What are you seeing in these diagrams? The same amount of load (1.2 kg/2.7 lbs) but arranged differently around the midline. Well, we’re playing with rotational inertia again but it is around the longitudinal axis (LA) the blue line on the figure. Remember the formula for rotational inertia – I = mr2, the resistance to angular motion a function of mass (m) and how far the mass is from the axis of rotation (r).  

Which loading pattern will make it harder to rotate the core around the LA? Note that most of the mass in the teardrop weights in A are arranged closer to the centre line/LA (small r2), whereas in B the mass is arranged further away from the LA (larger r2). As a result, B loading has greater rotational inertia/resistance to angular motion, that is the core muscles will have to work harder to rotate the trunk around the LA. Technically speaking, it is transverse plane strength training of the core around the longitudinal axis.

So, what are the implications? Do you have athlete’s that have excessive rotation in the core whilst running?  Do you want to engage in high velocity core training whilst sprinting? For athletes that need rotational power in the core, can you movement specific strength train with B loading?