One of the more difficult movement preparation drills - the quad stretch to toe touch - challenges dynamic stability on the stance leg, and mobility on the other leg.
In movement prep, a great drill that follows the high knee march and leg cradle is the quad stretch with hip IR walk. The natural flow of movement of the hip in extension is to rotate into internal rotation. Performing a walking drill over 10 metres, pulling the knee into flexion, hip into extension and applying a little hip internal rotation is a nice way to a) check that hip E and IR is comfortable, and b) lubricate the tissues into this pattern.
When a runner's trunk and pelvis position breaks down, send them back to the wall to assist stability. Cue them to press into the wall, which provides compression sensation to the mechanoreceptors in the spine, via the upper limb. This causes reflex stabilisation, permitting better mobilisation of the lower limb.
Maintain an isometric stance on the ground.
Start with isometric holds (great for achilles rehab) for 10-15 seconds.
Progress to alternating march.
Then to quick switches.
Add a "load and lift" - also part of achilles rehab (except for those who don't tolerate load at length), to check for single leg triple flexion force absorption competency - a great acceleration mechanics drill.
To drill acceleration mechanics