The quality of the tone
No matter, what instrument you play - or if you sing - as a Musician you are aware of the quality of your tone. Of course, there are many factors that influence this quality. One of them is a very basic one: Your body. The more ease you have in the use of your body, the fuller and richer your tone becomes.
Injuries: yes indeed!
As performing artist you use parts of your body repetitively over long periods. That makes it very important to know HOW to use your body in the most natural and coordinated way. You need to know how to play with (and not against) your body!
Unfortunately there is an extremly high percentage of performing artists that injure themselves as they are not educated in how to play without putting too much strain on their bodies. Let me give you a quote of an atricle called "Cumulative Trauma Disorders In Musicians" by Kee Fedak, DC:
"Until recently very few studies or surveys were performed to elucidate the widespread nature of injuries associated with musicians...