Pelvic floor weakness is the direct cause. The pelvic floor muscles act like a hammock supporting the bladder, urethra, and other pelvic organs. When these muscles weaken — from childbirth, aging, hormonal changes, or chronic straining — they can no longer fully compress the urethra during moments of abdominal pressure (coughing, sneezing, jumping).

Urethral support depends on both muscle tone and tissue quality. Even a small loss of support at the bladder neck allows urine to escape during pressure events. This is why stress incontinence often worsens gradually — progressive muscle weakening and tissue thinning compound each other.

Why Kegels aren't enough for most women: Kegel exercises target the right muscles but at very low intensity. Studies show most women perform Kegels incorrectly, and even when done perfectly, voluntary contractions don't reach the supramaximal intensity needed to rebuild significantly weakened muscles.