Ive been doing a lot of reading on HIIT and havent found a clear answer. Some say HIIT is all you need, others say they do both. Can I replace my cardio with HIIT instead? I generally do 30 minutes at about 70%. I did my first HIIT today and man I felt funny afterwards. My legs almost gave out and I was actually winded for a while, which has happened in a few weeks. I am looking just to burn excess fat. I want the muscles, I dont think Ill ever be really skinny( I have a natural big build) and I was just wondering if I am wasting my time doing the 30 minutes of treadmill at 6 mph.