An erection begins with sensory and mental stimulation. During sexual arousal, nerve messages begin to stimulate the penis. Impulses from the brain and local nerves cause the muscles of the corpora cavernosa to relax, allowing blood to flow in and fill the open spaces. The blood creates pressure in the corpora cavernosa, making the penis expand and creating an erection. The erection is maintained by contraction of the ischiocavernosus muscle, which compresses the penis against the ischium (the curved bone forming the base of each half of the pelvis), obstructing the blood flow through the dorsal veins. As such, weak pelvic floor muscles make it hard to get and maintain an erection. Also, ejaculation is caused by involuntary contractions of the bulbospongiosus muscle. As such, with a weak pelvic floor, you don’t have the necessary muscular control to prevent the involuntary muscle spasms and resulting ejaculation. In conclusion, weak pelvic floor muscles usually result in both erectile dysfunction and premature ejaculation.