JB3
I have been doing cardio 530am on an empty stomach, and I never get aches, I actually tried drinking a protein shake one morning and I could barely keep my intensity level up, so I went back to an empty stomach, before cardio. I do 1 hour of cardio, using 2-3 different machines, I think this works best for me, I lost a good amount of lbs, and fat with my cardio and weightlifting regimen.
I use the elliptical stair climber 45 mins HR 155,80-85 % I burn 560 cal. I then will jump on the cross trainer, the one with the handles for 15 mins and burn 200 cal. If I ever use the treadmill or stationary bike I can never burn more than 400 cal, and hour. So, if I want to do any running, I'll run on the street for a couple of miles.
I have been doing sprints for years, I sprint for 100 yards, I go for about 90% of my speed, I will do about 10 sets and believe me your muscles will grow and you will be much leaner, I sprint once a week, because I work my quads in the gym on Tue, so I will sprint on Sunday.
you read all the scientific studies and jargons, but your genetics has alot to do with it, you have to go with personal experience not theories.