I've seen a lot of people who swear by certain exercises, such as pistol squats and hanging leg raises to name a few, which seem impossible to do without rounding (de-arching, if you will) the lumbar spine. I also hear many people (who seem to know what they're talking about), saying to never ever ever round the lumbar spine. WTF is up? I'm not trying to catch anyone contradicting themselves, I just want to know what is correct and whether or not pistol squats and hanging leg raises will be detrimental to spinal stability/health. Thanks for any advice/info. I have googled and come up with little info to satisfy my curiosity.