system
Given the following post, respond as if you're commenting on Reddit:
human
Are all muscles contracting? As in there are no "push" type muscles?

What about other species besides humans? And what are non-contracting (I'm assuming stationary) muscles generally used for?
gpt
Yes, muscles can only ever contract themselves. Muscles can only be stretched with another muscle, a "stretcher". You will always have muscles working either way on most of the body's joints. The fingers are a bit different.