Q: I keep reading that interval cardio is better than steady-state aerobic exercise for fat loss. Should I be doing intervals instead of ending my workouts with 30 minutes of medium-intensity fast walking?
A: Interval cardio, which is going all out for 30 seconds alternated with slower, steady-state work for one minute, has been shown in research studies to burn more fat postexercise than medium-intensity steady-state work. The reason? Muscle damage. Running or pedaling a stationary bike all out for 30 seconds brings in the fast-twitch fibers, just like a weight workout, damaging them. The repair process is what boosts the metabolism and fat loss. It’s been shown that fat is used as an energy source during the muscle-repair process.
In our X-treme Lean e-book we use the example of running on a track for interval cardio—you sprint the straight-aways and walk the curves. As we explain in that e-book (the Q&A section on page 87-88), interval cardio is very similar to an intense leg workout with weights. Because of that, if you choose to use it, you should not use it the day before or after a heavy leg workout. You can, however, use it as one of your weekly leg workouts or in conjunction with a leg workout. For example, you could do your normal leg workout, but reduce the volume so you can end the session with interval work on a treadmill or stationary bike.
The main point about interval cardio is that it can trigger overtraining if you simply use it in place of your steady-state cardio. It takes more thought to implement it correctly because you are damaging muscles—essentially adding another high-intensity workout to the mix.
If you have a lot of fat to lose, steady-state work at the end of most of your upper-body workouts is a good idea—that is the 30 minutes of medium-intensity walking you’re now doing. After weight training, all of the sugar is out of your bloodstream, so your body is primed to burn fat almost as soon as you hit the treadmill.
If you want to do interval cardio, use the above recommendations—as part of your leg workout or as a separate leg workout during the week. It will add up to a faster fat-to-muscle transition rather than no-gaining overtraining.
Till next time, train hard—and smart—for BIG results.
—Steve Holman and Jonathan Lawson