Postural changes due to fatigue

One of the most critical risk factors contributing to injury of the low back is posture, specifically of the torso. Though considerable time and expense is directed towards training workers to use postures which minimize biomechanical stress, there is a growing body of evidence suggesting that this training may not be effective over shifts of extended duration. This may be due to a combination of fatigue and loss of concentration. Ten healthy subjects who had been previously trained in proper lifting technique lifted a load of 120% of their maximum acceptable weight of lift (MAWL) at a frequency of three lifts per minute for two hours or until they were no longer able to continue due to fatigue, whichever came first. Subjectsʹ self-selected postures were quantified in terms of maximum torso flexion and the distance between the hands and the L4/L5 spinal disc. Changes in posture were evaluated as a function of time, heart rate and perception of fatigue.