Glutes and hamstrings?
 

What sensations tell you if you're using your glutes and hamstrings while pedalling? Or does one always use them as long as one is leaning froward at the hips?

I can feel my quads working - they can burn during heavy uphill exertion.. I just can't figure out what signals use of glutes and hams.

Thanks.

Ed Sassler, Awesome Guy
 

It's hard to explain the sensation and how you sit over the pedals has much to do with it.
I want to pass along this video from Ed Sassler, check it out at 2:00 minutes in and he explains it better than I ever could.
He is pretty sharp, you can find him on the Paceline Forum under the name Ti Design.
Here is his video, watch it all when you have time, catch it at two minutes in for your answer:
https://www.youtube.com/watch?v=tVlcjl05epA

It'll take me time to understand it, and I'll need to get my bike on my trainer, but I think you gave me the answer. Thanks very much.