This study examined the physical strain experienced by chainsaw operator and the applicability of heart rate indices for measuring physical strain in forest felling operations in north eastern region of Turkey. The heart rate of ten chainsaw operators were recorded continuously throughout the working day and applied to heart rate indices. The average working heart rate was 122.8 beats/minute (bt. min(-1)), while the pre-work resting heart was 70.5 bt. min(-1). The average physical workload (%HRR) rate range was 44.79, while the ratio of working heart rate to resting heart rate was 1.74. The average ratio of working heart rate to 50% level was 0.97. The workers had a mean estimated maximum aerobic capacity (Vo(2 max)) of 43.34 milliliters per kilogram and minute (ml kg(-1) min(-1)). All physiological measures placed the task of chainsaw operations in the heavy workload categories. Average hourly production decreased from 8.5 m(3) in the morning to 7 m(3) in the afternoon. The cutting-falling phase accounted for 30% of the hazards, with the remaining 70% occurring during branch cleaning. This study also shows that heart rate indices can be used as an effective means of determining the physiological strain of subjects in applied field situations. The workers will achieve optimum physical and mental performance if they are provided by an adequate fluid and food throughout the day.