We're going to get a lot of core engagement and our upper body working because we're moving the arms. (weckmethod.com)
Only this time, there is much more core engagement because of the off balanced position your body is put into by the placement of the anchor point. (onnit.com)
You'll also get some bonus core engagement because of the location of the weight in relation to your body. (thrivepersonalfitness.com)