• Courtney Ustrzycki

Just Burning Calories, or Losing Fat?

Study shows that doing 5x15m HIIT is twice as effective as 5x40m of steady state cardio to reduce body fat and improve cardiovascular fitness levels.


“Strong is the new skinny” is all over social media, and personally I think it’s becoming a little overrated. Some women are still unwilling to drop the cardio lifestyle and to pick up some heavy weights, but I definitely get it (I'll admit, I still like to do cardio sometimes!)


A recent study (references listed below) took 60 female students and simply told them that they need to lose weight. But here was the hook: they weren’t allow to change their current diets. They were divided into three categories:

  1. moderate intensity training: 40min of jogging or walking at 50% of the individual’s VO2max

  2. high intensity interval training (HIIT): 5x3min of running at 85% VO2max with 3min of active rest between the high intensity bouts

  3. sedentary control: no exercise at all

The exercise was performed on an outdoor track five times a week for 12 weeks.


We can agree that the 15 minutes of HIIT exercise took much less time than the moderate training, but HIIT group also provided:

  • a greater reduction in body fat

  • maintenance of lean mass

  • better waist-to-hip ratio

  • pronounced improvements in cardiovascular fitness (VO2Max)


Although this mentioned study was performed on overweight Chinese women, another recently published study (Astorino et al., 2012) shows that these results still occur similarly in both young men and women combined.


We can conclude from the above information that cardio is effective and should be performed to improve physique and overall fitness levels, it doesn’t have to be time consuming or kept within the ‘fat burning zone’ that most cardio machines suggest. The study continues to explain that 20-30 minutes of simple walking may actually help in resistance training recovery, and can be something that women should apply if they want to focus on improving their physique, look good and feel good about their bodies.


To find the right HIIT protocol for you, we’ll have to consider the type of strength/resistance training that you are currently applying to your weekly fitness regime. An easy way to think about it is, the more athletically ‘fit’ you are, the shorter the all-out bursts should be. The more body fat you carry, the longer the bout should extend. But remember, if you’re setting your bouts to more than :40 of all-out activity, chances are you aren’t performing it to the best of your abilities (you shouldn’t be able to sprint for more than :40!)


Subjects: 60 female overweight (BMI>25kg/m² and body fat >30%) university students


References:

Astorino TA, Allen RP, Roberson DW, Jurancich M. Effect of high-intensity interval training on cardiovascular function, VO2max, and muscular force. J Strength Cond Res. 2012 Jan;26(1):138-45

Ciolac EG, Bocchi EA, Greve JM, Guimarães GV. Heart rate response to exercise and cardiorespiratory fitness of young women at high familial risk for hypertension: effects of interval vs continuous training. Eur J Cardiovasc Prev Rehabil. 2011 Dec;18(6):824-30. Epub 2011 Feb 28.

Sijie T, Hainai Y, Fengying Y, Jianxiong W. High intensity interval exercise training in overweight young women. J Sports Med Phys Fitness. 2012 Jun;52(3):255-62.

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