Work accidents, employee absenteeism and turnover
in restaurants may be related to human factors
issues such as Cumulative Trauma Disorders (CTDs).
These injuries often fall under work related musculoskeletal
disorders. Common CTDs occur in areas of
back, neck, shoulders, hands, and other joints. These
disorders can be very painful and lower work efficiency
and productivity. Symptoms can develop
without the person realizing it. The average rate of
CTDs in high-risk occupations can be as high as 15-
20%, and of reported CTD cases, 48% of the victims
are not well enough to return to work [6]. CTDs, as
opposed to sudden accidents due to lack of safety,
actually can be harder to prevent because employers
and even employees themselves may not think about
the risk. High physical workload can cause body
stress and can influence employees to take careless
shortcuts. It can cause sudden accident/injury and
lead to fatigue and lower job satisfaction. Cognitive
workload refers to “the degree or percentage of the
operator’s information processing capacity which is
expended in meeting system demands” [2]. High
cognitive workload can lower the quality of physical
and mental health.
The nine participants were servers at a country
club dining room. The task areas analyzed included
table management (e.g. taking customers’ orders,
clearing/setting tables), carrying/lifting tubs filled
with eating utensils, and polishing silverware/glassware
2.2 Ergonomic Assessments
These included an ergonomic checklist, CTD risk
formula (all 3 tasks), self-report cognitive workload
scale (table management task) and self-report physical
exertion questionnaire (polishing task).
2.2.1 CTD risk formula [7]
There are three factors: Task (weight = .637), Personal
(weight = .258), and Organizational (weight
= .105). These risk factors themselves are multidimensional.
Each factor was assessed by the authors
on a scale from 0 (no risk) to 1 (high risk). An example
of task risk is preparing dough for a pizza, which
was calculated to be 0.711 [5]. Task risk factors
include ratings on awkward joint posture, repetition,
hand tool use, force, task duration, and vibration.
Personal risk factors include ratings on previous
CTDs, hobbies and habits, diabetes, thyroid problems,
age, and arthritis. Organizational risk factors include
ratings on equipment, production rate/layout,
ergonomics program, peer influence, training, CTD
level, and CTD awareness.
2.2.2 Cognitive workload scale (Likert 1-7 rating for
each item)[1]
The following include the items and the scale for
each item: Overall workload (very low-very high),
task difficulty (very easy-very hard), time pressure
(none-very rushed), actual performance (lousy-great),
comfort level (very low-very high), mental/sensory
effort (very low-very high), skill required (none-very
much), fatigue (worn out-wide awake), stress level
(completely relaxed-extremely tense).
2.2.3 Physical workload scale [3]
This scale ranged from 1 (minimal exertion) to 10
(extreme exertion). Participants rated their physical
exertion every 5 minutes for 50 minutes total. This
scale has been found to be highly correlated with
more objective measures of physical workload such
as heart rate [4].
3. Results
3.1 Results for carrying/lifting task
The task risk factors for carrying/lifting was
0.5753 (moderate to high moderate risk). The organizational
risk factors was lower at 0.4838.
Figure 1 depicts the personal risk factors across
all participants. The overall CTD risk across task,
personal, and organizational risk factors for carrying/lifting
was an average of 0.51, equating to moderate
risk. The range for overall CTD risk across all
participants was 0.44 - 0.60.
Fig 1: Personal CTD risk for each participant
3.2 Results for table management task
Overall cognitive workload (item 1) was rated on
average to be 4.67. Skill required (item 7) and stress
level (item 9) were both rated at 4.33. Time pressure
(item 3) was 4.44. Highest workload rating across all
items was with mental/sensory effort (item 6), at 5.11.
All items were rated out of 7 maximum. For actual
performance (item 4) and comfort level (item 5), the
lower the rating, the higher the workload. Task CTD
risk was 0.4248.
Fig 2: Average cognitive workload ratings per item and per participant
3.3 Results for polishing task
The task CTD risk was 0.7025 (moderately high
risk). The average overall CTD risk was 0.59, with a
range of 0.52 - 0.68. The physical workload ratings
yielded only a mild to moderate amount, with an average
rating of 3.65 (SD = 0.92). Across time on average
these ratings increased steadily from 5 – 20
minutes into the task. It was fairly steady from 20 to
35 minutes, rose significantly from 35 – 45 minutes,
and then decreased slightly from 45 – 50 minutes.
Fig 3: Average rating of physical exertion across time
4. Recommendations
4.1 Carrying/lifting task
The easiest way to prevent injury is to lower the
weight of the items. It would also be beneficial to
have the load at a higher level. Ideally the servers
would not place trays on the floor, and maybe could
even have a mechanical lift to lift the tray. Another
idea is to have a grip on the tray for better handling.
Better designs for carts should also be considered,
such as installing rollers on shelves and having improved
handling.
4.2 Table management task
One suggestion to reduce cognitive workload is
to have a touch-screen monitor at the table to order
from and a small device to swipe a credit/debit card.
What could also help reduce physical strain and
chances for injury are mechanical lift for tables that
are low, similar to what is on an office chair. Or one
could have all tables raised on a platform base. If this
is not possible, maybe servers could use a reaching
device to pick up objects across a table and to clean.
Another possibility is to include folding bench seats
at booths so employees can fit in to clean the table. A
more extreme change to reduce physical workload is
to limit walking distance by changing the structure of
the restaurant to have a central kitchen.
4.3 Polishing task
To reduce the risk of injury, higher work surfaces
could be built to rest arms on. A chair might be helpful
to reduce leg strain from standing the entire time
and reduce torso bending. Moreover a chair could
include arm rests. If possible, to reduce repetitive
strain, use some type of automated hand tool to help
with polishing that would be very gentile on glassware.
References
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research (PETER): Critical tracking test, Perceptual
and Motor Skills 58(2) (1984), 567-573.
[2] F. T. Eggemeier and R. D. O`Donnell, R. D, A conceptual
framework for development of a workload assessment methodology.
In Text of the Remarks made at the American Psychological
Association Annual Meeting. Washington D. C.:
American Psychological Association, 1982.
[3] G. Borg, A category scale with ratio properties for intermodal
and interindividual comparisons, in: Psychophysical judgment
and the process of perception, H. G. Geissler and P. Petzold,
eds., VEB Deutscher Verlag der Wissenschaften, Berlin, 1982.
[4] K. H. E. Kroemer, H. B. Kroemer and K. E. Kroemer-Elbert,
Ergonomics: How to Design for Ease and Efficiency, Prentice
Hall, Upper Saddle River, NJ, 1994.
[5] M. Gentzler, M. Kline, A. Palmer and M. Terrone. Assessment
of CTD risk for three different tasks: Constructing and repairing
multi-layer insulation (MLI) blankets, preparing the dough
for a pizza, and operating the Becton-Dickinson Facsaria Flow
Cytometer, proceedings of the international conference on industry,
engineering, and management systems 13 (2007) 315-
323.
[6] P. McCauley-Bell, In-class powerpoint presentation on cumulative
trauma disorders, 2006.
[7] P. M. Bell and L. Crumpton, Fuzzy linguistic model for the
prediction of carpal tunnel syndrome risks in an occupational
environment, IBM Journal of Research and Development 44
(2000), 759-769.
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