Ergonomics has significantly contributed to the improvement of human work conditions. In the Brazilian forest sector this contribution has been relatively modest mainly due to unawareness about ergonomic benefits and general lack of research. This study analyzed ergonomic factors in timber cutting operations using chainsaws, as a contribution to improving forest workers' health, well-being, safety, comfort and productivity. Specific objectives were: a) to carry out a timber cutting work study; b) to identify the chainsaw operator's profile, work conditions and opinions about ergonomic problems on the job; c) to determine the aerobic power and the energy expenditure of the chainsaw operator; and d) to determine the daily energy requirements of the chainsaw operator. The research was carried out in a large Brazilian pulp and paper company. The data were collected in timber harvesting operations in forest stands of Eucalyptus plantations divided in units of 50 hectares with 6.5 years of age and 3 x 2 m spacing. Timber cutting operations were carried out by two-men crews using a chainsaw that weighs approximately 8.0 kg.
A total of 45 chainsaw operators were studied. All operators were trained and had more than six months of work experience using chainsaws. The data were gathered by means of interviews, reviewing company records and measurements taken from October 1993 to April 1994. The main study conclusions are these:
The work study indicated that chainsaw operators carried out the following tasks: timber felling, limbing, bucking and bunching.
The workers had a daily eight hour shift and spent the greatest amount of their time bucking (37.4%), followed by felling (23.7%), resting (18.5%), limbing (12.4%), and bunching (8%).
The profile analysis indicated that the chainsaw operators were typically young, well trained, experienced, had few children or other economic dependents, encountered no drowsiness problems, were well fed and felt satisfied with their jobs.
The mean aerobic power of the population of chainsaw operators was 43.59 ml O2/kg/min or 14.8 kcal/min. Therefore, the daily (8 hours) energy expenditure limit for a chainsaw operator was 2352 kcal.
The operator mean energy expenditure in timber cutting operations (6.07 kcal/min or 2913.6 kcal/shift) was much higher than the workers' physical capacity. Overload was avoided by reorganizing the job; for each hour of work, the operator had a 15 minute rest period.
The timber cutting operation that consumed the most energy was bunching (8.58 kcal/min), followed by limbing (7.30 kcal/min), bucking (7.02 kcal/min) and felling (6.58 kcal/min). All operations were classified as heavy for the chainsaw operator except bunching, which was classified as very heavy.
The daily (24 hours) energy requirement for the chainsaw operator was approximately 3611 kcal.
Correspondence: Amauray Paulo de Souza, Department of Forest Engineering, Federal University of Viçosa (UFV), 36570-000 Viçosa, MG, Brazil