The results show that TENS is significantly more
effective for relieving pain and increasing straight leg
raising than massage. The lack of significant improvement
in back flexion, however, is indicative of the
complexity of the back pain syndrome. It is not
surprising that activity in a particular set of muscles
is improved while that in another set is not. Nevertheless,
the highly significant correlation between
flexion and the PRI—the more sensitive of the two
pain measures10—suggests that flexion may be a complex
measure that is related to pain but as an index of
physical improvement is affected by factors that are
not understood.