I was watching an interview with Zhang Jike today,

and he said that table tennis can't be played well at high altitudes,
because the ball speed is too fast there, which makes it very different from coastal cities—almost like two different sports.
This statement surprised me. I grew up in Yunnan for a while when I was a kid.
I felt like I was pretty good at table tennis, but after college and then going abroad, I became much worse.
I always thought it was because I hadn’t played in a long time, but now I wonder if it’s possible that practicing at high altitudes before affected me? Maybe I was getting altitude sickness?