Isn't High Intensity Interval Training (HIIT) For Everyone? Study Puts "!" Behind "Personalized Training" - Fitness, Fatness, Age & More Determine Its Effective- & Usefulness

Isn't HIIT for everyone? Study suggests: Effective- and usefulness of high intensity interval training depend on age and fitness level.

You will remember the two-part article serious about HIIT training "Making HIIT a HIT!" (Part I, Part II) I wrote back in 2012... you didn't well, although I would suggest you read it now, you will understand the idea of personalized HIIT training and there being no single optimal training regimen that works for everyone, anyways - right?

Good! Accordingly, you are not surprised that researchers from tie California State University San Marcos and the Griffith University at the Gold Coast in Queensland, Australia, teamed up to identify individual HIIT-responders and HIIT-non-responders.

You can learn more about HIIT at the SuppVersity

Never Train To Burn Calories!

Tabata = 14.2kcal /min ≠ Fat Loss

30s Intervals + 2:1 Work/Rec.

Making HIIT a Hit Part I/II

Making HIIT a Hit Part II/II

Triple Your Energy Exp.

The idea was to test whether there would be common denominators in those who do and those who don't respond with improvements in VO2max and lipid oxidation, as well as heart function and heart rate two commonly used modalities of interval training which have been previously-employed in the scientists lab.

"It was hypothesized that frequency of ‘‘non-responders’’ would be less than that typically reported after endurance training" (Astorino. 2014)

The ultimate goal obviously is the development of individualized exercise prescription which may help optimize responses to training and overall health status of various individuals.

In this particular case this meant determining whether the 20 habitually-active men and women who participated in part 1 of the study would show inter-individual as well as inter-group differences compared to the 20 non-obese sedentary women from part 2 of the study.

• In study 1, recreationally-active men and women underwent 2 wk of Wingate-based standardized interval treatment. At baseline and after completion of training, measures of VO2max, HR, and lipid oxidation were determined on separate days at least 24 h apart. Participants were required to maintain their habitual training status which was confirmed with a training log, and time of day was standardized within subjects across all trials. 

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  SuppVersity Suggested Read: "More HMB Free Acid Science: Now It's Also Good For High Intensity Interval Training (HIIT) Says the Latest Sponsored Trial W/Out Calcium HMB Control in Young Men & Women" | read more

  In study 2, sedentary young women completed 12 wk of a more tolerable form of interval training at intensities equal to 60–80% or 80–90%Wmax, during which these variables were assessed at baseline and every 3 wk of the study over two separate sessions. They were required to refrain from additional physical activity other than activities of daily living outside of the study. Exercise was performed at approximately the same time of day (#60 min) within participants. In both studies, body composition was assessed pre- and post-training using waist:hip ratio and sum of threeskinfolds (chest, abdomen, thigh for men and triceps, suprailiac, and thigh for women) following standardized procedures.

The fact that we are comparing the short-term effects (4–6 per day at intensities = 200–300%Wmax) over a 2 wk period.) in healthy trained men and women to the long-term effects of 3 d/wk of interval training for 12 wk (six to ten 1 min bouts of cycling at work rates equal to 60–80%Wmax or 80–90%Wmax) in untrained, but still healthy women is allegedly not 100% logical and reduces the significance of the results.

Figure 1: Changes in HR and fat oxidation in trained (left, part 1) & untrained (right, part 2) individuals (Astorino. 2014)

The latter is yet only true for the inter-group, yet not the intra-group comparisons, of which the data in Figure 1 leaves no doubt that it confirms the existance of responsers and non-responders to both regimen:

"Frequency of improved fat oxidation was similar (60–65%) across regimens. Only one participant across both interventions showed nonresponse for all variables." (Astorino. 2014)

Interestingly, the vaseline values of VO2 max, exercise HR, respiratory exchange ratio, and body fat were significant predictors of adaptations to interval training:

• Positive predictors of increases in VO2max were low baseline fitness (difficult to improve what's already top) and high effort during the wingate test.
• Positive predictors of improved heart rate was a high age and a high baseline heart rate
• Positive predictors of increases in fat oxidation were a low baseline physical activity and a low age.

In other words, the short-term wingate protocol (intense HIIT) is most beneficial for the lazy ones, in general and helps the elderly with heart health, and the young with increasing their fat oxidation. For the low intensity chronic regimen things were similar: Body fatness was another non-fitness related positive predictor of increases in VO2max and improvements in heart rate and fat oxidation.

I can only repeat my recommendations: If you are sedentary and obese, go slowly, it's likely you benefit much more from chronic low intensity interval training or even steady state exercise. If you are lean and athletic, HIIT it hard, but be careful! If you are also lifting weights, it may make more sense to do some regular cardio (LISS) and one or another plyometrics workout if ultimate leanness and the perfect body are your goals.

Bottom line: The study at hand does not deliver the promised experimental evidence one could use to program a personalized training regimen. In the end, it the design is just too limited to provide the corresponding information.

What the study did do, though, is confirm the already well-known associations between current effort and previous laziness with respect to the effective "gain" you can make in the gym or wherever else you may be working out: The lower your baseline fitness, the higher your fatness and the lower your activity levels the greater the impact of both: Low intensity long-term and high intensity short-term HIIT training. If you are the lean athletic type you will thus have to go really "high" on the intensity side to trigger a response... And maybe, just maybe, doing some LISS + weights is the better idea to get the body you're dreaming of, anyways. For me personally,it is the more sustainable way of training.

References:

• Astorino TA, Schubert MM (2014) Individual Responses to Completion of Short-Term and Chronic Interval Training: A Retrospective Study. PLoS ONE 9(5): e97638.