I've been doing the doggcrapp training, and tonight was doing ez bar concentration curls with the slow negatives, and my forearm tightened up. I stopped and when I got home flexed it and it got real tight and basically is in a constant flexed position. I massaged it down, it still feels alittle tight but better and I can flex it again without it swelling up. Anyone know what's going on? I had a similar occurence last week with my tricep, and since then everything has been fine.