It seems to me the experts used to say you need to do at least 20 minutes of cardio at least 3 days a week in order to improve your stamina. But if you Google it now, you get lots of different answers. Some say 30 minutes/3 days a week, others say 20 minutes/5 days, 30 minutes/5-6 days, first 20 minutes only burns glucose, etc. And they all claim to be quoting some authoritative study of some type.
Any opinions or does anyone have a good reliable source for info on this?