Hi. New to the forums, but this occurrence has been bothering me. This morning, in ROTC, (I'm a 15 year old male, by the way), we were standing at attention for just 20-25 minutes while the instructor was checking uniforms. I began feeling nauseous for about 15 minutes, but didn't think anything of it. Then, suddenly, my face felt hot and my vision grayed out to nothing and I couldn't hear more than a soft muffle. I was still fully aware of my position, however, and was able to crouch were I was. After a minute, my sight and hearing slowly came back, and I was able to get water. This has never happened to me before, and my friends are telling me it was because I was standing with my knees locked, which I think I was. Any help would be much appreciated. Thanks in advance!