My twin boys are 11 month old. They have a habit of throwing their head back and arching their spine by bending backwards. This is how they show their irritation and throw tantrums. I’m horrified as they do this whenever and wherever they are. They hurt their heads backside as they suddenly fall backside with force on ground or wall. I am careful most of the times but still couldn’t control them because of this behavior. Kindly suggest how can i change this habit of them.