Cortez
Tough but Fair
Lunging is an extremely useful tool which is sadly abused and rarely done well. I've lunged hundreds of horses, with sidereins usually (other gadgets only if required by people senior to me, many years ago): some horses I have lunged over their entire working lifetimes and have not seen problems occurring because of it. The science of motion fella is a bit dodgy and certainly a sensationalist/contrarian IMO.
If there is "lean", you're not doing it properly.
If there is "lean", you're not doing it properly.