REPETITIVE MOTION AND POSTURAL ANALYSIS OF MACHINE OPERATORS IN MECHANIZED WOOD HARVESTING OPERATIONS

Paini, Anderson de Costa; Lopes, Eduardo da Silva; Souza, Amaury Paulo de; Oliveira, Felipe Martins de; Rodrigues, Carla Krulikowski

doi:10.1590/01047760201925022617

ABSTRACT

The objective of this study was to evaluate operators’ posture and repetitive motions in the mechanized wood harvesting operations, aiming comfort, safety, and health of forest operators. The study was carried out in the clearcutting of pine stands located in Paraná State, Brazil. Data were obtained in tree cutting operations with feller buncher and wood processing with harvesters, in which three operators in each machine were filmed during their workday. The typical postures were evaluated by Rapid Whole-Body Assessment (REBA) and Rapid Upper-Limb Assessment (RULA) methods, while repetitive motions were evaluated by Latko, Silverstein and Strain Index (SI) methods. The results showed the feller buncher operators remained long period seated in static position, with fists turning outside the neutral line and without pauses for recovery, although REBA and RULA methods had identified low postural risk. In wood processing operation, the spinal column and neck were the most affected body parts, presenting medium postural risk and the need for investigations and quickly changes by REBA and RULA methods, respectively. Besides that, wood harvesting operations with feller buncher and harvester were classified as high repeatability, showing more than 30 thousand repetitive motions in a workday, indicating high risk of Repetitive Strain Injuries (RSIs) and Musculoskeletal Disorders (MSDs) in the operators. Therefore, it is concluded the ergonomic measures are necessary to improve operators’ comfort and health.

Keywords:
Ergonomics; Forestry; Health; Mechanized harvesting

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Variables	Feller buncher	Harvester
Age (years)	47.3 ± 10	42.0 ± 8.0
Height (m)	1.75 ± 0.07	1.72 ± 0.08
Body mass (kg)	90.1 ± 9.9	84.0 ± 7.0
Experience time as machine operator (years)	20.3 ± 5.2	8 ± 1.4
Experience time in a current machine (years)	7.3 ± 3.1	3.3 ± 1.2

Score	Action level	Risk	Action (providence)
REBA (Rapid Entire Body Assessment)
1	0	Insignificant	Acceptable posture; actions are not required
2 or 3	1	Low	Actions may be required
4 to 7	2	Medium	Actions are required
8 to 10	3	High	Actions are quickly required
11 to 15	4	Very high	Actions are immediately required
RULA (Rapid Upper-Limb Assessment)
1 or 2	1	*	Acceptable posture if not maintained or repeated for long period.
3 or 4	2	*	Investigations and possible work changes are required.
5 or 6	3	*	Investigations are required, as well as possible quickly work changes.
7 or more	4	*	Investigations are required, as well as possible immediately work changes.

Typical posture	Percentage of time in the posture	Assessment method
Typical posture	Percentage of time in the posture	REBA	RULA
Cutting with feller buncher
SC/MB	100	S = 3 A = 1 R = low D = there may be a need for action	S = 3 A = 2 D = further investigation and possible changes needed.
Processing with harvester
SE1/PR1	79	S = 4 A = 2 R = medium D = there is a need for action.	S = 3 A = 2 D = further investigation and possible changes needed.
SE2/PR2	21	S = 6 A = 2 R = medium D = there is a need for action.	S = 5 A = 3 D = necessary investigations and changes quickly.

Operation	Latko et al. (1997LATKO, W. A.; ARMSTRONG, T. J.; FOULKE, J. A.; HERRIN, G. D.; RABONRN, R. A.; ULIN, S. S. Development and evaluation of an observational method for assessing repetition in hand tasks. American Industrial Hygiene Association Journal, v.58, n.4, p. 278-285, 1997.) scale	Silverstein criterion (1985)	StrainIndex method (Moore and Garg, 1995MOORE, S.; GARG, A. The strain index: a proposed method to analyze jobs for risk of distal upper extremity disorders. American Industrial Hygiene Association Journal , v.56, n.5, p.443-458, 1995.)
Cutting with feller buncher	S = 8 F = constant rapid movement or continuous effort, pauses not frequent A = high repeatability	F = average cycle time less than 30 seconds and same element covering more than 50% of the cycle A = there is repeatability	S = 20.3 F = above 7 points A = high risk of RSIs/MSDs
On-site processing with harvester	S = 8 F = constant rapid movement or continuous effort, pauses not frequent A = high repeatability	F = more than 4 repetitive motions by minute and same element covering more than 50% of the cycle A = there is repeatability	S = 20.3 F = above 7 points A = high risk of RSIs/MSDs

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REPETITIVE MOTION AND POSTURAL ANALYSIS OF MACHINE OPERATORS IN MECHANIZED WOOD HARVESTING OPERATIONS

ABSTRACT