Full lower body spasm....

I'm sure this has been talked about in here before but just wondering if this has occurred to anyone. I was in a race when getting to the last climb my lower body went into a crazy painful spasm. Every muscle at once, and sustained for what seemed like 5 min.. I just had to stand and absorb the pain as nothing I did seemed to help. It burned itself out, and my legs felt fresh. Finished the race. no pain and nothing the day after. Any comments