|
Magnusson M. and Pope M.
Iowa Spine Research Center, Dept. of Orthopædic
Surgery University of Iowa, Iowa City, IA
Introduction: Low back pain has been shown to be related to
occupational exposures in numerous studies, several of which
dealt with nurses who have major lifting demands. Pre- vention
measures have included ergonomic redesign, worker selection based
on strength testing for example, exercise programs and training
in safe lifting practices. However, successful interventions
are few, resulting in considerable interest in the prophylactic
use of lifting belts. This study looks at whether back belts
increase the maximum voluntary contraction (MVC) force without
increasing electromyography (EMG) and if back belts increase
the endurance of the dorsal muscles. Subjects were five males
and five females all free of low back pain.
Methods: After a rest period in the lab, subjects performed
isometric lifts to the MVC point with legs slightly flexed. A
number of lifts, both without a back support and while wearing
a wide elastic lumbar support were made while being measured
with EMG electrodes. Comparisons were made between tests with
and without the lumbar support. At the conclusion subjects were
asked if the support helped to stabilize their trunks and if
it helped them to lift easier.
Results: The proportion of MVC-EMG to MVC-exerted force was
calculated for each trial and each subject. There was a significant
decrease in this ratio when the support was worn compared to
no support. "All subjects, except for one male, answered
that the support helped to stabilize their trunk and that it
helped them to lift easier. . .This could perhaps suggest that
back supports could be helpful in very heavy lifting situations,
i.e. nursing tasks. A constant MVC force was generated with lower
MVC-EMG when the back support was worn."
Conclusion: "In this study of isometric lifting it was
found that a back support reduced dorsal EMG and was associated
with subjective assessments of improved stability and enhanced
lifting capacity."
"Laboratory measurements showed the back support
reduced dorsal muscle activity during lifting and subjects reported
improved stability and easier lifting."
Marianne Magnussen, PhD, PT
Personal communication. 1994. Submitted for presentation.
(Review by Chase Ergonomics approved by authors, July 1996.)
|
