My exercise routine is 2.75 miles on the treadmill which takes 51 to 52 minutes. I wear a heart rate monitor and set the incline to maintain 115 to 120 BPM. At my age, that equates to 75-80% of max, well into cardio...definitely burning glycogen. I have been doing this for several months and have no adverse side effects.
I am in my mid-50s but I can get my heart rate up to 170 BPM, which supposedly is over 100% of my max, LOL! So I don’t know if that formula is quite correct.