Chopin's Octave Etude

     Sometime ago I posted a YouTube video

Chopin

demonstration of octave playing in Chopin's octave etude. (You can view it HERE.) My point was that fingering octaves using fourth finger on black keys does not make the octaves faster or more legato and the potential for injury is considerable. 
     I received the following two comments:
     "What is wrong with chromatic octave fingerings? My teacher and many pianists use the 4th finger on black keys and 5th on white keys. Is it only bad for small hands? I am confused because all other sources told me to use the latter fingering when playing this piece."
      "I agree that fingering octaves doesn't necessarily make them faster or more legato, but it comes down to the pianist's hands. Some people might find using 4 on black keys more comfortable since there's less movement. With smaller hands this might be uncomfortable but I don't agree with telling everyone to always use 5 just because it's better suited for your hands."

     My use of all fives has nothing to do with the size of the hand. Practicing octaves repeatedly, enough to make virtuoso octave passages secure, the potential for injury is considerable when stretching—1-4 or 1-3 (yikes)—even in a large hand. FYI, moving is more efficient than

Muscles Pulled Against
One Another

stretching. When stretching, muscles tend to work against each other, hence the feeling of tightness pianists often feel when playing these passages. Forearm rotation alleviates this problem. I play consecutive chromatic octaves in line with the black keys and hinged at the fifth finger. The rotation is so slight as to be virtually invisible (something Matthay described at the turn of the last century). 
     Since you agree that nothing is to be gained by fingering octaves, why not explore using the hand the way it was designed to be used? Look up Gary Graffman and Leon Fleisher, the latter of whom developed focal dystonia, a condition ​caused by muscle stress and overuse. Try this: First play a black key octave with 1-4 (or even 1-3). Then, play that octave with 1-5 and ask yourself which feels smaller.