Remember Luca, HIIT is High Intensity Interval Training... Nothing there states you have to run... Do an elliptical at a fast pace for 5 minutes, do push ups or ab work for 5 minutes rest for a few minutes and repeat or something along those lines... You don't necessarily have to run on every hit day... Push ups and sit ups can be part of a HIIT workout as well... Just an option you can look at...