A lot of songs I play have ostinatos with riffs over large intervals and include a changing a middle note.
The treble clef in the image below is a good example.
I have been trying to play this with my fingers 1 and 5 spanning the b octave, and just switching my index and middle finger notes.
When playing intervals like this (which, without a middle note would be close to the maximum interval I can easily reach), through a combination of finger movement and wrist rotation, sometimes my forearm gets tired (in a workout way, not in a painful way).
I am fine practicing these until my forearm is strong enough and my arm comfortable with the interval but I am curious, what is the ideal technique from a physical standpoint to play large repeating intervals? I think this is called "extended position".
Should I try to use fingers only? Should I try to use mostly my wrist with rotation, or something else?