Neat link and ideas, thanks.

I'm still myself a bit leery of sticking 2 x 4's on the back of my treadmill (Sole F80) as I'd be running near the max treadmill speed (def well under 6min/mile) and really taxing the motor. I've done a belt calibration (easy, you just push a few buttons) on it and when it goes faster than 6:30/mile, I get really anxious - and I'm not even on it!

Definitely agree it is a combo of both and not all "additional flight" due to stride length increase. But there is some!

To Lightheir, I don't THINK you need to run at treadmill max speed on the decline because you are really going to tax your motor. Even 8-9mph range at minus 2 to minus 4 is probably fine. This way you can run around the speed of your BQ time with low cardio stress but additional eccentric stress and coming back to what Maurice said, the chance of screwing yourself up is lower at lower speed.....same diff between running downhill outdoors at moderate speed vs high speed. How often do you run at 10 mph downhill outdoors for sustained periods in training?