Alternative to Road Running

A posterior compartment injury has been keeping me from running for a long time now. Almost two years. Its as frustrating as it gets. But off lately things seem to be going better. Recently I went to this physiotherapist who recommended total no to any kind of impact exercise like running or skipping and start with lower body strength training in the gym. I have been following the program for like three weeks now. Around 40 min to an hour of cardio each day and 4 days of weight training which basically includes 4-5 exercises like squat, lunges, good morning, and back push lunges and calf exercises like neutral, inversion and eversion calf raises.

I tried running a couple of days back and could very easily do around 8k at a decent speed. I recently went through an article on runnersworld.com where an athlete said she hardly does any running practice and improves cardio strength by cycling, cross trainer + weight training for lower body and goes straight for marathons. Interesting.

I have also decided to give it a try. May be after another 2-3 weeks of weight training I will go for a 12k or something like that. I guess it will be great if I can do something like 8 - 12 - 15 - 17 - 21 and wow you have a half marathon. That would involve increasing the cardio workout significantly along with increasing distances.