The lumbar fibres of iliocostalis lumborum
and longissimus thoracis are more angulated relative to the vertebral column than the multifidus or the upper erector spinae, with a substantial increase in obliquity towards the L4-L5 region (Macintosh and Bogduk 1991).
We are aware that we may also be interpreting signals from iliocostalis lumborum and multifidus and in this paper refer to the observed EMG activity as ULES.
The multifidus (a component of LLES activity in this study) has been reported to fatigue at a faster rate than the iliocostalis lumborum (Ng et al.
2002) Differences in electromyographic activity in the multifidus muscle and the iliocostalis lumborum between healthy subjects and patients with sub-acute and chronic low back pain.
Although some authors do mention the presence of lumbar muscles and fascia, specifi cally the quadratus lumborum, multifi dus and iliocostalis lumborum (Collee et al.
In fact different bands of the ligament appear to be derived from the quadratus lumborum and iliocostalis lumborum muscles (Bogduk 1997).