Jo and aikido go together like peas and carrots. But what kind of jo? There are several jo systems that various aikido classes use as an adjunct to aikido, including
- Shindo Muso-ryu Jojutsu (developed feudally)
- ZNKR Seitei Jo (developed 1968)
- aikijo and aikiken (developed pre-war by Ueshiba and formalized in 1973 by Saito)
One distinctive feature of Aikijo is its pair of extended, solo kata titled (uncreatively) the 31-step kata and the 13-step kata. Seitei Jo does not have this sort of prolonged solo forms and from what very little I've seen of the Koryu Jo, neither do they.
31-jo kata is interesting as an exercise when you do not have a partner because it provides a method of practicing some of the same kihon as found in Seitei Jo - but within a context of aiki-like movement. The Seiteijo kihon that are easiest to identify in 31-jo kata include:
- tsuki (both honte and gyakute)
- hikiotoshi uchi
More kihon analogous to stuff in Seitei Jo are probably in 31-jo kata but I just haven't been able to find them yet. In any case, 31-jo kata makes for an interesting solo exercise when you don't have a jo partner available to help keep your jo skills honed.