All aikido uses Ki. Ki can be thought of as an inner power which is not based on a person's normal physical constraints. Whether the practitioner explains Ki in spiritual terms or prefers to consider Ki as just a natural progression of increased focus and clarity of thought within the technique is unimportant.

Most forms of aikido believe Ki is learned automatically by practising aikido. Ki aikido has developed techniques to aid the learning of Ki, deliberately using successively harder tests to help the student learn to perform well under pressure. These tests are structured so that although the practice is challenging, they remain within the limits of the practitioner's ability.