repetitive movements of upper limbs in vegetable grafting: the risk of musculoskeletal disorders for...
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Repetitive Movements of Upper Limbs in Vegetable Grafting: the Risk of Musculoskeletal Disorders for Workers
Colantoni A., Cecchini M., Monarca D., Menghini G., Bunescu M., Bedini R., Marucci A.
From Effective to Intelligent Agriculture and ForestryXXXV CIOSTA Conference 2013
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Introduction The herbaceous grafting in horticulture is a practice widely
spread and it permits to join the quality and productivity characteristics with those of resistance to pathology transmitted by the soil, much more quickly as regards the time necessary for genetic improvement.
There are different methods of grafting (crown, cleft, whip grafting, etc.): anyhow grafting must be effected by skilled workers and is effected with a grafting knife.
The workers who effect grafting for more than six hours a day, may damage their health owing to repeated movements.
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Introduction
Eurostat, 2009INAIL, 2012
Materials and Methods OCcupational Repetitive Actions (OCRA) index
ISO 11228-3:2009 Ergonomics - Manual handling - Part 3: Handling of low loads at high frequency.
EN 1005-5:2007 Safety of machinery - Human physical performance - Part 5: Risk assessment for repetitive handling at high frequency.
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The model uses an “exposure index” (OCRA index), which is defined by the ratio:
ATA = overall number of actual technical actions needed in the workers’ shift
RTA = overall number of reference technical actions (i.e., the total number of actions recommended so as not to expose the workers to risks) in the shift.
The OCRA index
RTA
ATAOCRAindex
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RTA is obtained from the following equation:
CF = “constant of frequency” of technical actions per minute recommended in good conditions (= 30)
FoM = multiplicative coefficient for forcePoM = multiplicative coefficient for postureAdM = multiplicative coefficient for additional factorsReM = multiplicative coefficient for repetitiveness D = net duration of the repetitive task in minutesRcM = multiplicative coefficient for the “lack of recovery period”DuM = multiplicative coefficient for the overall duration of
repetitive tasks during a shift.
The OCRA index: definition of RTA
)(Re DuMRcMDMAdMPoMFoMCFRTA
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The OCRA index: definition of FoM
Score Description Score Description
0 Completely absent 5 Strong0.5 Extremely light 6 Strong (+)1 Very light 7 Very strong2 Light 8 Very strong (+)3 Moderate (modest) 9 Very strong (++)4 Modest (+) 10 Maximum
Average perceived exertion
≤0.5 1 1.5 2 2.5 3 3.5 4 4.5 ≥5
Force Factor (FoM) 1 0.85 0.75 0.65 0.55 0.45 0.35 0.2 0.1 0.01
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The OCRA index: definition of PoM Re
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The OCRA index: definition of PoM
Awkward Posture Portion of the Cycle Time
1% to 24%(<1/3)
25% to 50%(1/3)
51% to 80%(2/3)
>80%(3/3)
Elbow supination (>60°)Wrist extension (>45°) or flexion (>45°)Hand pinch or hook grip or palmar grip
(wide span)
1 0.7 0.6 0.5
Elbow pronation (> 60°) or flexion/extension (>60°)
Wrist radio-ulnar deviation (>20°)Hand power grip with narrow span (<2 cm)
1 1 0.7 0.6
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The OCRA index: definition of AdM
The main additional factors include the use of vibrating tools, gestures implying countershock (such ashammering), requirement for absolute accuracy, localized compression of anatomical structures, exposure to cold surfaces and environments, the use of gloves interfering with handling ability and high pace completely determined by the machinery.
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Presence of additional factors AdM
Less than 25% of the cycle 1
1/3 (25% to 50%) of the cycle 0.95
2/3 (51% to 80%) of the cycle 0.90
3/3 (>80%) of the cycle 0.80
The OCRA index: definition of ReM Re
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ReM
the task requires the performance of the same technical actions of the upper limbs for at least 50% of the cycle time
0.7
the cycle time is shorter than 15 seconds 0.7
other 1
The OCRA index: definition of RcM
Work/Recovery Ratio Recovery Risk
From 5/1 to 6/1 Adequate 0
From 7/1 to 11/1 Not satisfactory 0.5
>11/1 Not sufficient 1
Number of hours without adequate recovery periods
0 1 2 3 4 5 6 7 8
Multiplicative factor (RcM)
1 0.90 0.80 0.70 0.60 0.45 0.25 0.10 0
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The OCRA index: definition of DuM
Total time devoted to repetitive tasks during shift (min)
≤180 181 to 240 240 to 480 >480
Duration multiplier (DuM)
2 1.5 1 0.5
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Classification of OCRA Index results for evaluation purposes
RTA
ATAOCRAindex
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The case study Re
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Study of the workshift
Job Description Duration(min)
Type of Job(repetitive/not repetitive)
1 Manual grafting with knife 225 Repetitive
Recovery Time or Not
1st break Lunch break 105 Recovery time
2nd break Breaks due to cleaning, supply 30 Recovery time
Total minutes of actual work and breaks 360
FCT
NTCFF
60 (actions/min) DFFATA (actions/shift)
Results Re
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To graft a vegetable, 15 actions with the right limb and 6 with the left limb are performed in 20 seconds. The workers make movements that involve the same portions of the limb for almost all the time.
takes the plant (1)places it on the table (2)removes the right basal leaf (3)removes the left basal leaf (4)puts removed leaves in the container (5)takes the knife (6)cut the plant at the base on the right side (7)cut the plant at the base on the left side (8)rests the knife on the table (9)takes the rootstock (10)insert the plant into the rootstock (11)takes the clip (12)inserts the clip at the base junction between the rootstock and the plant (13)insert the grafted plant into the container (14)moves the arm to the new plant (15)
RIGHTLEFT
stretches out towards the plant (1)takes hold of it (2)picks it up (3)pulls back the arm (4)bends the wrist downwards (5)cuts the plant into two different parts (6)
Results Re
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LEFT RIGHT
4520
1560 rFF18
20
660 lFF actions/min actions/min
ATAr = 45 actions/min 225 min/shift
= 10125 actions/shiftATAl = 18 actions/min 225 min/shift =
4050 actions/shift
Borg 0.5 FoM 1.00 Borg 1 FoM 0.85
PoM 0.33 PoM 0.33
Presence in the cycle time
1-3
AdM 0.95 Presence in the cycle time
2-3
AdM 0.90
Force
Posture
Complementary factors
Force
Posture
Complementary factors
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LEFT RIGHT
Time devoted to repetitive tasks during shift
181
240 min
DuM 1.50
working time/recovery periods
7/1
11/1
RcM 0.80Recovery periods
DurationTime devoted to repetitive tasks during shift
181
240 min
DuM 1.50
working time/recovery periods
7/1
11/1
RcM 0.80
Duration
Recovery periods
Movements that involve the same portions of the limb for almost all the time
ReM 0.70Repetitiveness
Movements that involve the same portions of the limb for almost all the time
ReM 0.70Repetitiveness
Results Re
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LEFT RIGHT
1.71431/10125 rOCRAindex3.21778/4050 lOCRAindex
1778)5.18.0225(7.0
95.033.0130
lRTA
1431)5.180.0225(7.0
90.033.085.030
rRTA
2.3 7.1
Conclusion The results of this
research show a high risk for the right limb which effects the cutting up on the small vegetables to be grafted and a low risk for the left limb.
The factors which have contributed to reach such results are to be attributed to the continuous pinch of the knife, to the great number of movements and to the lack of recovering time.
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Grafting operations force workers to maintain an elbow pronation greater than 60°, with respect to a resting position, for 80% of the cycle time.
Repetition is particularly risky due to very short cycles that are repeated for more than 50% of the working time.
It does not seem possible to eliminate the risk of biomechanical overload in this job, but at least it could be reduced.
Conclusion cont’d Re
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Conclusion cont’d Despite these limitations, the findings from our study
demonstrate that alternative patterns of rest breaks, including brief rest breaks early in the work shift, may reduce workers’ musculoskeletal discomfort and fatigue over the course of the day with modest impact on production.
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Therefore, it would be a good idea to reorganize such work by including recovery times right from the earliest working hours. Although we tested the rest break intervention in agriculture, similar interventions are likely to benefit workers in other strenuous jobs such as construction and manufacturing
Conclusion cont’d
Repetitive tasks can be an important factor in these processes, but not the only cause (Barr and Barbe, 2002). Some studies show that pathology may develop as a result of the summation of several constitutional and environmental factors, some of which are not related to work. In addition to biomechanical constraints, psychosocial and personal factors play a role (Leclerc et al., 2001).
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Conclusion cont’d
In order to reduce the incidence of upper limb work-related musculoskeletal disorders (UL-WMSDs) health surveillance must start in preemployeed phase.
A good anamnesis and a clinical examination performed with attention may identify hyper-susceptible persons. It's recommended to avoid exposure of these persons to repetitive actions with high risk.
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Conclusion cont’d After employment must carry out an information about
risks and specific training of workers. The aim is to learn the right movements and maintaining proper posture during work shift.
When the risk intensity is higher health surveillance should focus on the recognition of early symptoms and signs of musculoskeletal disturbances.
Workers showing early disturbances as a result of repetitive movements must start medical rehabilitation. Two stages (according to the clinical aspect): a first acute-subacute stage which is potentially reversible and a chronic stage which is non-reversible.
The health surveillance programme should be adopted to the workplace.
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Thanks for your attention…R
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Mo
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Gra
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Risk o
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