Ever punch a mylar balloon? It makes a satisfying "pop"
sound
unlike rubber balloons. They also don't bounce as far since
the skin isn't under tension like a ball. It's just a bag filled
with helium.
I was thinking this would make them good candidates for
sparring targets. Put a few in the
gym that are filled
enough
to float at
head, chest and stomach height and punch them.
Before you sour on the idea because it would look insane,
which it admittedly would, consider:
They'd move about the ring un-predictably like a human
opponent.
You could punch while advancing on a moving target,
something you can't do with a heavy bag.
You'd be turning and maneuvering constantly just as in a
real
fight.
They'd make that pop sound when you hit them.
If you hit them hard enough, you might even be able to pop
them, thus giving the added bonus of harder punches
being indicated by a popped balloon. One might try to pop
all the balloons in a
certain
amount of time.
Like I said, it would look like you're insane but it would
offer
some things that heavy bag work couldn't offer. It might
also be a lot of fun, like when dogs chase soap bubbles.