During nine months, nineteen hairdressers every second/third month switched the use between a blow dryer with traditional design and one with a new design. The new blow dryer had the possibility to change between two opposite directed air flows. Every second/third month arm inclination angle and upper trapezius muscle activity were measured a whole workday, and during blow-drying in the laboratory. Pronounced upper arm elevation was reduced with the new blow dryer. The muscle activity of the upper trapezius was only reduced in the laboratory, and daily pain reports were not significantly influenced at all. The subjective rating of time use, functionality and heaviness was less favourable for the new blow dryer, with only three out of nineteen preferring the new dryer at the end of the study period. However, the design of the new dryer demanded a change of work technique that might have been conceived as problematic by the experienced hairdressers.