How do you lock a bone in 3D space during animation?

Question

I am trying to animate things like a boy jumping up to monkey bars, grabbing them, then swinging around. I've been able to rig an armature with IK, no problem. I figure I can cheat by coordinating movement speed with the monkey bars. Is there a way to lock a single hand in space so that I can animate the character pivoting on their wrist? Another example for context is a character running into a post/pole, grabbing it with a hand, then running around it in circles with the post/pole acting as a pivot. I would still need to somehow lock the hand (relatively) in 3d space. Thanks for any help!