Sorry to necropost, but I wanted to help a bit with this.
1. Lengthen your warm up and cooldown. It's never a good idea to do a sprinters workout without at least 10 minutes on either end. You'll hurt yourself, and end up much more sore (because of the lactic acid buildup) than needed.
2. Personally my training has always been using distances rather than times. If you have access to a 400m track, then do some 3200m On and Off, or some low rest Strider exercises. For the On and Off you sprint the straight lengths (90-95%) and cruise the corners (65-75%). The Strider exercises are 85% 80m sprints with a jog the rest of the straightaway, turn and do it again.
3.NEVER STOP MOVING. Don't ever sprint for 30 seconds and then just stop and sit there for 1:30 letting the lactic acid buildup and make you tight and sore.
4. Add a dynamic stretch to your workouts, and do mobility drills. These help you loosen up, improve range of motion, and overall fitness.
Trust me on this, its more healthy and much better for getting in shape.
Using these exercises I made all-state X-country,100m 200m and 400m Track and Field, and even all state Swimming.
Good luck.
