First of all, if it's not already quite obvious, I enjoy wearing a jockstrap and also seeing other guys wearing one. And if you've read some of the medfet stories that I've written (shameless plug here: https://www.literotica.com/stories/memberpage.php?uid=1264188&page=submissions), you'll realize that I also like to feature them in my stories. All of that means I've spent a good deal of time fantasizing about and generally pondering scenarios where you might end up in a jockstrap during some kind of medical examination. I obviously love that scenario because it nicely marries my two fetishes: medfet and jocks!
Given the fact that I wrote these stories to scratch my own fetish itch, they probably represent some of my best ideas on ways to include strap wearing with a medfet scene.
Out of the six stories I've written (so far), these two are the only ones that don't feature jockstraps:
Jim's Camp Counselor Exam
Jim's Insurance Exam
All of the others feature them to some degree.
Jim Goes to Boot Camp is about a boy receiving an entrance physical exam as he is beginning his sentence to a boot camp punishment facility. The jockstrap isn't introduced in this story until his medical exam has already been completed. He's given a strap to wear (and nothing else) as he's taken to meet his drill instructor. The story doesn't indicate that the strap is brand new, and he's told that all the boys in the boot camp wear them. So in this story it's implied that he's actually wearing a used (but clean) strap. There's no real reaction from him at the thought of wearing a used strap, since he's already upset by the exam that he just had to endure and the thought of having to put on the strap.
Jim's Group Physical is about a group of high school boys that receive a group physical exam at school, administered by the school nurse and a visiting NP. The twist to the story is that this exam takes place during their regularly scheduled physical education class, and so they are wearing their P.E. uniforms to the exam. Of course the uniform includes a mandatory jockstrap in place of their regular underwear. In this story, the boys obviously have worn straps before (they do so during every P.E. class), so it's not as if they are putting one on for the first time, or wearing one that was worn by someone else. But the exam is very embarrassing for them since most of the exam takes place with them in just their straps and nothing else.
Jim Goes to College is about a freshmen in college who receives a group sports physical. The exam is done in a very large group with all other males that are planning on participating in a sport. Since the exams are specifically for sports, and it's only for males (female exams are on another day), everyone being examined is instructed to undress completely and put on just a jockstrap that is provided for them. As Jim (the main character) examines the strap he was given, he concludes that it was clean and in good condition, but certainly not new, and had probably been worn by several dozen young men just like him! And since Jim had worn one for sports in high school, wearing one now wasn't a new experience for him. But certainly walking from exam station to station in the gym dressed only in this used strap, and seeing all of the other guys dressed exactly the same way, that was all a new experience for Jim. At the end of this story, Jim decides to keep his used jock as a souvenir. We are left to our own imagination as to how Jim will utilize that strap later.
Jim's 1st Day of Physical Education tells the story of a high school senior (Jim) along with 16 other boys who experience the first day of P.E. under the leadership of a rather arbitrary and abusive female teacher. The story follows the boys as they are instructed in the class procedures, stripped in order to receive a brief medical exam by the school nurse, and then participate in a condensed class that includes some exercising, some discipline, and group showers. Of course part of their required class uniform is a new jockstrap which they all receive during the orientation. And since it's the first day of class and the boys haven't yet purchased their full P.E. uniform, the exercises and other activities take place with them wearing just their straps! Most of the boys indicate that they've never worn a strap before, so part of their orientation includes instructions (and a demonstration) on how to wear one.