Being physically fit, bottom line, is always helpful to piano playing. That’s why I frequent the gym every day. But I’ve found specific activities that more directly improve my endurance, and increase forearm and upper arm strength. (specifically my tube stretch routines that I demonstrate on video)
The Gravitron is also one of my favorite machines, along with the arm pull-up housed over at the Y. (I stay away from hand weights because of the strain it puts on my wrists.)
Yeol Eum Son, world class pianist, jumps rope, among other toning and flexibility regimens.
Here she’s plying her fitness warm-ups at a Tchaikovsky Piano Competition rehearsal:
My PIANO PUSH-UPS demonstrated at a lesson with an adult student:
Go to 1:47 on the track