Over the knee spanking is one of the most basic forms of humiliation and domination. Being in that position is such a submissive role, that the person can't help but feel totally humiliated. Bare hand spanking over the knee takes things down to the root level of discipline, harkening back to memories of moms otk spankings. Over the knee hairbrush spanking jacks things up a notch by adding a bit more "sting". But spanking OTK is still degrading and humiliating to the recipient. Some couples use erotic OTK spanking to spice up their sex lives.
Women spanking men is a very common scene at the S&M clubs and dungeons all over the world. It's easy because all that's required is a lap and an ass.
Adult spanking over the knee is utilized by many as foreplay. Femdom OTK spanking my be admininstered by your partner or a trained professional, but it has the potential of the same results... the recipient is turned on. For some people, both men and women, memories of moms hard OTK spankings have served a stimulation for their masturbation ever since puberty. As their spanked bottoms are paddled they redden and heat up... but that's not the only thing that is getting blood flow.