I am a 27 year old male recruit and I have to take a physical fitness and strength exam next week for the first time, at my army facility's training center. The test involves doing five sets of calisthenics (sit-ups, push-ups, crunches) and low crawls back to back, each broken up by jumping jacks. What surprised me is that my friend mentioned that he took it with a group of 10 other guys in a gym and all of them were required to strip down to their underwear and socks for this, and leave their clothes in an adjoining locker room. I have never had to do calisthenics and jumping jacks in public in just my underwear and socks before, so this seems a little humiliating. I also only own tighty whitey briefs, so would it be really embarrassing if I had to do the calisthenics in just these white briefs? A more embarrassing question: I am worried that during jumping jacks or the low crawl, the friction from my briefs will give me an erection. What should I do if this happens and is it common for guys?