During our thesis we measure physiological changes of our trainees, their stress levels, performance, and the number of mistakes, that they made during a series of 10. measurements, where they simulated the work of operator of the harvestor. This series of measurements was made on a simulator of harvester Komatsu. We used system BiofeedBack x-pert 2000 to measure physiological changes and Meister questionnaire to gain information about the stress levels our trainees felt. We tried to find out if there will be changes throughout the series of measurements. And also between the work phase and two rest phases. Out of all measured values of physiological changes, was for us the most interesting the heart rate. As we expected heart rate was in general higher during the work phase. Comparison of work phase hearth rate and rest phase heart rate showed us that work phase heart rate tended to increase throughout the series of measurements, while the rest phase heart rate tended to stay at a more constant level. Stress load negatively affecting our trainees ware caused by overload, hurry, nervousness, surfeit. Performance evaluation showed us that during the series of measurements, efficiency of trainees was increasing and they tended to do less mistakes.