Saddle Seats for Tractor Drivers – A Conceptual Study

Abstract

Tractor drivers have quite often musculoskeletal problems because of bad sitting postures. It has been found that a good sitting posture is the one obtained when sitting on a horse with the hips in a muscle balanced rest position of 45°. A natural curvature of the spine is acquired as well as a perfectly balanced position in which the body obtains a good position of the centre of gravity. To improve the sitting posture of the driver of agricultural tractors, different types of saddle seats were adapted to fit in a tractor, and tested upon their comfort, work function and sitting posture. The saddle seats occupied less space in the horizontal plane compared to the conventional chair, and they were rotating freely during driving. Ten subjects employed as tractor drivers volunteered for the study. They harrowed and ploughed with three different saddle seats and one conventional tractor chair. Questions on experienced chair comfort and work function were asked. The drivers were video filmed from above and from the side in order to register their sitting posture. On a scale from 1 to 5 the conventional chair received a mean score of 3.6 and the saddle seats received mean score around 2. The difference is regarded to depend on differences in seat comfort. The saddle seats free rotation was mainly used during ploughing and reduced the spinal twisting 50%. The seat height adjusted by the tractor drivers was for the saddle seats 13 cm higher than for the conventional chair. This meant that the drivers received a sitting posture advantageous for the spine curvature. A future design of a tractor chair should have the possibility of varying raised sitting posture and free rotation. The seat should have a shape which gives a better seat comfort than any of the tested saddle seats.