The effect of experimental groin pain on abdominal muscle thickness

It is not clear whether abnormal abdominal muscle behavior in athletes with longstanding groin pain is a risk factor for groin pain or is caused by groin pain itself. Therefore, this study investigated whether anticipation of experimental groin pain influences abdominal muscle behavior.

In 14 healthy athletes, abdominal muscle thickness was measured using ultrasound under conditions of anticipated groin pain and acute groin pain. Groin pain was induced using superficial electrical skin stimulation. Tasks evaluated were isometric hip adduction and active straight leg raise (ASLR) left.

The m. transversus abdominis and m. obliquus internus showed a significant decrease in thickness during "anticipation of pain" compared with "no pain" and "pain" during both hip adduction and ASLR (P values <0.04). For m. obliquus externus, a significant increase in thickness was found only during "pain" compared with "no pain" and "anticipation of pain" for ASLR (P<0.004).

If ASLR or hip adduction is associated with anticipated groin pain, abdominal muscle behavior is different from a pain-free situation and from a painful situation. These results suggest that abnormal abdominal muscle behavior found in athletes with longstanding groin pain may be caused by a pain anticipatory motor strategy. This may have implications for rehabilitation.