I hope this is a valid question as I am looking for ways and means to translate some of your (and others) ideas into day to day sprint work.
I think I understand the time element but the question I have revolves around if when the “ground” contact is made in the running cycle makes any difference? Or is it strictly a matter of the length of contact time?
So for example relatively speaking if you are towing a sled during an acceleration the ground contact should happen in relatively the same body position as during an acceleration without resistance.
If you are doing step-ups, does the fact that your foot contacts the box (functioning as the “ground”) relatively “earlier” in the running cycle than “normal” make any difference? Since from observation I would say the “ground” contact on step-ups is longer than average since it takes more time for the athlete to be in a “completed” state. And if I can train the athletes to reduce that “ground” contact time on step ups, are the percentages good it will translate to reduced contact times during runs as well?
Thought I better pre-empt and clarify myself. Ground contact times are essentially determined by the rate at which one can move the centre of mass from when the foot touches the ground to when the foot can no longer touch the ground because of the fixed length of a leg. The rate at which one can move the centre of mass depends on one’s ability to co-ordinate the recruitment of muscles with the objective of moving the COM at the greatest speed. For this speed to be maximised, a compromise may have to be made between the force generated at each joint and the angular velocity of the hip, knee and ankle joints. That is why I think the step up with a clean/snatch would work better because one is encouraging the hip to extend as early as possible whilst the knee extends.
This concept might be more evident in the starting blocks if you concentrate on extending the hip as the first objective whilst pushing with the legs. See if that improves your 10m time at least.