A swivelling seat to improve tractor drivers' posture

Most agricultural equipment works behind the tractor, requiring the driver to spend a large proportion of his time looking backwards and adopting a poor posture. An evaluation was made of a mechanism that allowed a tractor seat to swivel up to 20 degrees from the normal forward facing position. Electromyographic techniques were used to monitor muscle activity during static laboratory experiments and angles of body twist were measured from photographic records in a separate study. The results showed a decrease in muscle activity in the shoulder and neck regions when the seat was swivelled up to 20 degrees. Measured angles of body twist showed that the potential benefit of swivelling the seat was not fully utilised by subjects although the mean twist between the shoulders and hips reduced significantly with increasing swivel angle. A subjective evaluation at three farms over a period of 6-12 months confirmed that a swivelling seat was of benefit to the driver, particularly for tasks requiring mainly rearward visual monitoring.