4x4 Minutes of HIIT Per Week That's All It Takes For Already Well-Conditioned Individuals to Stimulate Mitochondrial Growth ➯ 15% Increase in VO2Max, Peak & Mean Power

HIIT is a builder, not a burner - it builds the powerplants you need to burn.

For you as loyal SuppVersity readers, the fact that HIIT is the #1 growth promoter for your mitochondria is no news. That 4x4 minutes of HIIT per week are yet already enough to promote significant increases in the mitochondrial counterpart of mTOR, PGC-1α - the master regulator of mitochondrial biogenesis (Wu. 1999) - will probably still comes as a surprise. This is all the more true in view of the fact that these observations have been made in young, healthy, recreationally active adult men - not fat rodents, frail heart disease patients or sedentary type II diabetics.

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 corresponding study, which was conducted by researchers from the Queen’s University, the Kingston General Hospital and the University of British Columbia Okanagan, involved four weeks of "tabata style" high intensity interval training. The 4x4 training sessions consisted of 8x20s intervals separated by 10 s of rest. The equipment of choice was a Monark Ergomedic 874 E stationary bicycle ergometer with the resistance being set to 170% of the individual subject's peak aerobic power at 100 rpm.

Figure 1: Changes in performance parameters and protein + enzyme expression (Ma. 2013)

When you take a look at the changes, I want you to keep in mind that 19%, 14% and 13% increase in VO2Peak, peak aerobic performance and mean power during the Wingate test were the result of exactly 43min* of active exercise distributed across a 4-week timespan (*excluding the rest periods)... now that you've digested that, ask yourself: Is my training regimen anywhere near as effective? I mean, what was the result you got from the last 43 minutes you've been sweating in the gym?

While you are pondering this question, let's briefly take a look at the way Jasmin K. Ma, Trisha D. Scribbans, Brittany A. Edgett, J. Colin Boyd, Craig A. Simpson, Jonathan P. Little, and Brendon J. Gurd evaluate the results of their latest study and the differences to previous low-volume HIIT interventions:

Suggested: "Cardio or Weights? What Do Lean People Do to Lose 20% Abdominal Fat in 10 Weeks?" | more

"While other low volume HIT protocols have reported non-significant (Burgomaster. 2005, 2006) or small (below 10%) increases in aerobic capacity (Burgomaster. 2008; Hazell. 2010) the current protocol induced rela- tively large increases in both VO2peak (+19%) and an- aerobic performance (+12% - 14%). These findings con- firm the results of Tabata et al.(1996) who reported ele- vated VO2peak at both 3 and 6 wks of training, and demonstrate that increases in VO2peak occur following 2 wks of training. Interestingly, while VO2peak is traditionally believed to be determined by cardiac output, a recent report demonstrated increased VO2peak without an accompanying increase in maximal cardiac output following treadmill sprint interval training (MacPherson. 2011)."

In other words: You don't necessarily have to do "cardio" training to improve what people usually call your "cardiovascular fitness", when they actually mean your overall conditioning. In the end, that's similar to sports cars. If you build a sports car or formula one racer, the best engine is useless, when the gear can't transfer its power to the wheels. For humans that's not much different. It is thus only logical to accept Ma et al.'s hypothesis that the "elevated aerobic capacity following low volume HIT may be result from peripheral [and not central cardiovascular] adaptations." (Ma. 2013)

Bottom line + important reminder:  Despite the fact that the increase in citrate synthase (CitSyn; cf. Figure 1) didn't reach statistical significance, the overall increase in mitochondrial protein (COX I and IV) will still allow for an increase in fatty acid oxidation during exercise. If you still believe that HIIT sessions were mainly used to lose body fat you are totally off track. The total calorie expenditure is way too low to have any effect on your body fat levels.

The thing HIIT is good for is what you see in the study at hand. It's a mitochondrial builder that will ramp up PGC-1α, increases the mitochondrial firepower of your cells and promote the oxidative capacity of their power houses. How you use this increased "firepower", i.e. to run faster or longer or to burn a couple of additional calories while you are doing steady state cardio, play basketball or perform any other kind of aerobic activity to promote the baseline fat loss effects of your diet, is up to you, though.

References: 

• Burgomaster, K.A., Hughes, S.C., Heigenhauser, G.J.F., Bradwell, S.N. and Gibala, M.J. (2005) Six sessions of sprint interval training increases muscle oxidative potential and cycle endurance capacity in humans. Journal of Applied Physiology, 98, 1985-1990.  
• Burgomaster, K.A., Heigenhauser, G.J.F. and Gibala, M.J. (2006) Effect of short-term sprint interval training on human skeletal muscle carbohydrate metabolism during
  exercise and time-trial performance. Journal of Applied Physiology, 100, 2041-2047. 
• Burgomaster, K.A., Howarth,K.R., Phillips, S.M., Rakobowchuk, M., MacDonald, M.J., McGee, S.L. and Gibala, M.J. (2008) Similar metabolic adaptations during exercise after low volume sprint interval and traditional endurance training in humans. The Journal of Physiology,
  586, 151-160. 
• Hazell, T.J., MacPherson, R.E.K., Gravelle, B.M.R. and Lemon, P.W.R. (2010) 10 or 30-s sprint interval training bouts enhance both aerobic and anaerobic performance. European Journal of Applied Physiology, 110, 153-160.  
• Ma, J. K., Scribbans, T. D., Edgett, B. A., Boyd, J. C., Simpson, C. A., Little, J. P., & Gurd, B. J. (2013). Extremely low-volume, high-intensity interval training improves exercise capacity and increases mitochondrial protein content in human skeletal muscle. Open Journal of Molecular and Integrative Physiology, 3, 202.
• MacPherson, R.E.K., Hazell, T.J., Olver, T.D., Paterson, D.H. and Lemon, P.W.R. (2011) Run sprint interval training improves aerobic performance but not maximal cardiac output. Medicine & Science in Sports & Exercise, 43, 115-122.
• Wu, Z., Puigserver, P., Andersson, U., Zhang, C., Adelmant, G., Mootha, V., ... & Spiegelman, B. M. (1999). Mechanisms controlling mitochondrial biogenesis and respiration through the thermogenic coactivator PGC-1. Cell, 98(1), 115-124.