For many of us who sit during the day this exercise will take the pressure off of your discs and help lengthen the spine. Not a good exercise if in pain or if you have tight lower back muscles, as this is shortening them further as they are contracting! For those with rounded backs, flexed spines and bulging discs, this is a good option and should feel good! If it does not don’t do it!
Try performing after sitting for long periods, i.e driving!