If the drills are done properly (stepping down and just in front of the center of mass) you should be landing on the ball of the foot and utilizing the stretch reflex in the foot arch/achilles tendon. Dorsiflexion should be emphasized on the upward swing of the leg, but not overemphasized on the downward step. The foot will do what it is supposed to do. An overemphasis on dorsiflexion on the downward stroke can be problematic. Remember those devices that Seagrave promoted (the Dorsiflexor) that secured around your ankle and pulled your shoelaces up. What a load of horseshit that was (I’m channelling Charlie).
Kids should do the drills correctly and should be able to sustain the technique at the intensities you suggest. They may fall apart in their actual running, but that is why we are using the drills. Charlie described drills as either:
- Active - Used to teach athletes skills and develop the necessary strength to run.
- Reactive - Used to correct errors in running (i.e. fix your arm swing, emphasize stiffness during stance phase keeping the hip high, etc.).
In the case of kids, drills are primarily “Active” in application. As they get older and stronger, they will likely become more “Reactive” in nature.