ERGONOMICS OF TREE PLANTING WORK AMONG BRITISH COLUMBIA FOREST WORKERS

Little objective data exist characterizing the ergonomic demand of tree planting work although a substantial number of workers are seasonally employed in the industry each year in British Columbia. The purpose of this study therefore was to determine the ergonomic factors of the job and analyse the variation in physical, physiological, biochemical, and health indices of a group of tree planters who were periodically assessed in a field camp throughout a planting contract period. Sixteen British Columbia reforestation workers were studied during their employment on a tree planting contract throughout a total period of 75 days. Their work was organizes in shifts of about five days on and one or two days rest. Each worker was studied on the first day of each work shift and data were collected on each in the morning upon their awakening and again in the evening upon their return home from work. A blood sample was taken from a subject on each of these occasions. A simple health questionnaire was completed once per day. Throughout the day a subject's heart rate was continuously monitored and their work habit videotaped. Blood samples were later analyzed for cortisol, elevated serum muscle enzyme activity (ESEA); creatine kinase (CK), Lactate Dehydrogenase (LDH) and asparate serum transferase (AST), and blood hematology parameters (BH), hematocrit (Hct), red blood cell (RBC), and hemoglobin (Hgb). Camp organization, worker health, and work time distribution was analysed from the questionnaire and videotape records. The mean working heart rate of the tree planters studied was 117 barnin-1 (range 100-139). This rate was sustained throughout an 8.0 hour day and represented 39.2% of the age predicted maximum above a resting baseline heart rate (AHRratio). Serum cortisol concentration showed a significant variation among sample day means for only the pre-work measure (ANOVA, p10.05) and indicated a slight decreasing trend during the planting period. The remaining blood data were analyzed for each sample day only for a subset of planters (n=10) of the original 16, who survived throughout the whole planting period. Preand post-work ESEA of these workers were both significantly higher on each sampling occasion throughout planting period compared with a pre-season resting control group (n=9, p10.01). The difference between the preand post-work serum concentration of CK and AST decreased in most workers during successive weeks of planting as they adapted to the work routine. LDH continued to rise however and remained significantly elevated on the last sample day of the period (day 32) compared with the first day. A decreasing trend in BH parameters was observed during the period, which did not however become significant. Pooled blood data from all subjects for the whole period showed a highly significant difference (p10.01) between preand post-work samples for all BH parameters as well as ESEA (BH parameters decreased and ESEA increased). These data suggest that the the work/rest schedule practiced in the camp under study was not optimal, producing incipient debilitating changes that may have compromised a worker's well-being and productivity.