Medium Intensity Interval Training (MIIT) Increases Fitness of Overweight Sedentary Women Slower, But Eventually Just As Effectively as HIIT. Neither Cuts Fat / Body Weight

It does not always have to be "all out", but 70% is probably the minimum for intervals - esp. for the non-obese.

If you know all SuppVersity articles by heart, the name Astorino may ring a bell. I mentioned a previous study by Todd A. Astorino in my 2012 article "Are You Still Burning Calories or Already Losing Fat? Study Shows: 5x15 Min HIIT Reduce Body Fat & Improve Fitness Twice as Effectively as 5x40min of Classic Cardio" (read more). In their most recent study, the researchers from the Department of Kinesiology at the California State University took another look at HIIT exercise for the average female US citizen, to be precise. And the observation they made is actually quite astonishing.

MIIT vs. HIIT: Can both be equally effective?

In this group of healthy sedentary (<1h/week of regular physical activity) women (n=30; age 18-40; BMI >35kg/m²) it did effectively not make a difference, whether the participants trained at a high or medium intensities.

As you can see in figure 1, over time, both workouts yielded the exact same increases in VO2Max (marker of cardiovascular fitness)., What is however significantly different is the slope and the general look of the VO2max graph.

Figure 1: Study design and results of the 12-week intervention; training was performed 3 days/week on a cycle ergometer and consisted of 6–10 bouts of 1 min duration at the given intensities; the asterisk after the week # indicates that the intensity values were adapted to the increase in W-Max over the past weeks (Astorino. 2013)

While the latter is clearly logarithmic for the high intensity interval training arm (HIIT; intensities see figure 1, left), the MIIT (LO in figure 1) VO2Max development is much more linear and does not display the same ceiling effect you see in the HI group. It would thus be reasonable to argue that...

MIIT hits HIIT, but...

... it is VERY likely that this is a "overweight woman phenomenon". After all, the heart rate was essentially the same regardless of whether the ladies worked out at an average intensity of 176W (MIIT) or 202W.

Figure 2: Heart rate and workload develoment over the 12-week study period (Astorino. 2013)

At first that may seem odd, but to push your heart rate through the 200 mark, you actually need a pretty decent fitness level. If you have been sitting around your whole life, you will be up to 190bpm when you simply take the stairs instead of the elevator; and while this is no health benefit it makes the same walk in the park that's just a nasty way of locomotion for the average athletic person an intense workout for the morbidly obese.

And what do we know about "intense workout"? Right, those are the true "cardio workouts" adaptation does not happen in the comfort zone and it does not entail weight loss (!) - I don't know how often I have to repeat that, but weight loss happens in the kitchen. You can only steer and promote what and how much you lose by working out... but that's the topic of another article.

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"Men are different women, too..." We all know that, but can we still train together or will women have to do cardio first, while men would be better off starting out lifting weights? (learn more)

Bottom line: If you, family or friends are starting out to work out - keep things at a pace that's intense for YOU - not for whomever you are trying to emulate or you are training with. If there is one beauty of doing cardio in the gym instead of outside, it is that you can train right next to a friend at your personal intensity level.

So don't put a spoke into your own wheels by trying not too look bad in front of a friend. Stick to your own tempo and use yourself as a reference to judge your progress - and if the latter looks like the orange graph in figure 2 (right) you know you are on track, no matter what the absolute wattage (or RPMs) say.

References:

• Astorino TA, Schubert MM, Palumbo E, Stirling D, McMillan DW, Cooper C, Godinez J, Martinez D, Gallant R. Magnitude and time course of changes in maximal oxygen uptake in response to distinct regimens of chronic interval training in sedentary women. Eur J Appl Physiol. 2013 Sep;113(9):2361-9.