Leverage with the ground isn't needed to throw a ball, it does stop the backwards momentum from throwing the ball moving you backwards.
How come I can jump up and throw a ball in the air.
And why wouldn't muscles work in space.
You can jump up and throw a ball in the air because you are using atmospheric pressure as your leverage, only you won't get as much leverage as opposed to your entire body being pushed to the deck by it's own mass acting against the atmosphere and the actual solid ground.
And muscles clearly couldn't work in your space but that's not what we're arguing about, so let's pretend they can in your fantasy near vacuum.
I want you to seriously think about what I say here. I very much doubt you will. In fact I'm 100% sure you will just go total cloud cuckoo but I'll hang onto the hope that real people with real brains can see the reality.
Ok, get a large board; say: a 4x4 foot ply-board. Stand on a skate-board and throw that ply-board away from you and see how far you're repelled backwards. You'll find that it's quite a bit if your skate-board is on a hard smooth surface with good wheels.
So what happened?
It depends on who you ask. You can ask a severely indoctrinated naive person who will tell you that the mass of the board is what propelled you but a little help from air resistance due to the surface area of that board.
Try the same thing in water and tell me what repels you?
Let's take the board into fantasy space, held onto by magical floating man on his skate-board.
As we can see, the skate-board is useless because there's no floor.
The man standing on that skate-board can exert no pressure upon the board nor can the board exert any back. Basically his feet are touching the board as the board is touching his feet.
He holds the 4x4 board and realises that he feels no force against his muscles because that board is also floating just like he is.
His arms are bent as if he is about to launch the board away from him, so how does he do this.
If you think he can just push his arms out and release the board you have to understand action/reaction in equal terms and understand that in a weightless floating environment like we are told space is, you have to use your common sense and grasp that both the person and the board create no extra resistance because there is no environment that caters for resistant force.
At this stage you get some of the so called clever shits that will say "ahh but they still have mass in space." It's tedious but let's counteract that by giving the man and the board exact mass.
Ok before I move on I want any person to throw as many objects as they feel necessary from the ground and also from a skate-board or some wheeled contraption. Even do it jumping in the air and also hanging from a rope.
All I need for you to understand is the fact that no matter how you do it, you have to have leverage to create a force and that force will be equally counteracted by a reactionary force, because of the atmosphere you live in and all things in an atmosphere have mass/density.
The reason they have mass/density is due to the make up of whatever matter/object pushing against a pressure of it's own displacement of that atmosphere.
In fantasy space you have nothing to lever against. No walls to push off and no floor to stand on. You are literally in suspended animation in a way.
Now because you do not have anything to lever off of, you can only apply enough force to actually stretch out your arms against that board.
What are you not doing?
You are not exerting anything onto the board any more than the board is exerting back onto you.
You are left with outstretched arms touching that board and that's it. None of you go anywhere from this point.
You end up with your fingertips touching the board and your toes touching the skate-board.
It's pretty simply for any logical person to work out but too many would rather tread the path of bullshit told by people who are too afraid to lose their jobs, as well as those who are actually paid to promote the utter shit of space.