I worked on speed and incline (at different times- no I did not run fast hills or anything crazy like that) and feel like I got a great workout. Another day's workout will be running for 30 minutes straight. Today was about BRINGING IT... and then taking a walk break... and then BRINGING IT!!!!...
Here's what I did:
Walk 5 minutes to warm up
6 cycles of the following:
1 minute of running flat at 5.5 pace
90 seconds of running at 2.5/3 incline at 5.5 pace
90 seconds of running flat at 7.1 pace
1 minute walk to recover
Then I walked 5 minutes to cool down.
I think if I do this workout once a week, I'll definitely see some improvement. Plus, it was different enough from a track workout that I feel like I could even run 30 minutes on the track tomorrow and not feel like I did the same workout...
The treadmill finally has a place in my life... thanks everyone for the suggestions!