Thursday, January 17, 2013

High Intensity Interval Training (HIIT) alternates low & high intensity activities. Example: alternate 30sec sprinting with 60sec jogging for 10-30mins. Spinning & Tabata are other popular forms of Interval Training.
But is HIIT really more efficient to lose fat than steady state cardio? In this post you'll get a comparison between both in terms of fat loss.

How Cardio Helps Fat Loss.
To lose fat you need a caloric deficit. Either by eating less calories or by burning more calories or both. Here's how HIIT & steady state cardio help you create this caloric deficit:
  • Burn Calories. Your body uses the food you eat as fuel for cardio. The more & higher intensity cardio you do, the more calories you'll burn.
  • Increase Metabolic Rate. Your body burns more calories at rest during the hours post cardio. This is the post-workout afterburn or EPOC.
  • Eat More. Cardio allows you eat more while having a caloric deficit. This can prevent starvation with lighter males/females.
There are more ways that cardio can help fat loss, but they don't matter within the context of this post. What matters is that you need a caloric deficit to lose fat (and you can do this without cardio, through dieting & lifting alone).

How Much Calories Does Cardio Burn?
Everything depends on the intensity at which you do cardio, and how long you do it. Here are some estimates:
  • Low Intensity. Less than 65% of your max heart rate. Walking burns only 5kcal/min. That's why it's not efficient for fat loss.
  • Moderate Intensity. 65-85% of your max heart rate. Steady state cardio at moderate intensity on the elliptical trainer burns about 10kcal/min.
  • High Intensity. +85% of your max heart rate. Sprints burn 15kcal/min. But most people can't sustain this kind of intensity for long.
These are estimates. The best way to find out how much you burn is using the bodybugg. And people who've used it, found that HIIT burns about the same or less calories than steady state cardio. 2 reasons:
  • Average intensity is the same since HIIT alternates between high & low intensities (sprints then jogging). So you end up burning 10kcal/min.
  • Most people never get the most out of HIIT because they aren't pushing themselves hard enough. Meaning: never until their muscles burn.

Then there's HIIT's biggest selling point: EPOC. According to this study HIIT has an EPOC of 14% vs 7% with steady state cardio. So if 30mins of HIIT burns as much as 30mins steady state cardio, that's 342kcal vs 321kcal.
Do 30mins HIIT 3x/week (which is a lot) and you'll burn 252kcal per month extra from EPOC. Since you need to burn 3500kcal to lose 1lb fat this is insignificant. But again, these numbers are estimates. Use the bodybugg for proof.
So in theory HIIT will burn more than steady state cardio through EPOC, but not as much as people usually think.

Cardio Duration.
The longer you do cardio, the more total calories you'll burn. You must be in really good shape to handle 30mins HIIT while anyone can do 45mins moderate intensity steady state cardio. Compare calories burned:
  • 30mins HIIT: burns 324kcal (incl 14% EPOC)
  • 45mins steady state cardio: burns 481kcal (incl 7% EPOC)
So you'll burn 628kcal/month more if you do 3x45mins steady state cardio than if you'd do 3x30mins HIIT. But people usually do 20mins HIIT. This would burn 228kcal incl EPOC or 3036kcal/month less. Which is almost 1lb of fat.

Cardio Frequency.
20mins of HIIT 3x/week is hard to recover from because it's high intensity. You will stall if you do StrongLifts 5x5 + HIIT 3x/week. But you can easily do steady state cardio 4x/week without issues.
4x45mins steady state cardio per week burns 7696kcal/month or +2lbs of fat. 3x20mins of HIIT only burns 2736kcal/month. So HIIT burns less total calories, is harder physically & mentally and causes stalling by messing with recovery.
Again: don't believe me. Get the bodybugg and do the test. Compare how many calories you burn with HIIT vs steady state cardio. Then decide what is most efficient knowing that burning more calories matters most to lose fat.

Should You Never Do HIIT?
No. HIIT has benefits: it takes less time, is more fun and more things I won't get into here. Did I write that you won't lose fat if you do HIIT? No, you will. But less than you might think.
My point is that for fat loss burning calories matters. Steady state cardio burns more calories and with less effort. Here are 5 quick cardio tips to lose fat:
  1. Don't do HIIT if you do StrongLifts 5x5. Your legs will never get enough recovery. Do steady state cardio only. Up to 4x45mins/week.
  2. Don't do HIIT if you're a beginner with zero fitness levels. This would be like starting with 220lbs on Squats. Build base fitness levels first.
  3. If you lack time to do 4x45mins/week steady state cardio, do 3x30mins. This burns about as many as calories as 3x30mins HIIT does.
  4. If you lack time to do 3x30mins/week steady state cardio, focus on diet & strength. You'll lose fat, but slower. Accept it.
  5. If you get bored of the steady state cardio: get over it. It's meant to be effective, not fun. Really. Once you've got body fat down you can quit it.
And the reason why Shaun T and his max interval training are so popular is because it exceeds the traditional HIIT 30mins. Also it is for more overall fitness rather than just fat lose. I personally do insanity from time to time and I think it is one of the best workouts out there to date. For one afterwards you are pooring in sweat and then you just have a feeling of accomplishment set in. So to each there own, however im gonna conclude with if you just want to loose fat then stick with steady state cardio, but if you want to build muscle along with lose some fat and have a little more fun, then HIIT or Insanity is the path for you.

-William Perdue
 Personal Trainer

No comments:

Post a Comment