Pulse rates
Your estamated max heart rate would be 220-age. So for you it would be 196 this could me more or less depending on different factors. The only way to completely find out your max heart rate would be to due a max test with a trained person. You want to get year heart rate up close to this number about 70-80% of your estamated max heart rate will set you working at a difficutl level to maintain for a long period of time. 60-70% will be more sustainable for a longer period of time. If you run for distance you want to be able to hold a conversation with out gasping for breath after each word. Make sure you mix up your HIIT with slower days to provide your body time to recover.