I don't think you would be able to do any where near that intense of cardio or length of cardio....
you only chance would be if you did the cardio first thing in the morning before you took clen

.....if you take clen before you run like that...good luck

I don't think yoiu would have a heart attack or anything, but me personaly found it hard to breath or do cardio like that.....I could only easy cardio like stationary bike or walk on a tread mill.....these types of cardio burn fat better any way and don't burn muscle...that's what most body builders do.....that's why they take clen in the first place....so they don't need to do crazy cardio when cutting before a competion!
But if you love to run like I do....ECA stack is awesome....it still turns up you matabolism a little, but you can run like a beast

....especialy to a fast paced rap song....like outcast's "B.O.B." (Bombs over Bagdad)
So it evens out....ECA stack is weaker than clen, but you can do long duration and intense carido like running.......however...
if you are a competitive body builder you would lose to much muscle probably, but for the average joe looking to just matain a decent physique it shouldn't be a problem. Plus I feel great mentaly when I run!
I never tried t3, but I'm interested at weather you can run or do intense carion on t3 alone? anyone ever tried t3 without clen and could you do cario?