2 recent studies (2nd one is linked in the first) demonstrating that interval training may be superior in terms of post-exercise burn...
Personally, I'm a big fan of 60 minute cardio sessions, but reading these studies that me thinking about finishing them off with 1-2 interval sprints... http://sweatscience.runnersworld.com/2012/10/post-exercise-calorie-burn-after-intense-intervals/Post-Exercise Calorie Burn After Intense Intervals
October 16, 2012 12:00 am
At the Integrative Biology of Exercise conference in Colorado last week, researchers from Colorado State presented some interesting new data on the perennially controversial topic of post-exercise calorie burn (see press release here). They locked volunteers in a metabolic chamber for two 24-hour periods; during one of the days, they did a high-intensity interval workout on a stationary bike: 5 x 30 seconds all out, with 4:00 recovery (easy pedaling with negligible resistance) between each sprint. The result: they burned an extra 200 calories over the course of the day, not including the calories burned during the workout itself.
As it happens, that's almost identical to the result produced by researchers at Appalachian State in a similar experiment, where the exercise session was 45 minutes at 70% of VO2max. In that case, the subjects burned an extra 190 calories during the day following the workout. So there are various ways we can interpret these results:
Interval training and sustained endurance training produce essentially the same post-workout calorie burn, so there's no difference between them.
Interval training is far superior, because you can stimulate the same calorie burn with (as the press release puts it) "as little as 2.5 minutes of concentrated effort a day." Even if you choose not to be grossly misleading by not counting the recovery time between intervals, the interval workout still takes less than 20 minutes, which is much less than 45 minutes.
Sustained endurance training is far superior, because you can stimulate the same calorie burn without enduring the intense discomfort involved in all-out interval training. (And believe me, if you've never done repeated Wingate tests -- the 30-second maximal cycling sprints used in this study -- they really are painful!)
As always, the truth probably lies somewhere between the various options. Overall, the similar results in the two studies add to the large pile of evidence that high-intensity interval training offers many of the same benefits as sustained endurance training -- the trade-off is that you have to exert greater effort, but for a shorter time.
If you're trying to decide which is better, my advice is: don't. A head-to-head comparison of the two approaches a couple of years ago found that, as expected, many of the gains (e.g. in parameters like VO2max) were the same. But the gains were achieved in different ways: interval training produced more gains in the periphery (e.g. muscle) while endurance training produced more central gains (e.g. heart). Why stick to just one approach when a mix of both is probably better?