(Hywel answering as Ariel is away on tour at the moment).
When she first started doing spanking, her bottom used to bruise quite badly afterwards. The main change we’ve noticed is that she no longer bruises as badly or for as long after even a hard spanking: the marks fade ore quickly, and don’t leave deep bruises behind the way they did for the first few shoots. She still plans spanking shoots last when she’s on tour in case, though.