Suggestions for low impact but high cardio exercises/sports?

[almarama]

I have been a runner for a few years now. I've finally messed up my leg enough that I've been told to stay off running indefinitely!!! This of course is a tragedy for me. I would like to find a sport that is low impact but has the same 'high' and gets the heartrate as high as it would have when running. I'm finding it difficult training on Cross Trainers, Elliptical Machines, etc... I feel my movements are SO restricted and for that I feel chlaustraphobic on them. Moreover, my heart rate never goes high enough anyway, which becomes very frustrating. I go spinning twice a week, but I feel I need variety, to compensate the 'loss' of running. Is there anything else out there? Swimming at the moment is not an option for the next 2-3 months (they're doing works on the local pool here, and therefore it's closed). Are there any sports out there that I haven't heard of perhaps?! Your advice and help is very much appreciated.