danny elfboy,
Interresting post, I understand your point about that it's necessary to rest. However, how to have rests in a piece like op 10 no 2 I don't know - you are after all using the same fingers from the beginning to the end, almost entirely without interruptions. Could you explain further please?
Contraction not much a physical process than it is neurological process
Contractile disfunctions are after all under what is known and neurological syndromes
So what I'm saying is that contraction and resetting doesn't start within the muscle itself physically but as neurological stimulus that are uptaken by receptors of movements
This is the real problem. How do you reset if you don't have time to reset?
The answer is that reset and contraction must be as quick as possible and I'm talking about 1/10 of a second. This is possible because neurological stimulus including contractile ones travel at a speed which is way faster than that. Speed again is the delay between contrations and resettings
Think about the singing analogy. Catching your breath is necessary hence you can't wait for a long note or a rest to catch your breath. Simple it occurs so precisely and fast that it occurs periodically without "breaking" the flow of the music
Catching your breath involves both neurological stimulus from the motor cortex of your brain and contraction of abdominal and thoracic muscles to physical opening of vocal folds, vocal tract and larynx
It is hovewer more easy to break the flow of music by catching your new breath than by resetting piano playing muscles. If we active your kinestethic sense we realize that both process are very compelling
Anyway to directly answer your question:
Resetting and contractions are both very fast
Contraction after the notes have been depressed is just a waste of energy
So resetting occurs (like catch breathing) after a certain amount of notes before the hand/wrist lift (more or less) to play a new set of notes
If you practice your whole pieces or long fractions of the piece trying to insert timed contraction and resetting here and there you'll break the flow of music.
That's because your neurological pathway are not yet stimulated by this piece and muscle memory to react so fast
The only solution is to practice a fraction of the piece and
as soon as the compelling need to re-catch your breath/resetting appears you stop, relax completely, take a deep breath, think of the next fraction of the piece and after 30 seconds to 1 minutes play the next fraction till again
the compelling need to reset is felt and you stop again
So let's say your "breathing" forced your to play 1 bar and stop, when all the bars are mastered enough you practice 1 + 2 and stop, 2 + 3 and stop, 3 + 4 and stop
What you will notice is that
althought the physical long rest is not there anymore they are still underlying your playing (i.e. the resetting and contraction is almost subconscious and so fast to be invisible)
When this is achieved you practice: (1 + 2) + (3 + 4), (4 + 5) + (6 + 7), (7 +

+ (9 + 10) and so on. Again you'll notice the same. Althought the physical rest and time to stop for 30 seconds is not there anymore it is underlying your playing, it is still there but so fast not to require any concrete 30 to 1 minute rest
After that you'll practice: (1 + 2 + 3 + 4) + (5 + 6 + 7 +

and so on
Again no rest but neurological fast imputs of contraction and resetting are still there occurring fast and naturally
After than you practice: (1 + 2 + 3 + 4 + 5 + 6 + 7 +

+ (9 + 10 + 11 + 12 + 13 + 14 + 15 + 16) and so on
Takes your time to learn the fraction of piece properly
In other words never move to the next stage if you haven't mastered fully the previous one
You'll notice therefore that the most tedious work is at the beginning when you're learning the piece from scratch, memory is still weak and your fragments are very short
But the system is pyramidal, the more you move up the smaller is the area to cover till you reach 1 or the whole piece
Another thing that works for me is to play the small fragment FAST FIRST
Since we're talking of contraction and neurology it bears saying that starting slow and increasing the speed with a metronome is not effective. It is not effective for occurate speed playing and it is not effective for avoiding tension. The coordination necessary to play slow speed (more delay between notes) and the note necessary to play at performance speed (less delay between notes) is incredibly different
I say practice the smallest fractions at full speed so that you're practicing the coordination that will effectively use at performance speed without the coordination for slow speed confusing you at the beginning. As the pyramid moves up and your fractions are bigger and there's already a contractin/resetting flow implied in your playing you can use the same coordination your use at full speed but with a bigger delay betwee notes (slow motion)
This wil allow you to play slow without breaking or confusing the actual coordination necessary to play fast. Slow motion practice is necessary to focus on certain aspect that are not easy to focus on at full speed: pedalling, dynamics, interpretation, touch
At this point you can use several methods to better ingrain your piece like repeated group or dotted notes and so on
You can always PM me or we can meet in the chat if you have specific questions