Case Study: 12/8 Sprints

by Charlotte on November 5, 2007 · 9 comments

My current fitness experiment centers around this research from UNSW in Australia. Nothing like a study from a foreign country to get me all riled up!

The program: 2 sessions per week of 20 minutes on an upright bike. Each 20-minute session is broken into 60 mini-sprints of 8 seconds followed by 12 seconds of recovery.

The claims: Researchers found that, compared to a control group who biked at a moderate intensity for 40 minutes, subjects lost an average of 2.5 Kg of fat. When two outliers with a BMI of less than 20 were removed, the average was 4.5 Kg of fat. The control group gained 0.5 Kg of fat. Researchers also found that in the HIIE (high intensity intermittent exercise) group, a greater proportion of fat loss came from the hips, butt and thighs.

Now, what woman wouldn’t want that?? In an ideal world, I’d be able to take my saddle bags and stick them to my boobs but seeing as that machine hasn’t been invented yet, this seemed like a pretty good shot.

Downsides: The study was done on sedentary, overweight women. I’m not either so I know I can’t expect the same magnitude of results. The study also did nothing to control for diet. Were the women eating less? Maybe they were motivated to change up some unhealthy habits because they were being “studied”?? Who knows.

My Experiment: First of all, I had to change it a little bit (I know, ruins the point of replicating the study but shut up, I’m an experimental group of ONE which isn’t exactly reliable in the first place.). I’m an over-achiever and, apparently, a bad reader because when I originally read this article I thought it said to do 12-second sprints followed by 8-seconds of rest. You wouldn’t think the mix up would be a big deal (4 seconds ain’t a lot) but holy crap, I almost fell off the bike the first time I did it. 10 minutes and I was seeing stars. 15 minutes and I was doing Rorshach tests in the sweat droplets blanketing the floor and handlebars and only seeing water bottles and, strangely, snowflakes. 19.9 minutes and it was all I could do to find enough energy to stop pedalling long enough to collapse off the bike. I also realized later that the study said the subjects worked up to 20 minutes, which probably would have helped.

It got better. Thankfully. I’ve been doing the sprints 3 times a week (note the over-achiever part of the last paragraph) for 20 minutes and mostly have stayed with the backwards (and harder) 12/8 intervals.

My Results: I’m down 1.5% bodyfat. My weight is stable. I see hip bones where there were none before. I also reached my max heart rate ever of 187 when I did these sprints in conjuction with another 45-minute HIIT (high-intensity interval) routine. My resting heart rate is 42. No kidding. I torched 460 calories in 20 minutes (what I usually get in an hour of step aerobics). Plus, my butt looks better in my jeans. It might just be my imagination – won’t know for sure until I find a group of construction workers to walk past 10 or 20 times. Although I live in Minnesota so that might be problematic for two reasons 1) It’s Minnesota so even the cat-calls are polite and 2) It’s Minnesota and it’s November – how much construction is really going on?

Final Analysis: Unmitigated success! And I don’t say that often. (Not that you’d know – as this blog is one whole day old but keep reading and you’ll see.) I’m keeping the sprints. I might be in love with the sprints.

{ 6 comments… read them below or add one }

Alex November 6, 2007 at 12:49 am

It’s hard to argue with results like that!

I do have a few questions, though:

1. What was your fitness level before doing the sprints? Obviously, as you said, you are neither sedentary nor overweight – but how much cardio do you do per day or week?

2. How did you incorporate the sprints into your normal routine? Did they displace 20 minutes of what you used to do, or did you add the 20 minutes 3 times per week?

3. How long before you saw such great results?!


Charlotte November 6, 2007 at 8:35 pm

Holy Crap I have a READER!!! Wow, Alex, you’re my first reader – I think I might be in love with you.

That said, you ask some excellent questions and I’m going to put up a post to answer them.


Another Alex March 12, 2009 at 10:25 pm

A cousin of mine is working on this technique, he’s doing 30 minutes 3 days a week and so far got rid of 7 kilos in maybe a month…
I will try it, and tell you my advances…
So this really work
Cheers mate from down under land


Deb (Smoothie Girl Eats Too) September 3, 2009 at 12:18 am

OMG so funny. Can't believe this was your second post. Do you still do this (well, you're preggers now, but before that?) and do you feel that it's still effective.

I feel that when I do a lot of cardio I get friggin hungry!! Grrrrr! So the HIIT sounds like it might not spike the hunger?? Your thoughts?


Charlotte September 3, 2009 at 3:51 am

Deb – I have not done these since my first tri of pregnancy (now I'm so big that my knees hit my belly when I pedal a bike – HAWT) but up until then they were def. in the rotation.

I hadn't noticed a difference in my hunger levels between HIIT and steady state cardio. I'll have to think on it and ask my readers!


Fahri July 9, 2010 at 6:34 pm

Hey guys a read abt this before…………..this 20 min 8/12 sec sprint is a little shocking in practical as u think 20 min is not a grt deal. But it is……..I was sweating all over my face when i finished the first session. Let's see if there is any progress after a week!


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