“Contracting the abdominals would result in a spinal flexion moment, partly countering of the extension moment produced by the erectors. This would result in a faster fatiguing of the erectors, a smaller net extension moment, unnecessarily larger compression forces, and possibly, less weight lifted. The rectus abdominis is an antagonist of the erector spinae; it would be, to be blunt, stupid to contract it, let alone to a large degree, in a movement that requires such a large extensor moment. The idea that the abdominals work to a large degree in movements like the squat and deadlift is not only unfounded and unsubstantiated, but is also unwarranted, as it does not make sense, biomechanically, to activate them in such a movement.” – Andrew Vigotsky
