not sure why you are getting worse but when you do sprint work are you only doing block work? Sometimes it helps to mix it up and even though as you progress to closer to the season you should do more block work it doesn’t hurt to have accel or sprint sessions in general where you do sprints from 3 point, 4 point, crouch etc. and stay away from the blocks. My block starts do seem to go to shit to some extent when I am at a meet also and it’s like I forget what I’ve done in practice but I think having practice sessions with other people where your both doing blocks at same time gets you use to meets if you have that luxury. Anyways goodluck and I hope you figure it out.
