How to check Resque worker status to determine whether it's dead or stale

The default resque web interface says that I have 5 of 7 workers working. I don't understand how this could be happening.

I'm on heroku, so when my dyno restarts, it should spin down existing dynos and workers, then spin up a new one. So, I'm assuming some of these workers are stale, but resque thinks there are so many more workers working than there should be... (there should only be 1)

How can I check whether any of these are stale or dead? I expect to see only 1 worker working.

Eventually, I expect I'll do whatever this SO post says: How do I clear stuck/stale Resque workers?, but first I'd like to know how to determine whether a worker should be removed...

Apologies if this is an obvious question. I'm new to resque.

Thanks!