Does anyone know of a government guidance publication that attempts to
deter designers from designing checkout workstations for seated workers (or
any other seated workstations for workers who have to do lifting tasks for
that matter)? We used to have one or two in Australia but I seem unable to
find them now. Failing that is there one discourages drivers from performing
lifting tasks immediately after prolonged sitting?
According to my records the arguments for these recommendations are as
follows. The hazards of lifting during or after prolonged sitting have been
researched in Ergonomics at least as far back as the seventies; that era
featured some landmark papers that contended that tasks involving prolonged
sitting (sitting for a period of 4 hours or more) can lead to lower back pain
This is a particularly severe problem for drivers. Workers who spend more
than half there working life driving all three times more likely to suffer from
back trouble than the rest of the population (Troup, 1978). Alteration of
postures between sitting and standing appears to reduce the risk of back pain
and back injury (Magora, 1972); periodic alterations of seated postures are
also beneficial since the discs do not have a blood supply and intermittent
movement is necessary for their nutrition.
The “Eleven Commandments of Ergonomics” stated that work procedures
should be designed to ensure that the worker does not have to stand
continuously for more than 30 minutes or sit continuously for more than an
hour (Van Wely, 1970) wherever this is possible.
The topic of lifting during or after prolonged sitting has been researched with
even greater rigor in recent years. Canadian research in the field of sports
physiology has found that bench rest after a warm-up leads to an increase in
the stiffness of the lumbar spine prevents optimal performance and increases
the risk of back injury (Green et al, 2002).
Research shows that sustained static loading of lumbar visco-elastic tissues
can cause micro-damage to its collagen and this can cause muscle spasms
and results in inflammation (Solomonow et al, 2003). A mere 20 minutes of
static flexion results in creep of lumbar connective tissues that does not fully
recover over a 7-hour period.
Current evidence from the field of Manual Therapy suggests that prolonged
sitting increases the chance of injury because increased creep and the
resulting decrease in the effectiveness of the neuromuscular reflex
coordination (Preuss and Fung, 2005). It is now believed that prolonged sitting
may increase the risk of low back injury due to changes in the passive flexion
stiffness of the lumbar spine (Beach et al, 2005).
Professor Stuart McGill provided the following advice in the textbook on low
· The recuperation needed after prolonged sitting before lifting tasks
takes a long time; it takes 30 minutes or more after extreme flexion of the
back though about fifty percent is achieved within the first two minutes (p
· When a worker has to sit for prolonged periods provide lumbar
support to keep the worker’s back flexed; hence the worker should sit in an
upright position rather than a slumped one (p 181).
In summary a worker needs at least two minutes of recuperation (standing or
walking) after prolonged sitting and preferably 30 minutes. Workers who have
to do lifting task should be encouraged to sit in an upright position rather than
a slumped position.
Has anyone else published anything recently that I could quote? Has any
organization with authority and influence published anything that is apropos?
David McFarlane MAppSc (Ergonomics)
Ergonomist, WorkCover NSW
The views expressed above are those of the author and they do not
necessarily reflect the views or policies of WorkCover NSW. Any
recommendation concerning the use or representation of a particular brand of
product in this document or any mention of them whatsoever (whether this
appears in the text, illustrations, photographs or in any other form) is not to
be taken to imply that WorkCover NSW approves or endorses the product or
1. A Magora, (1972), " Investigation of the Relation Between Low Back Pain
and Occupation", Industrial Medicine, Volume 41, no. 12, December 1972.
2. D Troup, (1978), " Drivers back pain and its prevention ", Applied
Ergonomics, 9.4, pp 207 - 214.
3. P. Van Wely, (1970), "Design and disease", Applied Ergonomics, 1.5, pages
262 - 269.
4. Green J, Grenier, S and McGill, SM, (2002), “Low-back stiffness is altered
with warm-up and bench rest: implications for athletes”, Med Sci Sports
Exerc, 2002 Jul, 34, (7), pp 1076-81. See
5. Solomonow M, Baratta RV, Zhou BH, Burger E, Zieske A, Gedalia A,
(2003), “Muscular dysfunction elicited by creep of lumbar viscoelastic tissue”,
J Electromyogr Kinesiol, 2003 Aug, 13, (4), pp 381-96. See
6. Preuss R, Fung J, (2005), “Can acute low back pain result from segmental
spinal buckling during sub-maximal activities? A review of the current
literature”, Man Ther, 2005 Feb, 10, (1), pp 14-20, paragraph 5. See
7. Beach TA, Parkinson RJ, Stothart JP, Callaghan JP, (2005), “Effects of
prolonged sitting on the passive flexion stiffness of the in vivo lumbar spine”,
Spine J, 2005 Mar-Apr, 5, (2), pp 145-54. See
8. S. McGill, (2002), "Low back disorders. Evidence-based Prevention and
Rehabilitation", (Human Kinetics, Leeds), pages 171-181.