At 12 mph, this constant speed of the treadmill becomes more pronounced since stride length must go up a lot more to sustain this speed
As speed increases also remember that stride rate increases as well. You won’t necessarily get more flight time.
Stride length will increase more but stride rate will go up as velocity increases
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?