I've done 4 sprints in the last month consisting of 8x20 second runs.
The first one I did on the treadmill, no problem. The second one I did on the track, after the 3rd set I got a little cramp in my quad but pushed onward. Then I tried playing racquet ball and found that any time I exert a lot of energy on my left quad I feel the cramp/tear, but when I am just walking around I don't feel it. I took off all extreme exercises for the week and healed up pretty good. The 3rd set didn't cause me any trouble, but then today I tried again, and in the first sprint I felt it, and I stopped after on 3 sprints, hoping that I wouldn't take as long to recover.

I did stretch (grok squat, quad stretches) and I did warm up with some joggings, so what's the deal here? Am I missing something nutritionally? Am I not warming up enough? Should I stay off it until it's completely gone or can I still play racquetball?

Thanks already, I know you guys will have some good info.