Ergonomic aspects on snowmobile driving.

From self-reported health surveys in Finland, Sweden and Norway we know that the reindeer herders have work related disorders. It is very likely that disorders such as lumbar back pain, neck and arm pain, knee pain and white finger syndrome are related to snowmobile driving. Our hypothesis was that driving postures, vibrations, impact from the driving surface and handling are the main reasons for the health problems, and that snowmobiles are not designed according to ergonomic principles. Our work started in the winter of 1993. We studied the general literature available on ergonomic postures, measurements of vibrations and body impact and we set out to explain the problems associated with driving and handling snowmobiles from a physiological, ergonomic and biomechanical point of view. At this point we identified some ergonomic requirements and requirements for the springing system of snowmobiles. We made static tests in which we watched the sitting position of the driver and tested the springing suspension. This was followed by a driving test and field observations of reindeer herders in 1994. The total load when driving comprises the load of the posture added with the load from vibrations and impact from the ground (3-10 G). The driving positions probably giving the most health problems are sitting with bent back, hyperlordotic neck, too high upper arms, more or less straight elbows and flexed and ulnar deviated wrist positions. The design of the snowmobile should enable the driver to sit with straight back, the hip joints at less than 90 degrees, knee joints at about 45 degrees, shoulder joints at 45 degrees, elbow joints around 60-70 degrees and the hand in a neutral position. The seat should be higher at the back and narrowed between knees. The height of the seat should be about 50 cm. The height of the steering-bar should be around 80 cm. The distance between the body of the driver and the steering-bar should be about 50 cm. Only one snowmobile was close to our requirements with a seat height of 48 cm and steering-bar height of 75 cm. The seat height varied with 10 cm, and the height of the steering-bar from 64 to 75 cm. The gas-bar should be placed on the thumbside so that it is possible to use the accelerator with the fingers.(ABSTRACT TRUNCATED AT 400 WORDS)