If you were to do a sit up, which loading pattern would overload and strengthen the core more A or B? Both vests have 800 grams of additional weight on them. I'm picking most of you would've chosen B. But can you give the reason?
In A the load/mass is arranged close or proximal to the axis of rotation, which runs through the hip.
In B the load/mass is arranged further away or distal to the axis of rotation. So what?
Can you remember that formula for rotational inertia – I = mr2. Rotational inertia is the resistance to angular motion which is a function of mass (m) and the distance of that mass from the axis of rotation (r).
In B the same mass is further away from r the axis of rotation, and therefore is lot harder to move i.e. r gets squared.
So if you want to progressively overload your core workout you can put more mass on the core or shift the loading from proximal to distal and get rotational inertia working for you.