Repetitive movements of tiny muscles that were never designed to do that kind of movements in the last millions of years of evolution and suddenly have to handl

Repetitive movements of tiny muscles that were never designed to do that kind of movements in the last millions of years of evolution and suddenly have to handle it hours per day. That can be applied the same to pretty much every modern physical problem (diet, sitting all day, bad posture, carpal tunnel syndrome, &c.)