MacLeod, Mr. Wade Blanchard and Mr. Darrin Smith for their help.

References Agnew, Agnew, J., 1987. Back pain in hospital hospital workers. workers. In: Emmett, Emmett, E.A. (Ed.), (Ed.), Health Health Problems Problems of Health Health Care Workers Workers.. Occupati Occupationa onall Medicine: State of the Art Reviews 2, 609–614. Biering-Sorensen, F., 1983. A prospective study of low back pain in a general population: occurrence, occurrence, recurrence recurrence and aetiology. Scand. J. Rehab. Med. 15, 71–79. Borenstein, D.G., Weisel, S.W., Boden, S.D., 1995. Low back pain: medical diagnosis and comprehensive management. WB Saunders, Philadelphia. Burdorf, A., Govaert, G., Elders, L., 1991. Postural load and back pain pain of workers workers in the manufac manufacturi turing ng of prefabri prefabricate cated d concrete concrete elements. Ergonomics 34, 909–918. Burton, Burton, C.V., C.V., Cassidy Cassidy,, J.D., J.D., 1992. 1992. Economi Economics, cs, epidemi epidemiolog ology y and ris risk k factors. factors. In: Burton, Burton, C.V., C.V., Kirkaldy Kirkaldy-Wil -Willis lis,, W.H. W.H. (Eds.), (Eds.), Managin Managing g Low Back Pain, Pain, 3rd Edition. Edition. Churchil Churchill-Li l-Living vingston stone, e, New York. Coolen, Coolen, A.L., A.L., Kirby, Kirby, R.L., R.L., Landry, Landry, J., MacPhee MacPhee,, A.H., A.H., Smith, Smith, C., MacLeod, D.A., 2002. Educating students of occupational therapy about wheelchair use: comparison comparison between standard curriculum and skill-acquisition skill-acquisition protocols. Proceedings of the RESNA 25th International International Conference, Minneapolis, Minneapolis, MN, June 27–July 1, 2002. RESNA Press, New York, pp. 261–263. Cooper, R.A., 1998. Wheelchair Selection and Configuration. Demos Medical Publishing Inc., New York, p. 3. Cromi Cromie, e, J.E., J.E., Rober Robertso tson, n, V.J., V.J., Best, Best, M.O., M.O., 2000. 2000. WorkWork-re relat lated ed musculo musculoskel skeletal etal disorder disorderss in physical physical therapis therapists: ts: prevalen prevalence, ce, severity, risks, and responses. Phys. Ther. 80, 336–351. Daynard, Daynard, D., Yassi, A., Cooper, J.E., Tate, R., Norman, Norman, R., Wells, R., 2001. Biomechanical analysis of peak and cumulative spinal loads during during simulat simulated ed patient-h patient-handl andling ing activiti activities: es: a substudy substudy of a randomized controlled trial to prevent lift and transfer injury of health care workers. Appl. Ergon. 32, 199–214. de Bruijn, Bruijn, I., Engels, Engels, J.A., van der Gulden, Gulden, J.W.J., J.W.J., 1998. A simple simple method to evaluate the reliability of OWAS observations. Appl. Ergon. 29, 281–283. Deitz Deitz,, J., J., Dudge Dudgeon, on, B., B., 1995. 1995. Wheel Wheelcha chair ir select selection ion proces process. s. In: Trombley, Trombley, C. (Ed.), Occupational therapy for physical dysfunction, 4th Edition. Williams & Wilkins, Baltimore, MD. Doormaal, Doormaal, M.T.A.J., Driessen, A.D.A., Landerweerd, Landerweerd, J.A., Drost, M.R., M.R., 1995. 1995. Physical Physical workload workload of ambulan ambulance ce assistan assistants. ts. ErgoErgonomics 38, 361–376. Elford, W., Straker, L., Strauss, G., 2000. Patient handling with and without slings: an analysis of the risk of injury to the lumbar spine. Appl. Ergon. 31, 185–200. Engel Engels, s, J.A., J.A., Lande Landerwe rweer erd, d, J.A., J.A., Kant, Kant, Y., Y., 1994. 1994. An OW OWASASbased based analy analysis sis of nurses nurses’’ workin working g postur postures es.. Ergon Ergonom omics ics 37, 909–914. Engel Engels, s, J.A., J.A., van der Gulde Gulden, n, J.W.J. J.W.J.,, Senden Senden,, T.F., T.F., Kolk, Kolk, J.J., J.J., Binkhorst, Binkhorst, R.A., 1998. The effects of an ergonomic-educati ergonomic-educational onal course—postural load, perceived physical exertion, and biomechanical nical errors errors in nursing. nursing. Int. Arch. Arch. Occup. Occup. Environ Environ.. Health Health 71, 336–342. Garg, A., Moore, J.S., 1992. Prevention strategies and the low back in industry. In: Moore, J.S., Garg, A. (Eds.), Ergonomics: Low Back Pain, Carpel Tunnel Syndrome and Upper Extremity Disorders in the Workplace. Occup. Med. State of the Art Rev. 7, 629–640. Guyatt, Guyatt, G.H., Townsend Townsend,, M., Berman, Berman, L.B., L.B., Keller, Keller, J.L., J.L., 1987 1987.. A compari comparison son of Likert Likert and visual visual analogu analoguee scales scales for measuri measuring ng change in function. J. Chron. Dis. 40, 1129–1133. Harber, P., Billet, E., Gutowski, M., SooHoo, K., Lew, M., Roman, A., 1985. Occupational low-back pain in hospital nurses. J. Occup. Med. 27, 518–524. Hignett, S., 1996. Work-related back pain in nurses. J. Adv. Nurs. 23, 1238–1246.

ARTIC AR TICLE LE IN PR PRESS ESS H.A. White, R. Lee Kirby / Applied Ergonomics 34 (2003) 571–579 Hui, L., Ng, G.Y., Yeung, S.S., Hui-Chan, C.W., 2001. Evaluation of physiolo physiologica gicall work demands demands and low back neuromus neuromuscula cularr fatigue fatigue on nurses nurses working working in geriatri geriatricc wards. wards. Appl. Appl. Ergon. Ergon. 32, 479–483. Huskisso Huskisson, n, E.C., E.C., Jones, Jones, J., Scott, Scott, P.J., P.J., 1976 1976.. Applicati Application on of visualvisualanalog analogue ue scales scales to the meas measure ureme ment nt of functi function onal al capaci capacity. ty. Rheumatol. Rehab. 15, 185–187. Jensen, R., 1987. Disabling back injuries among nursing personnel: research needs and justification. Res. Nurs. Health 10, 29–38. Johnsson Johnsson,, C., Carlsson Carlsson,, R., Lagerstr Lagerstrom, om, M., 2002. 2002. Evaluat Evaluation ion of training in patient handling and moving skills among hospital and home care personnel. Ergonomics 45, 850–865. Jones, M.L., Sanford, J.A., 1996. People with mobility impairments in the United States today and in 2010. Assistive Technol. 8, 43–53. Karhu, O., Kansi, P., Kuorinka, I., 1977. Correcting working postures in industry: a practical method for analysis. Appl. Ergon. 8.4, 199– 201. Khalil, T.M., Abdel, E.M., Moty Rosomoff, R.S., Rosomoff, H.L., 1993. 1993. Ergono Ergonomi mics cs in Back Back Pain: Pain: a Guid Guidee to Preve Preventi ntion on and and Rehabilitation. Van Nostrand Reinhold, New York. Kirby, R.L., 1997. Principles of wheelchair design and prescription. prescription. In: Lazar Lazar,, R.B. R.B. (Ed.), (Ed.), Princ Principl iples es of Neuro Neurolog logic ic Rehabi Rehabilit litati ation on.. McGraw-Hill, New York, NY, pp. 465–481 (Chapter 27). Kirby, R.L., Swuste, J., Dupuis, D.J., MacLeod, D.A., Monroe, R., 2002. Wheelchair skills test: pilot study of a new outcome measure. Arch. Phys. Med. Rehab. 83, 10–18. Kirby, R.L., Dupuis, D.J., MacPhee, A.H., Coolen, A.L., Smith, C., Best, Best, K.L., K.L., Newton, Newton, A.M., A.M., Mountain Mountain,, A.D., A.D., MacLeo MacLeod, d, D.A., D.A., Bonapar Bonaparte, te, J.P., J.P., 2003 2003a. a. The wheelcha wheelchair ir skills skills test (version (version 2.4): measurement properties. Arch. Phys. Med. Rehab. (in press). Kirby, Kirby, R.L., R.L., Thibaul Thibault, t, D., Mifflin, N., Smith, Smith, C., MacLeod MacLeod,, D.A., D.A., 2003b. 2003 b. Manual Manual wheelcha wheelchair-h ir-hand andling ling skills skills of caregiv caregivers ers:: effect effect of a wheel wheelcha chair ir skills skills traini training ng progra program. m. Proce Proceedi edings ngs of the RESNA 26th International Conference, Atlanta GA, June 19–23, 2003.

579

Knibb Knibbe, e, J.J., J.J., Friel Friele, e, R.D. R.D.,, 1996. 1996. Preva Prevalen lence ce of back back pain pain and characte characteris ristics tics of the physical physical workload workload of commun community ity nurses. nurses. Ergonomics Ergonomics 39, 186–198. 186–198. Li, G.Y., Buckle, P., 1999. Current techniques for assessing physical exposure to work-related musculoskeletal risks, with emphasis on posture-based methods. Ergonomics 42, 674–695. McAtamney, McAtamney, L., Corlett, E.N., 1992. Ergonomic Ergonomic workplace assessment in a health care context. Ergonomics 35, 965–978. Olendorf, M.R., Drury, C.G., 2001. Postural discomfort and perceived exertion exertion in standard standardized ized box-hold box-holding ing postures postures.. Ergonom Ergonomics ics 44, 1341–1367. RESNA, 1998.American 1998.American National Standard for Wheelchairs—vol. Wheelchairs—vol.1: 1: Requirem Requirements ents and Test Methods Methods for Wheelch Wheelchair airss (includi (including ng scooters). Rehabilitation Rehabilitation Engineering Engineering and Assistive Technology Society of North America Inc., New York. Scott, J.P., Huskisson, E.C., 1977. Measurement Measurement of functional functional capacity with visual analogue scales. Rheumatol. Rehab. 16, 257–259. Snook, Snook, S.H., S.H., 1985. 1985. Psychoph Psychophysi ysical cal consider consideratio ations ns in permissa permissable ble loads. Ergonomics 28, 327–330. Stubbs, D.A., Buckle, P.W., Hudson, M.P., Rivers, P.M., Worrington, Worrington, C.J., 1983. Back pain in the nursing profession: epidemiology and pilot methodology. Ergonomics 26, 755–765. Ulin, Ulin, S.S., S.S., Armstron Armstrong, g, T.J., T.J., Snook, Snook, S.H., S.H., Keyserl Keyserling, ing, W.M., W.M., 1993 1993.. Perceived Perceived exertion and discomfort associated with driving screws at vario various us work work locati location onss and at differ different ent work work frequ frequenc encies ies.. Ergonomics Ergonomics 36, 833–846. 833–846. van van Oort, Oort, G., G., Freder Frederick ick,, M., M., Pinto, Pinto, D., D., Rag Ragone one,, D., D., 1990 1990.. Back Back injuries require integration of aggressive aggressive and passive treatment. Occup. Health Saf. 59, 22–24. Videman, T., Nurminen, T., Tola, S., Kuorinka, I., Vanharanta, H., Troup, J.D.G., 1984. Low back pain in nurses and some loading factors of work. Spine 9, 400–404. Woolfrey, P.G., Kirby, R.L., 1998. Ergonomics Ergonomics in rehabilitation: rehabilitation: a comparison of two methods of moving an empty manual wheelchair short distances. Arch .Phys. Med. Rehab. 79, 955–958.

Folding and Unfolding Manual Wheelchairs

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