Before Bfl I usually did 40min cardio with 30min being at 75% max heartrate. 75% max is the highest hr I can get to without causing heart problems. I never really improved my cardio with this workout. Doing the interval of bfl got my heartrate way higher and really irritated my heart condition any though its only for a few minutes. (bad valve which causes something called exercise intolerance).

What is the next best cardio workout for fat burning, I can do lower intervals but do they do any good lower? Or should I do longer cardio. My goals are having good heart condition and fatloss.

I'll appreciate any advise.

Nancy