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The Effect of Experimental Groin Pain on Abdominal Muscle Thickness

Jansen, Jaap A. C. G. MSc* †; Poot, Bart BSc; Mens, Jan M. A. MD, PhD; Backx, Frank J. G. PhD*; Stam, Henk J. PhD

The Clinical Journal of Pain: May 2010 - Volume 26 - Issue 4 - p 300-305
doi: 10.1097/AJP.0b013e3181b8cde2
Original Articles

Objectives 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.

Methods 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.

Results 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).

Discussion 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.

*Department of Rehabilitation and Sports Medicine, University Medical Center Utrecht

Department of Physical Therapy, University of Applied Sciences Utrecht, Utrecht

Department of Rehabilitation Medicine, Erasmus Medical Center, Rotterdam, the Netherlands

Funded by the Netherlands Organisation for Health Research and Development (ZonMw; project number 7502005), the Hague, The Netherlands.

Reprints: Jaap A. C. G. Jansen, MSc, Department of Rehabilitation and Sports Medicine, H. P. Q05.4.304, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands (e-mail:

Received for publication February 6, 2009; revised July 15, 2009; accepted July 20, 2009

Conflict of Interest: There were no conflicts of interest

© 2010 Lippincott Williams & Wilkins, Inc.