Photo: pasukaru76/Flickr

"Can You Get Fit in Six Minutes a Week?" asks the New York Times Well blog. Wishful thinking. If six minutes a week is all it took, America wouldn't have a fitness problem.

But when researchers used rats to create two very different exercise scenarios, the results really were very interesting. One group was made to swim for six hours -- two sessions of three hours each. The other group swam in short, fast bursts of extreme intensity -- 20 seconds at a time -- for a total of four and a half minutes. What they found was that the muscles of both sets of rats had undergone molecular changes that indicated increased endurance.

It's called interval training. We've talked about it here before at That's Fit, about how it can increase fat loss, work your heart and lungs, shorten your workout time and suppress your appetite. Sounds perfect, right?

There's always a catch.

While interval training is a fantastic way to blast fat, it's not as simple as speeding up from a walk to a jog every 20 seconds. Efficient intervals -- they have to hurt. In fact, during those sprints, you should be working at 90 percent effort. In other words, according to this perceived exertion scale (which happens to be my favorite), you should be thinking, "I'm probably going to die."

OK, we don't want you to die, of course. But the point is -- and it's one that Well makes, um, well -- not every exercise or exerciser is suited to this kind of workout. Runners, for instance, might find themselves with injuries pounding the pavement. But indoor cycling lends itself well to intervals.

We'd love to hear your experience with intervals. Do you use them regularly? Do you feel like you get fit faster with intervals? And what do you think about the notion that -- done right -- six minutes a week would be enough?