I dunno about that. I recently ran two 5k legs of a duathlon (my wife did the cycling) and completed each leg in about 22ish mins, all without any run training and I frankly hadn't run a 5k since 2009 (and my time then was 35:10) and was fat and out of shape until I started cycling in late 2013. Yes, I was sore for a few days from using muscles I don't cycling, but my performance is solely attributed to cycling fitness. However, I will grant that I probably won't be able to improve my time without some run specific training (which I am unwilling to do lol)