Questions about muscle physiology and metrics to quantify the physiological aspects are on-topic. However, your question itself is quite poorly worded and contains no explanation whatsoever.
I wonder what metric is used when quantifying muscle tightness.
There are possibly several methods to test muscle tightness. It is generally expected from the OP that they put some effort in their questions. There are two reasons for this:
- It reduces unnecessary burden on others to do the basic background work (i.e. the 'homework'). Moreover, since you have asked the question it is a general etiquette that you provide all necessary explanation instead of outrightly demanding an answer from the others.
- It provides a context to the question and the details would make the question more specific. This reduces the effort of the answerer, attracts higher quality answers and also conforms to the SE policy of keeping the answers crisp, terse and to-the-point.
Downvotes in the main site indicates that the voter thinks that the question is not useful or is of low quality. The tooltip says:
This question does not show any research effort; it is unclear or not useful.
So, even on-topic questions can be downvoted if they lack quality.
In meta (especially discussions), downvote can also indicate a disagreement.