Active straight leg raise (ASLR) task. To create a
known mechanical perturbation to the pelvic ring, the ASLR
task was used. This task has been shown to have a strong
correlation with the mobility of the pelvic joints in individuals
with pregnancy-related pelvic girdle pain (16). Subjects
lay in supine positions with pillows under their heads. They
were instructed to lift their straight leg off the bed to
approximately 45° (ASLR), or to push their straight leg into
the bed as quickly as possible in response to a light. The
direction of movement was indicated by a differently colored
light in a choice reaction-time task. The onset of
movement was measured using a standard pressure biofeedback
unit (Chattanooga Group, Hornsby, Sydney, Australia)
sampled at 2000 Hz. Subjects were instructed not to keep
their leg in the test position at the completion of the task, nor
to attempt to return to the exact initial position. Subjects
were instructed to remain relaxed between trials. Data were
collected for 10 repetitions of the ASLR task, and data were
not analyzed for the task in which the leg was pressed
directly into the bed, as this task was not considered to cause
a significant perturbation to the pelvic ring. This was included
to make the task a choice reaction-time task, thus
reducing the potential for the subject to prepare for the
movement.
Pain and disability measures. Patients rated their
worst and usual pain in the last week and their worst groin
pain during their most common aggravating activities on a
10-cm VAS. Participants rated the functional limitation of
their groin pain of a five-point Likert scale ranging from
none (“groin pain doesn’t limit your activities at all”) to
completely disabling (“you can do very little activity due to
your groin pain”).