Asymmetrical lifting

Do you have some research or resources showing the spinal loads on asymmetrical lifting? Sounds contrary to what many PT's would do.It is a winning bet to do the opposite of what many PTs would do.Asymmetrical lifting challenges rotary stability in a very natural and reactive pattern. It is completely appropriate, and while I can not cite spinal loads, I would be comfortable in suggesting they are much lower than symmetrical loads given the inherent increase in challenge to stabilize. Less weight in the system would equate to less spinal load.