BCAAs are fine during cardio in general, but the idea behind low intensity fasted cardio is the lack of insulin allows you to use fat as the primary fuel source. BCAAs are hyper insulinogenic (produce a lot of insulin), kind of defeating the purpose of doing cardio fasted, on paper anyway. I dont know what people are experiencing in real life. IMO do fasted cardio fasted, if you want to get some carbs and aminos in beforehand go high intensity.
Maybe I will stick with BCAA powder and start having a piece of fruit before morning cardio because I can't go low intensity for the life of me when doing cardio. It's like being behind the whell of an F50 and not getting out of 1st gear, not happening. Im hurtin a little today went into my gym and did crazy cardio on empty stomach well except my Var, pseudo and black coffee. I biked for 20 treadmill 20 then dont know what hit me but started Box hopping and boxer type moving. Then got a rush of pain in my neck which isn't to bad and stopped.
When you say mild cardio you thinking like 65rpm?