The problem with most rotational movements is that they produce shearing forces on your lumbar spine. One of the foundations of biomechanics is that you don’t place your spine into a simultaneous state of rotation, flexion, and side bending, and you especially don’t add an external load.
This eliminates a number of popular abdominal exercises such as dumbbell side bends and the twisting abdominal machine. Exercises like the Russian twist should be performed with care, making sure that the trunk is flexed rather than the spine.
There is a quick and easy solution to the inherent problems with twisting exercises – don’t twist.
Enter: The Pallof Press!