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Three evaluations of task-surface Three evaluations of task-surface heights in elderly people’s homesheights in elderly people’s homes
Heli Kirvesoja et al. (1999)Applied Ergonomics
2009. 07. 08. Wed.Lee, Jee-hea
POSTECHHuman System Design Laboratory
ContentsContents
1. Introductiona. Aged-related changes in bodyb. Evaluation and aims of the study
2. Material and methodsa. Subjectsb. Mock-up simulatorc. Data collection and analysis
3. Resultsa. Score evaluation of task-surface heightsb. Scores on chairsc. Scores on kitchen facilitiesd. Subjective comparison of two different task-surface heightse. Human evaluations by the subjects and the expert vs. anthropometric
compatibility
4. Discussion and recommendationsa. Chairsb. Kitchen facilitiesc. General discussion
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1. Introduction1. Introduction
The number of elderly people ↑ Physiological capabilities ↓
Confine most of their activities to their homes (Meindle and Freivalds, 1992)
The time spent at home & the demands on home conditions ↑
For the ergonomic design of home facilities for the elderly Knowledge about human body size is important Information about functional capabilities, mobility, abilities as a function
of changes in biomechanical, physiological, psychological and mental characteristics is also needed (Kelly and Kroemer, 1990)
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1.1 Age-related changes in body1.1 Age-related changes in body
1. Stature Stature & Sitting height ↓ BUT, no change of the length of BSP (ex. Shoulder-to-elbow length,
elbow-to-middle-finger length) INSTEAD, decrease of functional reach (ex. Arm span)
2. Flexibility of joint of the body Decrease The disability of the elderly and the handicapped• Poor balance, lack of coordination, limited stamina, difficulty in handling and
fingering, in bending and kneeling, and inability to use the lower extremities (Sanders and McCormic, 1993)
3. The condition of musculoskeletal system Ability to maintain balance and stride length and steppage height
Decrease (Kivela et al., 1994) Muscle force Decrease (Rundgren, 1991) Muscle function Change (Berg, 1986) Musculoskeletal capacity Change ( Nygard et al., 1991)
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1.2 Evaluation and aims of the study1.2 Evaluation and aims of the studyEvaluation
The measurements to verify that a product will do what it is supposed to do
Should be done in actual operational situations Difficult to illustrate a work situation using an anthropometric model
• Standard anthropometric measure : static• Human actions : dynamic Full-scale mock-up
Home simulator• Small tasks (daily activities) according to oral instructions
Aims Part of a larger project which aims at improving the possibilities of the
elderly to move safely and to manage independently in their homes by gerontechnological means
Obtaining Static anthropometric measures To define how old people assess various different heights after a short-
term trial with task simulation using furniture or fixtures To compare the subjectively acceptable heights with the
recommendations given in the anthropometric literature
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2.1 Subjects2.1 Subjects
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Represent well the
corresponding Finnish elderly
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2.2 Mock-up simulator2.2 Mock-up simulator
Static mock-up simulator A room with furniture and fixtures whose heights could be adjusted
stepwise of with various task-surface heights Perform the task with every task-surface heights, which are from
1. The common heights of the environment the elderly lived in2. Structures that are commercially available
Three video camera record the whole body movements of the subjects
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Chairs Kitchen facilities
350450 550 450
w/ arm rest
The upper cupboard
The work surface heights
The kettle shelf
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2.3 Data collection and analysis2.3 Data collection and analysis
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1 2 3 4 5 6 7
Much too high
Too highSlightly too high
SuitableSlightly too low
Too lowMuch
too low
optimal chair seat height (OSH) = popliteal height + shoe height
AC (Δh) = actual seat height - OSH popliteal height
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3.1 Score evaluation of task-surface 3.1 Score evaluation of task-surface heightsheights
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The main statistics of subjects’ score (SS) and experts’ scores (ES)
(N=55)
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3.2 Scores on chairs3.2 Scores on chairs
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Condition
SS ES s.d.
350 Too low Lower High
450 (both)
Suitable Low
550Slightly too
highToo high high
The main statistics of SS and ES
The t-test between SS and ES
H0 : there is no difference between the scores
∴ there are difference between the scores except for 45cm with armrests
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3.3 Scores on kitchen facilities3.3 Scores on kitchen facilities
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The main statistics of SS and ES
The t-test between SS and ES
H0 : there is no difference between the scores∴ there are difference between the scores except with regard to the work surface height of 900 mm, at the α = 0.01 significance level
Kitchen facilitie
s
conditions
SS ES
Upper cupboard
LowSlightly too high
~ suitableSlightly too
high
High Slightly too high Too high
Work surface
80 cm SuitableSlightly too low
~ too low
90 cm SuitableSuitable ~ slightly too
high
Kettle shelf
16.5 cm Suitable Too low
26.5 cm SuitableSlightly too
high
Usually “too high”
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3.4 Subjective comparison of two 3.4 Subjective comparison of two different task-surface heightsdifferent task-surface heightsTo compare the difference between the subjects’ ratings of
two heights of the same furniture or fixtureWilcoxon’s matched-pairs signed-ranks test
H0 : there is no difference between the ratings of the two heights of furniture
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∴ All the differences of SS are statistically significant except 450mm and 450mm w/ armrest
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3.5 Human evaluations by the subjects 3.5 Human evaluations by the subjects and the expert vs. anthropometric and the expert vs. anthropometric compatibilitycompatibility
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EScomb
Regression EScomb = -0.19Δh + 4.55
Correlation r = - 0.89 (α = 0.000)
SScomb
Regression SScomb = -0.11Δh + 4.31
Correlation r = - 0.76 (α = 0.000)
Regression relation between score and Δh Correlation the degree to which the actual values agree with the predicted value
• EScomb is changed more by Δh than Sscomb. • The seat height is near the scores for “slightly too low” Seat height should be higher than OSH
• EScomb is changed more by Δh than Sscomb. • The seat height is near the scores for “slightly too low” Seat height should be higher than OSH
POSTECHHuman System Design Laboratory
Three evaluations of task-surface Three evaluations of task-surface heights in elderly people’s homesheights in elderly people’s homes
1. ES vs. SS (t-test)2. Each height ratings of SS (Wilcoxon’s test)
3. ES or SS vs. AC
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4.1 Chairs4.1 Chairs
The chair height of 400 mm is good Similar to 450mm in the present study
Elderly do not like higher chairs Even though being easier to get up from
The armrests did not affect the suitability scores If they have to sit for a long time on a chair, they prefer to have armrests Do not need armrests as a help for getting up from the chair
Positive relationship between patellar height and stature stature can be used as a reasonable aid to estimate
popliteal height when choosing chair seat height
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4.2 Kitchen facilities4.2 Kitchen facilities
Upper cupboard 1600 mm
Work surface 900 mm Elbow height 850mm Similar to 850mm in the present study
The lowest kettle shelf 300 mm Similar to 265mm in the present study
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4.3 General discussion4.3 General discussion
The Finnish elderly’s main anthropometric measuresMethods are useful and practicable for studying task-
surface heightsStature alone is not an adequate basis for designing task-
surface heights The elbow height, popliteal height, etc. should be measured 5th and 95th percentiles of measures other than mean and s.d. are needed
Classifications made at five-year intervals would be more suitable
Investigation of the static and dynamic anthropometry is necessary
The score of 4.3 is near “suitable” from regression
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Recommendations
1.Every aged person chooses for him/herself a proper fixed-height level
2.Adjustable height
Design for all
More applicable to cognitive characteristics than the basic
human measures
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