This song is one of the musical centerpieces of “Rocky IV”, full of life and hope, but at the same time it's not that popular as some other songs from this soundtrack. Oh well, we have no reason to ignore it, especially since it's one of those good-spirit 80's classics you can sporadically hear on the radio and it has even peaked at number 76 on the Billboard Hot 100 chart.
Anyway I'd like to say it's not really the original bass line what I played here. First of all, the original one had some slap elements and I don't play slap (sorry, I just don't like it and have no wish to learn playing it). And secondly, I didn't find any correct tab for “Heart's On Fire” online (I found some, but they were not even close) and had to give some work to my ears :) My part sounds sort of ok I guess but I can't guarantee this is exactly what they had on the record. Take it as “what if someone played it with a pick” version :)