Assessment of workload from measurements of stature.

The height of the body in the erect position varies by about 1% during the course of the day. It decreases rapidly after getting up and, depending on the pattern of work and rest, continues to reduce during the day; then overnight, it recovers. These changes result from changes in the height of the intervertebral discs. With conventional methods of measuring stature, these changes would go unrecognised. Apparatus has therefore been developed, allowing measurement to an accuracy of at least 1 mm. Studies have been made of static loading, dynamic lifting, running, in different types of seating and in resting postures. In general, height losses are proportional to the magnitude of lumbosacral compression, to the perception of exertion during physical exercise and to the levels of postural discomfort. Gains in height in positions of rest are proportional to the ratings for relaxation and comfort. For the ergonomist, therefore, the method offers a reliable means of assessing the effects on the spine of both physical work and rest-pauses.