past his prime wrote:
I'm not sure how well hill reps and a treadmill would replace hill reps on a hill, but you should consider a couple factors first. One, a lot of treadmills won't go as fast as you should be going for hill reps. Two, what you describe is very hard on treadmills. If you're doing this on your own treadmill, hopefully you have a service plan. If you're doing it on someone else's treadmill, don't be surprised if they ask you to leave.
Steep inclines are actually easy on treadmills, gravity is doing most of the work so it lessens the strain on the motor. A negative incline would be really stressful though, because the treadmill would have to pull your weight uphill- which is why few treadmills have this feature.
Some treadmills even come with a baked-in 1% or 2% incline, even when they read 0%, to lengthen motor life and simulate the effect of air resistance.
One downside of outside hill repeats is that the rest periods are too long, so treadmills at least don't have this problem. I think the main issue would be how fast your treadmill can ramp up speed and incline.