I have several “annual physicals.” For my annual physical with our internist, I'm in a gown, opening in back. She just opens the gown while she's examining my lungs from the back. The gown is lowered completely when she examines my lungs from the front, and stays that way for my heart and breast exams.
My GYN has me in a paper vest, which opens in the front, and a lap drape. He auscultates my lungs from the back by inserting the steth under the edge of the vest. He sort of slips the front edges of the vest behind me when he listens to my lungs from the front and does my heart and seated breast exams. His heart and lung exams are cursory and he's not nearly as thorough as is the internist, but he doesn't need to be.
My endocrinologist does a more or less complete physical during one of the quarterly visits I have with him. It proceeds similarly to my annual physical from our internist for heart and lung exams.
I see my urologist two to three times per year in most years. He, or his PA, does a basic physical exam generally once per year. Again, for those visits, I am in a gown that opens in the back, but I know that I'm going to get the more complete exam if I'm asked to remove my bra when disrobing. The PA is more thorough than the urologist when it comes to the annual exam. Other visits are more focused on my urinary system and he doesn't typically do auscultation of anything other than my abdomen and femoral pulses, which is why my bra stays on for those visits.
In addition, I recently had orthopedic surgery, which required a pre-op physical. The orthopedic surgeon did the physical himself. He had my take off everything but my bra and panties and gave me a drape for my lap. He had me remove my bra for the lung and heart exams, did a very brief breast exam, then pulled the drape up over my breasts and bunched it underneath them for the rest of the exam.