rocky tread

I dreamt that I was getting on to a treadmill, but it was quite large. It was about the width of a lane of traffic and tilted up into darkness. Basically a small structure was built around it and you couldn't see the ceiling of it or the end of the treadmill... or what was coming next. When it was on, it started out like a normal treadmill, smooth black that you walk or jog on. Then a gray cube was on one side, then another on the left, spaced out and easily avoided, but as it went, the tread became more of an obstacle course and you had to jump, leap and climb around the objects coming towards you. I was worried that if I fell, I would get scraped up, but I found that the "rocks" were a dark charcoal foam that although sturdy, had some give. I was moving along doing well, then two guys from high school were behind me. They were very athletic and very tall. At first I was concerned, but they were both there to guide me and help me improve my agility and strength. It was enjoyable and I was looking forward to what might be next.