View Full Version : Re: Flat back paradox

02-01-1998, 08:46 PM
There is a good discussion of the old question of whether or not to
lift with a straight back in Stuart McGill's recent paper:

McGill, S. M., The biomechanics of low back injury: implications on
current practice in industry and the clinic. J. Biomech. 30(5)
(1997): 465-475.

He argues that the interspinous ligaments, which are angled anterior-
posteriorly in order to limit the posterior sliding of the superior
vertebrae, produce a large anterior shear force when the spine is
fully flexed and the posterior ligaments are taut. This shear force
is potentially far more damaging than the direct compressive force on
the discs. His conclusion, therefore, is that one should avoid
lifting with a fully flexed spine, but lifting with some degree of
flexion may well be appropriate depending on the
size and position of the object. The priorities are to make sure
that the load is as close to the body as possible, minimising the
moment arm about the spine, and to avoid full flexion of the spine
and involvement of the posterior ligaments.

Best wishes,


Dr. Sam Evans,
Medical Systems Engineering Research Unit,
UWC School of Engineering,
PO Box 688, The Parade,
Cardiff CF2 3TE, UK.
Tel. (01222) 874533 or (01222) 874000 x5926
Fax. (01222) 874533