As I learn more Bach on the erhu, swimming always helps me. I’m just learning to internalize putting my clasped fingers into the water more horizontally, beginning the back-pull more immediately and maintaining the power.
When I get home, I take up the erhu, calibrating my motor-movements—string crossings, changing positions, breathing—in the service of my sound-ideal. Still sounds a bit rubbish, but hey. Practice makes perfect.