The influence of experimental groin pain on abdominal muscle recruitment

Recent research has shown that longstanding adduction related groin pain has
several similarities with women suffering poost partum pelvic pain (Mens et al.
(2006). Tightening a pelvic belt increases adduction strenght en decreases pain
in about 70% of the athletes with adduction related groin pain. Richardson et
al (2002) heve shown that m. transversus abdominus is a important muscle for
pelvic stability, and anatomically represents a internal pelvic belt. Later
research by Cowan et al. (2004) has shown that m. transversus abdominus has a
dysfunction in athletes with longstanding groin pain. Since this study was
crossectional, it is not known whether the dysfunction is a results of, or
caused by the groin pain.
By experimentally evoking adduction related groin pain in healthy subjects we
can get more insight in this matter. Second, by evaluating the effects of
threat of groin pain, we can get insight in how any alterations in motor
control are organized by the central nervous system.
Hypothesis 1: Experimental groin pain leads tot changes in motor control of the
abdominal muscles.
Hypothesis 2: Threat of experimental groin pain leads to changes in motor
control of the abdominal muscles.

Goal 1: By evoking experimental pain we would like to investigate whether
abdominal muscle recruitment changes under conditions of experimental pain.

Goal 2: By threating with experimental groin pain we would like to investigate
how any alterations in motor control are organized.

The study is organized according to an experimental design, evaluating the
"within subject" effects of experimental (threat of) groin pain. Recruitment of
abdominal muscles is evaluated

Three tasks (rest, hip adduction, Active Straight Leg Raise) are asked during
three conditions (no groin pain, groin pain and threat of groin pain)

All echographic measures are taken in supine lying. Task 2 & 3 are regularly
applied in sports medicine to provoke groin pain in athletes (Cowan et al.,
2004; Mens et al., 2006).

Five repetitions are made per task per condition. Bad quality of echographic
pictures will lead to an extra repetition. Order of tasks is standardized. We
start with condition 1 (no groin pain). condition two and three are variated ad
random.

All measurements are performed by a single person, to prevent inter-observer
variation. All images are digitally stored and judges by an observer blinded
for task and condition.

For more details I refer to the research protocol chapter 6.

The extent of the burden associated with participation are considered
reasonable. During the first condition, load for the participant is minimal.
During the second and third condition, load is reasonable. By evoking pain
using electrostimulation, pain can be switched on and off, so the subject will
not experience pain when nothing happens.

There are no risks for the subjects in participation