this is how I started in 2007
Cool Running | The Couch-to-5K ® Running Plan
I started in the Spring. In the beginning I could hardly do quarter of a mile without having to decrease my speed and walk. I alternated between running and fast walking for months, with my running intervals getting longer and longer each time. Now I can do 4 miles without stopping at moderate speed and a small grade incline, something that seemed beyond my reach several months ago.
Now, whether running is the best exercise for your body (chronic cardio), or whether is Primal, I don't know. I'm kindof addicted to it now and it seems to work well for me.
I wouldn't say that running 3 to 5 miles several days a week is considered chronic cardio.
maybe it's because I'm not a runner, but RUNNING 3-5 miles SEVERAL times a week (which is what you originally said - the word "several" implies more than 4) sounds like chronic cardio.
JOGGING 3-5mi three times a week does not necessarily sound like chronic cardio.
does that make sense?
For me running 4 to 4.5 mi. 5 days a week doesn't seem like I'm doing any harm to my body (well, except risking an injury, but there is a risk involved with any type of exercise). I don't feel exertion to the point I feel like I'll faint unless I stop right now, on the contrary it's rather effortless. I feel good while running and how could that make my body release cortisol?
So, IMO of a person enjoys a certain type of physical activity and it doesn't feel like it's putting much stress on their body I don't see anything wrong with continuing that activity.