kmurdick wrote: ↑
Fri Jul 21, 2017 8:59 pm
Just to add a bit to my last post. The argument against the the natural return is that it wouldn't return fast enough if you had to depend on ambient tension to do all the extending.
Well that was one point against, but I seem to remember others - two of them were that it wouldn't go far enough, and that it isn't very plausible that a body provided with pairs of opposing muscles should rely on one side to do all the work and use the other side as an elastic band.
I would have thought the way to get the fastest return might be to pre-tension the flexor, in which case you would effectively be pushing against a fatter elastic band, making the extension of the MCP harder and slower going, but you'd get a faster rebound. This would mean giving a much bigger share of the work to a very small muscle, which strikes me as implausible. It might give you a faster rebound, but this would come at the cost of a slower plant and I doubt the stroke would be faster overall. Anyway, we will never find out whether this is going on by introspection or by looking at videos - we would need to monitor the muscles themselves.
But maybe it would if the two main joints were timed differently. The knuckle joint begins it extension before the middle joint finishes its flexion, and then the knuckle joint starts it flexion before the middle joint finishes its extension. Remember, it is not incumbent on either joint to complete its full natural extension before beginning its flexion, you can cut that extension off without causing undo tension. This might be what allows it to go so fast.
I don't understand this point. The first bit sounds plausible to me - the return may well be faster if the MCP begins to extend before the PIP has finished flexing. I can't make any sense of the second bit though - you are saying that this timing is only possible if the extension of the MCP is due to a passive rebound rather than an active contraction? Why should that be?
Edit: I said "pre-tension the extensor" when I meant the flexor.