Results of investigation into the physical exertion of the log skidding workers: tractor driver, winch operator and choker are presented. The investigation consisted of laboratory and field measurements and included measurements of the heart rate and assessment of the work effect, the work time structure, and the worker's physical exertion and energy consumption. According to the average rate during daily work, the physical exertion of the tractor driver and winch operator was classified as low exertion (75-95 min-1), whereas that of the choker was established as medium exertion (96-115 min-1). Energy consumption was calculated for the daily working time of 262 minutes, according to field measurements and for normal eight-hour work. According to field measurement values the tractor driver's and winch operator's work was categorized as light work (1.23-2.51 MJ) and that of the choker as heavy work (2.52-6.30 MJ). According to the values for eight-hour work, the tractor driver's and the winch operator's jobs were classified as heavy work (2.52-6.30 MJ/8 h) and the choker's job as the heaviest (6.31-10.47 MJ/8 h).