btw i didn't get tendinitis from playing piano.. from physical activity like working out
it's all connected
tendonitis is caused (except on pregnancy) by accumulation of muscle tension
so if you tend to accumulate tension you do it in whatever acticity
even writing with a pen can trigger tendonitis if there's accumulation of muscle tension
even lifting weight, playing tennis or gymanstic ... even if none of these activities is supposed to cause tendonitis
Tendonitis is not "natural" and getting it is never a matter of fate or cruel destiny, it is always caused by wrong our own wrong body use.
Getting tendonitis from whatever activity is a sign that one must reconsider efficient body use at the piano too