I'm about to really call myself out here, but I — someone of sound mind and with a vagina — love to pee in the shower.
Now, I was already well aware that peeing just in case and squatting over the toilet aren't the best, but when I saw that peeing in the shower — one of my few pleasures in life — is also considered a bad habit, I was like, "Excuse me???"
I decided to reach out to Alicia for more info on why she advises against peeing in the shower. First things first, Alicia is a certified pelvic floor physical therapist with a doctorate in physical therapy, so she knows what's she's talking about here. One of the first reasons she cited is that peeing in the presence of running water can actually lead to a psychological effect where you associate the sound of running water with the urge to pee.
"Your bladder relies on signals it gets both from the stretch of the bladder walls as it fills, as well as signals from the brain which let it know when to contract to urinate. We want to avoid training our bladder to associate certain signals with the urge to pee. In this case, peeing in the shower associates the sound of running water with urination or with submersion in water. This can often transition into being triggered by other sounds of running water (like when you're running the faucet to wash your hands or the dishes) or when you're in bodies of water."
"For some, this may just be an annoyance, but for people with any kind of pelvic floor dysfunction, this could contribute to urge incontinence (or leaking urine when you have the urge to use the restroom)."
Alicia also mentioned that for those of us with vaginas, our pelvic anatomy simply isn't built for peeing in the shower/standing up. "From a pelvic floor perspective, the position for peeing in the shower in not conducive to pelvic floor relaxation. AMAB (assigned male at birth) bodies have the prostate to support the bladder, which makes standing to urinate okay, but AFAB (assigned female at birth) bodies — as well as people who have had affirmation surgeries — do not have the same level of support for the bladder."
"To maintain continence (i.e. not peeing your pants at inappropriate times), the pelvic floor generally wants to remain contracted in a standing or hovering position, so to urinate in those positions, one has to bypass these normal continence mechanisms, which can be problematic down the line."
"Deep squatting all the way to the ground in the shower avoids this and allows the pelvic floor to relax, but then you're still doing the water/peeing association."