"The present cross-sectional study was performed to analyze potential risk factors for upper extremity disorders in two groups of forest machine operators driving harvesting vehicles and performing equal tasks in France (n=18) and Norway (n=19). This comparative design implied similar work tasks, but potentially different external work demands. Previous studies have suggested higher levels of neck and shoulder complaints among Norwegian operators compared to those of the French. This may be related to different external work demands and/or individual motor performance.Surface electromyography (EMG) of the right upper trapezius (RUT) and extensor digitorum (RED) muscles were measured continuously during 1 working day (7.5–8 h per operator) and video of body postures was recorded inside the cabin (1 h per operator). A questionnaire on external work demand factors and psychosocial stressors was used together with the collection of symptom data. A physical examination was performed on all workers. Borg's CR-10 scale of intensity of discomfort/pain was rated four times throughout the test day.The French operators reported less complaint (p<0.01) in the right neck compared to their Norwegian colleagues. Furthermore, the French had on average two to three times longer lunch breaks during 5 work days, less continuous hand intensive use of the control lever with more frequent short breaks during the test day compared to the Norwegian operators. However, the average static load level on the RUT muscle for the whole working day was significantly higher among the French (0.7% EMGmax) in comparison with the Norwegian operators (0.3% EMGmax). No difference was found in number of periods with sustained low-level muscle activity neither in the RUT nor the RED muscle.In conclusion, our results support that the higher prevalence of discomfort/pain among the Norwegian forest machine operators may be related to organizational factors."

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