Watch the technique on the stones. Last thing you want to get into doing is grabbing the stone from underneath when doing the extension. The stones are only light at this stage but as they get heavier you want to get them to learn to put their arms over the op of the stone and pull on it. Many a bicep can become detatched doing the way in the vid.
Small diameter stones dont help either, but it takes time to learn the technique. Good on you for having stones there any way!!
"There is no point being alive if you can not do the deadlift" Jón Páll Sigmarsson
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