Discipline

recently we have been having major behavioural issues with our 3 1/2 year old daughter. She is extremely defiant and disrespectful to us. She acts in ways I wouldn't have dared to until I was a teenager. Her behaviours include things like kicking, hitting and spitting at us, in addition to calling us things like nasty and bad. We always tell her this behaviour is not acceptable and we put her on the naughty step-but this consequence is almost a joke to her. She laughs and runs away from her spot. We are really at a loss and have no idea what else we can do to make her realize this behaviour is not acceptable. We are looking for something to teach her proper behaviour and respect for us and others in general. Someone suggested putting her in martial arts. I am really keen on this idea but also worry this will teach her the  skills she needs to further hurt us. Those who have taught martial arts are of course pro to the idea and then there are those who say kids who take martial arts are often the "behaviour" kids. Oh what to do??? Maybe this is just a phase that will end really really soon...let's cross our fingers we all make it through without too many scrapes and bruising.