Right, the transition from the starting angle to the fully upright position does present an interesting challenging because, by definition, no two steps during this phase feature the same angle of extension.
Like Charlie, I’ve made it a point to limit the amount of cues I give during actual sprint training and save them more for the drill work.
In my experience, as far as the actual sprint work goes, I’ve relied upon ‘let it happen’, ‘head in line with spine’, regarding upright sprinting: step over/down, downward arm action, vertical action and more ‘pushing’ during early acceleration. I’ll typically reinforce up to 2 verbal cues throughout any single speed session.
Obviously the bulk of my players spend the majority of time in starting, re-directing, and acceleration during a game so the bulk of our volume is spend in the acceleration distances.
So as far as cues directed towards the transition from early acceleration to upright running, thus far, I’ve relied upon ‘let it happen’ , ‘head in line with spine’, and ‘knee through’ such that the transition from angled to upright happens smoothly and incrementally from stride to stride.
No doubt a work in progress particularly considering the fact that most of my guys have their mind on football not track.
Along those lines, one of the many Charlie quotes that comes to mind is “what matters in the end is sport performance, not maximizing the training components for their own sake”