Fantastic, I love quick simple sketches like this one, they have so much life in them
It is never easy to capture something of a genuine, natural movement (life) in a piece of art. Making quick sketches is a good practice for achieving that aim.
....Where you say `quick`...I say dynamic...!!
That's right, Mark, that's the whole point...When properly done, quick/expressive sketch = dynamic, lively! In fact, they are the synonyms :-)