i've had a few instances where i thought i had a concussion. one was in a hockey game and i got completely leveled. it was a really really late hit and i had no idea it was coming, kind of from behind. i slammed my head in the ice and laid there for a good 10 seconds and then tried to get up. i had a rediclous head ache and couldnt skate straight. also, my vison was blurry and i was pretty nautious.
another time was when i was skiing and a snowboarder fuckin hit me. it was my fault though. there was a ridge and i skiied across it slowly so i could wait for a friend on one side. it was a open groomer. before i knew it, didnt even see it, i was like 3 feet in the air, laying horizontally. apparently i blacked out since i didnt remember being hit or being in the air. i laid theyre for like 15-20 seconds and woke up questioing my friends why my skis and poles were like 20 feet away. my friend was luaghing cause i just got leveled so hard haa. then i see this snowboarder thats apologizing. so i say im ok, even though i dont even know what happened. again i had a really bad headache and blurry vision. i didnt throw up either times though.