I've been reading Runner's World and wanted to share this article. I think I'm going to add small sprints to the end of my runs to try to get this effect going and especially to get rid of my abdominal, visceral fat!
Sprinting for Weight Loss: Are Catecholamines the Secret?
Over the past few years, the big buzzword in exercise circles has been "high-intensity interval training" (HIIT, or some variation on that general theme). Study after study has shown that really hammering for short bursts produces the same (and sometimes better) adaptations compared to a typical long, slow "cardio" session. I haven't seen all that much research on HIIT for weight loss, butblogger Rebecca Gardiner pointed me in the direction of an interesting new Australian study (news article here; free full text of the journal article here).
The study itself is encouraging, thought not really earth-shattering. A group of 46 overweight men were assigned either to a control group, or to an exercise program consisting of three 20-minute workouts per week for 12 weeks. The workouts were simple: alternate 8 seconds of sprinting (on an exercise bike) with 12 seconds of easy pedaling, keeping the heart rate in the 80 to 90% of max range. By the end of the program, the participants had dropped 2 kg of fat, and added 0.5 kg of muscle, plus various other positive effects like 17% less visceral fat and improved aerobic fitness. Pretty much what you'd expect, I think.
One thing that caught my attention was the researchers' explanation for why sprinting works better than longer, slower workouts than burn a roughly equivalent number of calories:
Fast sprinting caused the body to release high levels of a specific group of hormones, called catecholamines, which drive the release of fat, especially abdominal and visceral fat, from fat stores so it can be burned by working muscles.''We don't know why, but moving limbs very fast generates high levels of catecholamine,'' Dr Boutcher, whose findings are published in the Journal of Obesity, said.
That's interesting, and new to me. The journal article cites several earlier papers that have documented this effect, so obviously the idea has been out there for a while. I'll be interested to see what other factors affect catecholamine release, and how big a difference these hormones really make.
As for the workout itself, 20 minutes of alternating 8 seconds hard with 12 seconds easy actually sounds pretty challenging -- that's 60 sprints, albeit short ones! The rationale:
Sprinting for eight seconds raised a person's heart rate while keeping lactic acid release, which make muscles tire quicker, to a minimum, he said.
Hmmm, I thought the "lactic acid makes muscles tired" idea was history by now. Oh well. Still, perhaps the idea of an 8-second sprint is less intimidating for people who haven't done high intensity exercise before, akin to the 30-20-10 workout that Amby Burfoot blogged about recently
