Why is full planche much much harder than straddle planche?

[Deins Drengers]

Is the difference in leverage so big between those 2 ?

[Jon Douglas]

Yes

Unless a full planche is itself one of your goals (and its a good one), I have read several gymnasts saying that a) its not worth the effort invested for the points required, and b) that it's not worth the time invested for the strength payoff. This could get very blurry once you are past straddle pl on rings; someone like Coach would need to elaborate on that sort of situation. Read up on older posts by Dillon and Gregor if you are curious

Edit;

Gregor was in the situation of being able to sleep in maltese, but not being able to nail planche. Similarly Dillon achieved his malt by spending time training planches despite not having much interest in them at the time. Both agreed on the importance of planche training, even if you never get it for whatever reason, it builds habits and connections you need

Of course this is not to say that you shouldn't continue to work towards it as you go. Stronger is stronger, and without the competition factor we are free to strive for skills we want

[Jeremy Huston]

Bringing the legs together moves your center of gravity (CG) further away from your shoulders.  This has 2 effects.  

 

First, the shoulders need to generate more torque hold the body up.  Torque is force times lever arm length.  In this case force is body weight, and lever arm length is the distance from the shoulder to CG.  If the CG moves from the belly button to hips, that could be something like moving 10 inches to 12 inches.  That 2 inch change means a 20% increase in torque required to hold those hips and legs up.

 

Second, to balance you need to move your hands those same 2 inches to keep them under the CG.  Since you were already fully protracted and depressed in the straddle planche, the only way to gain those 2 inches is to extend your shoulder more.  This puts the shoulder in a position of decreased leverage.  Depending on body geometry, it could take pretty substantial extension to get those 2 inches.

 

So it's much much harder because you're putting your body in a position that makes it harder to generate torque and the same time that it needs more torque.

 

Disclaimer:  I am nowhere close to even a straddle planche (only halfway through F1), so I don't have personal experience to back this up.  Just my understanding of physics and physiology.