Rupert Atkinson

If you have been practicing awhile, you will likely be touching on aiki in many of your ordinary waza. It just needs pointing out, realizing if you like, then you can target it for development. There is no magic. It is just the way you use you body and your and uke's energy. Not magical ki energy, just the power that you generate and that which your uke gives you, or you lure him to give you, to deal with. It is totally practical but most people just skirt around the edges because they are not directed towards it.
It will not make anyone invincible because most people that practice aiki do it in a very limited - nice uke - environment. Even the so-called 'strong attack' we do is so predictable you have to be a fool to believe it is anything close to real.
Just my 2c.