1. Opener/Kick
2. Jump
3. Scissor
4. Close Guard
Aikido Principles
-Base is a fighter's floor contact (foot/hand placement on the ground) as well as the distance their COG is from these floor contacts. Having no base means your tori has no floor contact, this is bad. For example in aikido the tori starts in a high-narrow base which is dangerous because it can be easily lifted or it's feet can be swept. It's common for openers to initially drop and widen the tori's base.
-Balance is a tori's horizontal distance between their floor contact and COG. For example the starting position is balanced because the COG is directly above the tori's feet on the ground thus resulting in zero horizontal distance. Break a tori's balance by forcing their COG outside of their base.
-Relativity between your base and your opponent's base can decide who is advancing in a fight. For example you want a low, balanced base relative to your opponent; or you want to have a high base weighing down an unbalanced opponent. It is difficult to break the balance of a low based opponent who has more than two floor contacts (two feet + hands) so it may be better to focus on controlling and removing these floor contacts.
-The Weak Plane can be defined as vectors connecting a tori's floor contacts and COG. You can break the opponent's balance by applying forces in directions perpendicular to this weak plane, where the tori couldn't make a base. The weak plane is always shifting but never disappears until your opponent loses their base.
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Ok then this bold part. Actually having no floor contact means your tori has no "base support", I mean, you can make your base by placing one foot on the ground, contracting other foot and using your hand grips to stay in balance. Or you can use your opponent as floor and step on him to be balanced. Hard but possible.
I'd say that the most accurate definition for balance is when your current position allows you to be mechanically stable, with no oscillations. Don't forget that you're balanced when you're lying down.
The definition you said is exactly what it takes to be balanced in a fight: "Maintain your cog inside your base support".
Base support is exactly the plain between your points of support, points of support can be both feet, both hands, one foot and one hand, both feet and one hand or both hands and one foot. Your COG must "fall" inside the base support in order to be balanced. Some examples of base support:
Also: I don't know if I got the definition of reserved movement, but I'll leave this replay of what I understood. If I'm right you can use it, if not, poke me and I'll search another replay. :v