I have now discovered the elliptical at my local gym - and have tried it out a couple of times as well as continuing with the recumbent bicycle ( as well as using the weight machines) . When I run I don't have to make much effort at all to get my HR up to 120BPM - but on the recumbent bicycle I have to push quite hard to get it up there and almost as bad on the elliptical. Anyway, today I did 40 minutes of steady cardio on these two machines ( at 120 BPM) and it was quite a workout for me and I found muscles that I haven't previously used when running. . It is of course completely different to running - but I should be able to at least keep the heart pump fit while I am waiting for my foot to repair itself.