During the 20th century, 20-25% of the occupational injuries causing lost work time were due to poor manual handling (Nelson and English, 2008).
In the early 1960’s, Swedish orthopaedic surgeon Alf Namchemson pioneered in vivo research of intra-discal pressure and found that flexed spines under load caused a doubling and more of those pressures. Combined with research showing forward creep with lumbar flexion, it was concluded that forward flexion of the spine under load was the primary cause of lifting back injuries and so “lifting with the knees and keeping the back straight” became the manual handling mantra.
To educate workers on the ‘safe’ lifting technique the Lifting Man plastic model was produced. The figure can raise a weight from either of two clearly marked positions. If the ‘correct’ position (load close, bent knees) is used the spine is not distorted. The ‘incorrect’ posture (distant load, bent back) causes demonstrable distortion to the spine, from which it was to be concluded that spine was under strain and likely to be damaged.
Physiotherapists were active participants in the training of manual handling techniques and the Lifting Man model became a vital tool in their training programs.
Recent research has identified weaknesses in the connection between loaded spinal flexion and back pain. Consequently, the Lifting Man model has fallen somewhat out of favour.
Description provided by Glenn Ruscoe of Australia
References:
Nachemson A and Morris JM. 1964. In vivo measurements of intradiscal pressure. The Jounal of Bone & Joint Surgery, 46(5), 1077-1092.
Nelson GS and English JT. 2008. Manual Lifting: Historical Sources of Current Standards regarding acceptable weights of lift. Nelson & Associates. Sourced online at http://www.hazardcontrol.com/factsheets/pdfs/historical-sources-of-current-manual-lifting-standards.pdf on 7 October 2021.
