Aikido training involves practicing techniques with a partner. The nage is the partner who is performing the techinque, while the uke is the partner who is attacking and thus receiving the technique. Uke and nage must be equally engaged in the training, and both must be practicing their roles while training.
The purpose of partner practice for the nage is to refine the execution of the technique, while also developing their awareness of their uke’s balance and power, and learning to judge how much speed and power is appropriate to put into the technique with any given uke.
For ukes the purpose of partner practice is much more subtle. A good uke will always attack with intent – not necessarily speed and power, but with a committed attack that is intended to defeat the nage. Once the attack is dealt with by the nage, the uke must stay engaged with the technique, remain connected to the nage and always be looking to return to hanmi (basic stance) if the nage releases the technique. By remaining connected to the nage, and always looking to return to hanmi once their balance is lost, the uke forces the nage to perform techniques correctly, learns to be aware of their own balance and center, and is able to take advantage of weaknesses within the nage’s technique. A committed and intentional attack is required to force the nage to respond with the correct amount of concern for their personal safety. A weak attack does not required a proper response. The committed attack is also teaching the nage what a proper attack looks and feels like.
Both uke and nage must also practice zanshin – of being aware of themselves and their surroundings. This is about knowing what is happening around you so that as you throw, or are thrown, you know where the uke is going to land, if it’s safe for them to land there, and is their anyone else who will also be landing there. This must be done while focusing on the technique you and your partner are practicing. For beginners this is about safety and looking after your training partner, for senior students this is practice for dealing with multiple attackers.