In-season physiological and biochemical status of reforestation workers

Tree-planting demands sustained high work-output and is associated with high injury rates but has not been characterized previously. Data were collected from 10 male planters after 19 +/- 5 (T1) and 37 +/- 5 days (T2) of planting. One severe infection and one knee strain injury were noted. Loads carried were 32% +/- 5% body mass and heart rates were between 60% to 75% of maximum for 57% +/- 26% of the planting shift. A loss of 1.7% +/- 1.5% body mass occurred, although intake exceeded 5000 kcal/day. From 8% (T1) to 27% (T2) of postprandial blood glucose samples were found to be < 3.3 mmol/L. Further evidence of the cumulative stress was seen in increased levels of resting cortisol (428 +/- 163 to 741 +/- 103 mmol/L), norepinephrine (2.09 +/- 1.34 to 3.09 +/- 1.05 mmol/L), and creatine kinase (184 +/- 82 to 397 +/- 174 U/L) at T2. The postactivity neutrophilia and lymphophilia (absolute count, CD4+ and CD8+) observed at T1 were blunted at T2. The implications of mild hypoglycemia, including possible effects on cognitive and motor function, warrant further study.