I had a little pain in the pelvis region (iliacus muscle) and i have fitness class so i warmed up with my friends did 3x400meters. Then we were gonna do 100 meter sprints. I did the first one, and on the second one * my iliacus muscle just poped and i collapsed(theres no internal bleeding) i can walk a bit but its very painfull lifting my leg (in hip) it makes 54 hours.