... basing this statement on the paper by Zermann et. al. (1999) which did find myofascial tenderness in 88% of Type IIIB chronic prostatitis / chronic pelvic pain syndrome patients.
(Chronic Prostatitis: A Myofascial Pain Syndrome? Dirk-Henrik Zermann, MD, Manabu Ishigooka, MD, Ragi Doggweiler, MD, Richard A.Schmidt, MD, University of Colorado Health Sciences Center, Denver: Infect Urol 12(3):84-88, 92, 1999)
There is therefore some good evidence to back up this statement.
This has also been found in a follow-up study:
"...Recently several researchers suggested that pelvic floor muscles might play a role [6, 7]. Zermann et al. [6] found that 88 % patients could not contract and relax the pelvic floor muscles and in their 103 patients 4 had a history of preexisting neurological problems and 37, of neurological or urological surgery. In our patients no patient was reported any neurological problem or urological surgery, but 52 of 62 (86.7 %) patients had pelvic muscle tenderness and spasm, similar to those of Zermann et al. [6], suggesting that chronic prostatitis / chronic pelvic pain syndrome itself but not neurological disease or surgery was the main cause of pelvic muscle dysfunction."
Source:
Biofeedback therapy for chronic pelvic pain syndrome
Zhang-Qun YE, et. al
Asian J Androl 2003 Jun; 5: 155-158
http://www.asiaandro.com/1008-682X/5/155.htm