Lax uterosacral ligaments diminish the contractile strength of pelvic muscles which contract against them. a Upper figure: the weak USLs elongated to e, result in elongation of LP and LMA (which contract against USLs) also to “E.” Loose USLs weaken muscle forces of LP and LMA needed to open the urethra. b Lower figure: interpretation based on known sarcomere physiology according to Gordon [21]. Striated muscles (LP/LMA) contract optimally over a short length only of the sarcomere (L, red rectangle). Elongation of muscles to e (black rectangle) cause rapid loss of contractile muscle force needed to open the urethra. If loose USLs weaken the LP and LMA muscle forces needed to open the urethra, the detrusor must contract against an unopened urethra, with higher pressure, prolonged flow, high residual.