Here’s some video of a kid who strapped two sets of 10 lb wrist weights together using tons of duct tape to increase his deceleration training load. I can’t say I recommend it for most kids, but he’s the walking experiment around here, having gone from 71 MPH to 90 MPH in 10 months.
And yes, these exercises are very strongly influenced by Dr. Marshall. (Doesn’t seem to matter that I give him credit since his followers denigrate me anyway, but I’ll continue pointing it out.)
Always ready to experiment though…