Why do my torrents upload so slowly?

[Ironic Namesake]

I have a 10mb up / 10mb down line - when downloading at eg. 500kb/s, I'm also uploading at around the same rate or faster.

But for some reason, when not downloading my uploads are really slow like 5-10kb/s , what could be the reason for this?

Here's connection test on speedtest.net :

 

[copycatuk]

Sure you have opened the appropriate ports for your torrent program?