CARDIOVASCULAR AND MUSCULAR STRAIN DURING A TREE PLANTING SEASON AMONG BRITISH-COLUMBIA SILVICULTURE WORKERS

Cardiovascular and muscle strain were determined in 16 British Columbi a reforestation workers during a period of tree planting (75 days). Se rial data collected from each worker included pre- and post-work blood chemistry on the first day of the work shift; working heart rate (HR) , a PWC170 fitness test, and a daily diary of an individual's work-res t schedule. Repeated blood samples from each planter were analysed for the elevated serum enzyme activities (ESEA) of creatine kinase (CK), lactate dehydrogenase (LDH), and aspartate transaminase (AST), and for the blood haematology parameters (BH) of haematocrit (Hct), red blood cell count (RBC), and haemoglobin (Hgb). HR and BH were used as an in dex of cardiovascular strain and ESEA was used as an index for musculo skeletal strain. A group mean working heart rate of 116-5 +/- 9 b.min- 1 (range 100-0-139.1) was sustained throughout the period of an 8.0 ho ur day representing 39.2% of the DELTAHeart Rate ratio (ratio of eleva ted working Hr above resting to maximum HR). Grouped data were analyse d by sample day for a subset of planters (n = 10) participating in six sample dates during the first 32 days of planting. Pre- and post-work ESEA were significantly higher throughout the entire planting period when compared with a pre-season resting control group (n = 9, p less-t han-or-equal-to 0.0 1). The post-work rise in CK and AST from pre-work values decreased during successive weeks of work as some adaptation t o the work rate occurred. LDH continued to rise and was significantly elevated on day 32 compared with day 1. No significance was found in t he BH variables between sample dates, yet a decreasing trend was obser ved. However, pooled data from all subjects for all sample dates showe d a highly significant difference (p less-than-or-equal-to 0.01) betwe en pre- and post-work samples for both ESEA and BH. ESEA increased and BH decreased. These data present evidence that the work rate and rest time of a tree planter are not well ordered within the daily and seas onal working routine, and may compromise worker well-being in the silv iculture industry.