Holy crap, did I go down the rabbit hole on this one.
SuperAthlete J, the one and only reader of my blog, wrote to me after my post-a-palooza yesterday and said she was particularly interested in what I'd written about a study saying cardio intervals offered more fat-burning potential than regular old steady state cardio.
I've seen and heard a lot about this idea for the past several months -- it does seem like the fitness industry has bought off on it hook, line and sinker. But, as I flipped through my magazines to refresh my memory and compose this post, I realized that no one is actually quoting the source material. I can't seem to find the original study. Instead, after a long Google session, all I found was a lot of questions, counter-claims and argument. Hmm.
Here is what I can say: generally speaking, it looks like cardio intervals can help burn more fat than steady-state cardio. And here is why (this is the tricky part):
• Apparently, intervals can generate a higher EPOC than steady-state cardio. What is EPOC, you ask? (See why I ran around in circles on Google?) It stands for Excess Post-Exercise Oxygen Consumption. Higher oxygen consumption means more calories burned AFTER THE WORKOUT IS OVER -- the mystical "after-burn" of exercise. Which means you not only benefit from the workout while it's happening, but for a while afterward as well. One article I read quoted an EPOC rate of 14% for intervals; 7% for steady-state. I don't know what those percentages correlate to, but even a science dumbass like me can see that intervals create twice the good thing that steady-state cardio does.
• There's also some research showing that HIIT (another acronym, another Google search!), which stands for High Intensity Interval Training, can help suppress appetite after a workout, thus leading to fewer calories consumed and more fat loss. Not sure if that's true for me and it doesn't really speak to the benefits of interval training as opposed to a side effect, but OK.
• Then there's research showing that because intervals mix things up during a workout, people find them less boring and stick with them ... which is another way of saying that doing anything at all is better than doing nothing. I definitely don't know if that's true in my case. I used to dread interval days and look forward to relatively mellow steady-state days where I could just hop on the stairclimber or elliptical trainer and read my book or watch TV. Intervals require a lot more attention and effort; sometimes I just want to zone out.
• It is also thought that intervals lead to decreased muscle catabolism (another Google search!), or degradation of the muscle as the workout progresses. I can't really comment any further on this one because I honestly don't fully get it. Don't we want the muscle to degrade so it can build itself back up? Maybe too much of that is a bad thing and intervals strike a better balance? I'm not sure.
The problem, in my mind, comes when people make claims saying that it's possible to get just as much gain from a 20-minute interval session as they do from a 60-minute steady state session. Unless your steady state is extremely moderate, that's not going to pencil out in terms of calories burned. Even when you add in the increased afterburn rate related to intervals, intervals probably lose.
Here's what I think: just like everything else related to diet and exercise, there's no magic bullet or quick fix. You've got to put in the time and effort. I just can't buy off on the idea that I can get just as much benefit (read: burn the same amount of calories and fat) in 20 minutes of hard work as I can in 60 minutes of moderate work. Maybe that's the skeptic in me. Maybe it really is possible.
But I don't believe it. So, despite the many asides in the fitness magazine articles touting the benefits of intervals -- and how they can reduce my overall workout time -- I'm not drinking the KoolAid. However, I am sipping it.
I really do believe in the power of intervals -- as an element of an overall exercise plan. And what I emphatically DON'T believe is that I can get away with substantially reducing my exercise time when I incorporate intervals into my workout. I could be wrong, but it just feels too risky.
So, what I've been doing is this: I make sure that I achieve a range of heart rates in all my cardio workouts. I want to cover everything from moderate to balls-out, and spend a pretty decent chunk of time at the latter end. To make that happen, I'm doing more classes -- spinning and Zumba in particular feel good because they alternate between moderate and high intensity work. And on my "machine days" at the gym, much as I'd like to, I don't set the elliptical to Level 10 and leave it there for an hour anymore. Instead, I work out at a moderate/high rate for 20 minutes. Then I do ten intervals: one minute at the highest intensity I can muster, one minute of recovery. That's another 20 minutes. Then I wrap up with a final 20 minutes, going back to the previous moderate/high rate. (Of course, all of this would be a lot easier if I was able to run, which offers the simplest opportunity to build intervals into a workout.)
In my mind, my approach gives me the best of both worlds -- the benefits of interval training and enough duration to really burn some fat and calories. God knows I couldn't manage 60 minutes of intervals, which would probably be the optimum (and superhuman, as far as I'm concerned) way to go.
I really don't know my way is the right way, but it's feeling good so far. I definitely know that I feel more wrung out after a session involving intervals than I used to after a steady-state workout. And my pants are fitting, even though I can't seem to stay away from the bag of fun-size Big Hunks I bought at the drugstore.
I'm going to close with a link to a page that represents the extreme end of the current rage for interval training -- this one says you can turn your body into a "fat-burning machine" in just 8 minutes every 3 days by following the "Tabata protocol." To me, this is the equivalent of those ads that say "Eat what you want and still lose weight!" Too good to be true. Maybe it works ... but I'd be too scared of busting out of my pants to find out.