My main thought is still, "This isn't running", but I think it was good for me, and I did try to focus on those positives.
So I figured I could edge the pulse rate up to the 140 mark, and keep it there without too much pain, and it was enjoyable enough seeing how that went. I'm a bit shocked at how high my recovery phase pulse rate stays. For most of the "walk" it remains close to 140, and falls to a minimum of about 125. That might be a sign that I have a way to go before I'm fully "fit" (whatever that means). It occurred to me that it might be interesting running with a heart monitor (although tracking it might be a bit of a pain, and detract from the sense of flow that sometimes arrives to make it all worthwhile).
In the last run, I bumped it up to 150 (ow), and in the very last 60 seconds I looked anywhere but at the instruments and just pushed up to the gasping level (whatever that may be in beats per minute -- not far North of 150 for this particular flesh machine, I think I glimpsed in a sneak peek).
I might just stick around on Week4 for a while (something I'm very familiar with), because it's actually quite hard to walk when I get off that machine. Poor bum! It's used to nice cushions, not cycle seats.
Oh, and I think my cadence might be all right. I was worried that it was really hard to hit even 100 rpm, when the recommended running cadences I've seen are between 150 and 180 bpm. Then I realised there are 2 "footfalls" per revolution, so you presumably double your rpm to get your equivalent cadence. I hope so! 100 rpm was really difficult to maintain for more than a few seconds, and even 90 is hard to sustain for any length of time.
Provisionally, anyway, it looks like it might be possible to spin (and find ways of actually Wanting to) if running ends up unavailable. Of course on my cool down walk there were runners to envy everywhere.