"I just can't seem to get my fingers to move! I can do all my scales up to tempo, but not arpeggios..."
Once you have a problem with arpeggios, you might have many other problems, and even of such kind, you probably have no image of their existence yet...
Trying to solve your troubles, firstly, I would like to suggest checking up the dynamic level you are practicing your "terrible" arpeggios in. Many troubles would appear due to unnecessarily loud playing. As singers do (they, who knows what the real "bel canto" means...!) - maybe - you should start your arpeggios with about "mezzo piano" sound, looking for extremely smooth & fluent getting of the next & next sounds - without any strokes and strikes. The real fluency cannot be reached if one practices the technique using such training methods that, factually, persistently damage it! Such activity might be compared to cleaning of the home just by scattering garbage around...
So - the dynamic level of your PRACTICING has to be checked up at first.
The next problem, possibly, could be more complicated: I would like suggesting determine the boundaries of using the really physical power in producing of a sound. In my opinion, you might get much better results trying to use such elements as even "the weight of your fingers", playing such innocent technical figures as simple arpeggios. In any case nobody has to use the simple muscles' power when realizing such plain tasks!
You have to take into consideration - what will happen if you start to play the "Feux follets" of Liszt, Schumann's or Prokofiev's "Toccata", "Etudes tableaux" of Rachmaninoff, etc - if even simple arpeggios are bringing about greater instrumental problems?
Once again: the "mezzo piano" dynamic level at start, the smoothness in articulation of the each one sound, the possibly high level of mechanic easiness in hands (not too much raw muscles' power). Instead of accents that disturb the musical line, one should try to achieve some kind of virtual motion of musical energy inside the vision of each one sound. In such situation "to connect" alive and artistically valuable sound to another one will produce not so many troubles as connecting the motionless, artistically empty sound to the next one of the similar kind...
The very important aspect of the problem, maybe, is the artistic emptiness of practicing: as I am nearly sure, this is the main source of many instrumental problems, because the human being (especially if talented!) does not like to fulfill his/her life by just the fingers’ training...!
According to highly interesting and remarkably rational the Abby Whiteside's remarks - a CENTER must direct our work, not a PERIPHERY (so - imagination and intelligence, not muscles)! Therefore one should firstly try to create the proper image of the sound and after start to practice so, that some kind of artistically worthy background - an emotion, a color and a virtual motion inside of vivid vision of each one sound - will enrich that formerly empty arpeggio...
The next thing, that - nota bene - is strongly connected to former questions, I would like to define as the helping effect of the "virtual bow" that has to be build in our hands. It will steer their actual (for surface - purely physical) action and make the fingers work more comfortable; though, however the fingers are of extremely importance in playing, they still cannot manage all the things in the piano technique!
Here has to be found the proper division of duties in playing the piano. Let you see:
- the fantasy must produce the artistic image of the form,
- the ears must control the accuracy of dynamic levels that decides the technical economy of playing - generally,
- the fingers have to activate the hands’ action,
- the virtual bow has to integrate all the physical parts of the instrumental work.
Because The Artistic Goal must determine the technical means, therefore it is fully impossible to achieve the mastery in piano technique without serious participation of such fundamental artistic factors there - as imagination and creative fantasy, and as well without greater controlling support of our sound detectors, ergo - well-trained ears.