You've probably heard that interval cardio is better than steady-state aerobic exercise for burning fat. You've also probably heard that doing 20-30 minutes of medium-intensity cardio after a weight workout is a great way for burning fat. So which is it?
To start with the basics, interval cardio is when you go all out for 30 seconds of an activity like sprinting, alternated with slower, steady-state work for one minute like walking between sprint sessions. This method of cardio has been shown in research studies to burn more fat after you're done than medium-intensity steady-state work.
Why? Because of muscle damage. Sprinting or pedaling on a bike all out for 30 seconds calls on more fast-twitch muscle fibers, similar to a weight workout, and that causes muscle damage. The repair process from that boosts your metabolism and therefore means you're burning fat more efficiently because fat is used as an energy source during the muscle-repair process.
When you get down to it, if you're putting in 100% effort as you should, then interval cardio is similar to an intense leg workout. Since that's the case, you should avoid interval cardio on the day before or after a heavy leg workout. On the other hand, you could use it as one of your weekly leg workouts or in conjunction with a leg workout if you reduce the volume so you can end your weight-training session with interval work on a treadmill or stationary bike.
As effective as interval cardio is, the main issue to watch for is overtraining if you use it in place of your steady-state cardio. It does take more planning to implement it correctly because of the muscle damage since you're essentially adding another high-intensity workout, but that planning can be well worth the effort.
If your quest for burning fat is because you've got a lot to lose, then 20-30 minutes of steady-state cardio at the end of upper-body workouts is a fine idea. After weight training, all of the sugar is out of your bloodstream, so your body ready for burning fat as its fuel source.
Interval cardio can be extremely effective because of its extended efficiency, so if you plan to use it, be sure to use the above recommendations, doing it either as part of your leg workout or as a separate leg workout. And if you're doing your cardio first thing in the morning on an empty stomach, the muscle-preserving and energy-boosting effects from BCAA Boosted will go a long way to helping you reach your goals.