My main event is the 400m. I never have this problem with the 400 or 200, just the 100 and to some extent the 55.
Basically, I find that when I get into an upright sprinting form from blocks (as opposed to a gradual build-up, or something like a 30m fly) sometimes, (most of the time, not always) I am unable to get into my stride properly.
For example, last night I ran the 100m in a race. I had a decent block start, but when I got into my upright running form I could feel my heels coming up way too high behind me and my knees dropping too low in front of me. In the moment, I felt like I couldn't do anything to adjust my form. I stayed loose and didn't panic, but still ended up running pretty poorly.
Like I said this never happens to me in the 200/400, probably because of that lacking sense of urgency you get in the 100. It also never, ever happens when I start from an upright position. Sometimes I am able to transition from driving to upright properly, that's when I run my best races obviously, but it seems to happen less than 40% of the time and I don't know what triggers it.
Has anyone ever heard of this problem before? I'm thinking some mental cues to focus on would be helpful. Any tips would be much appreciated.