Muscle Use

When sitting at your desk only use as much muscle power as is required.
Example :
You can thump the keys down heavily when typing (lots of effort), or you can gently tap the keys (little effort).
Shoulders can be hunched up (lots of effort) or relaxed (little effort).
Head can be leaning forward (lots of effort) or relaxed and straight (little effort).

Using more effort than necessary may make discomfort, pain or injury happen more quickly than if you use your muscles efficiently and relaxed.