Spontaneous contraction pattern of the Transverse Abdominal muscle in pregnancy-related low back pain

The incidence of low back pain is high. In 85% the cause is unclear. In those
85% the back pain is labeled as non-specific, and causal treatment is
impossible. Research has shown that the contraction pattern of the transverse
abdominal muscle (TA, the deepest of the three muscles of the lateral part of
the abdominal wall) in patients with non-specific low back pain differs from
that of subjects without low back pain. Investigations by means of EMG have
shown that in patients with low back pain TA contraction is delayed. It seems
credible to assume that this changed contraction pattern reduces the strength
of the pelvic ring and the lumbar spine and seems to be one of the factors that
causes delayed recovery of back pain. In diagnosis and treatment a need exists
for a patient-friendly, reliable, sensitive and specific method to check the
contraction pattern of the TA in subjects with back pain. Currently the
judgment of the therapist is based upon inspection, palpation and sonography of
the abdomen. Reliability of inspection and palpation are low. Sonography to
measure the thickness of the abdominal muscles is very reliable. However, the
thickness at rest in patients with back pain is about the same as in controls.
Some studies show a difference of TA thickness of patients compared to controls
in special test situations e.g. during a drawing in maneuver of the abdomen.
Problems are 1) the differences between patients and controls are small and 2)
some other studies are not able to confirm the results.
The studies of the TA by means of ultrasound in patients with back pain show
several drawbacks such as: possible confounders as cause, duration and severity
of the pain are not considered, controls are recruited from a different
population than the patients; contraction pattern of the abdominal muscles is
studied at rest and/or after the instruction to tense the abdominal muscles
instead of the spontaneous contraction pattern during activities which burden
the lumbar spine. In the proposed study attempts were made to cope with these
shortcomings. It is also for these reasons that de study focuses on back pain
during pregnancy. Primary the study is explorative. In further studies the use
of possible positive findings should be tested in other patients groups than
pregnant women.

Primary research question part 1:
"Is it possible, to find a difference between the contraction pattern of the
abdominal muscles measured with ultrasound between pregnant women with and
without low back pain?*

Primary research question part 2:
"Is it possible within a group of pregnant women with low back pain to find a
correlation between the contraction pattern of the abdominal muscles measured
with ultrasound and severity of back pain and disability?*

Secondary research question
In a subgroup analysis part 1 of the primary research question is asked again
for patients with severe pain in combination with positive scores for pelvic
girdle pain.
So:
"Is it possible, to find a difference between the contraction pattern of the
abdominal muscles measured with ultrasound between pregnant women with severe
low back pain and positive scores for tests for pelvic girdle pain and controls
without low back pain and negative scores for pelvic girdle pain?*

Cross-sectional study

1. Examination: 5 minutes
2. Ultrasound examination: 10 minutes
3. Fill in questionnaires: 5 minutes (healthy control)-10 minutes (patient)
The investigation is hardly irritating and is without any risk.